Submarine-fan systems i: characterization and stratigraphic prediction

Marine and Petroleum Geology 04 "0887# 578Ð606

Submarine!fan systems I] characterization and stratigraphic prediction M[ Richardsa\\ M[ Bowmanb\ H[ Readingc a

b

BP Exploration Alaska Inc\ P[O[ Box 085501\ Anchora`e Alaska 88497\ U[S[A[ BP Exploration Technolo`y\ Chertsey Road\ Sunbury on Thames TW05 6LN\ U[K[ c Department of Earth Sciences\ Parks Road\ Oxford OX0 2PR\ U[K[

Received 2 November 0884^ revised 3 November 0886^ accepted 04 November 0886

Abstract Submarine!fan and related deep!marine clastic systems such as submarine ramps and slope aprons are important hydrocarbon reservoirs in many parts of the world[ The origin and character of these systems re~ect a complex interplay between a range of autocyclic and allocyclic controls including sea!level ~uctuations\ basinal tectonics and the rate\ type and nature of sediment supply[ These controls are commonly interdependent[ This paper reviews the characteristics which distinguish di}erent submarine!fans and their subsurface prediction\ then proposes a classi_cation framework for fans which discriminates between di}erent systems on the basis of their fundamental controls[ The proposed classi_cation is discussed in terms of its value as a predictive tool in hydrocarbon exploration\ development and production[ A modus operandi is developed which uses the classi_cation for reservoir description and prediction and involves three stages of investigation] basin screening\ fan delineation and fan characterization[ Each stage demands the integration of a range of tools and techniques including sequence stratigraphy\ seismic facies analysis\ seismic redisplay and geophysical modeling[ These stages of analysis are linked\ in turn\ with core and wireline log data to constrain the range of possible fan types within a basin!_ll and assess the implications for reservoir seal and trap development[ This structured approach to stratigraphic analysis is also valuable in constraining the range of reservoir architectural options in appraisal\ development and production[ Þ 0887 Elsevier Science Ltd[ All rights reserved[ Keywords] Submarine fans^ Reservoir prediction^ Reservoir description

0[ Introduction Submarine!fan and related deep!marine deposits con! tain over 04) of the worlds total oil reserves in clastic! dominated hydrocarbon systems[ In the United Kingdom and Norwegian Continental shelves of the North Sea Basin and Atlantic Margin\ Palaeogene and Jurassic sub! marine!fan reservoirs account for × 84) and × 39) of all oil and gas production respectively "Illing and Hobson\ 0870^ Glennie\ 0873^ Brooks and Glennie\ 0874#[ These reservoirs are highly variable in geometry\ size and internal character\ leading to di}erences in reservoir architecture\ trapping style and in!place hydrocarbon volumes[ Much of this variability is directly related to the fundamental controls which in~uence the development  Corresponding author[ Tel[] 9933 0113 721999^ Fax 9933 0113 651888^ E!mail] richardmtÝbp[com

and characteristics of di}erent deep!marine clastic sys! tems "Fig[ 0#[ In exploration\ the principal objective of stratigraphic analysis for reservoir prediction must be to establish an understanding of the controls on deposition\ using them to identify potential sites of reservoir development in time and space\ together with the range of deep!marine clastic systems that might occur[ This is best achieved by using all of the geological and geophysical attributes of the systems in combination with a sound appreciation of the di}erent fan types and related systems and their controls[ For _eld appraisal and reservoir management\ analysis must focus upon accurate description of the 2D geometry and architecture "cf reservoir description# of ~ow units and non!reservoir lithologies within the reservoir envel! ope[ These detailed geological models are in turn trans! lated into accurate 2D representations of physical properties at interwell spacings "cf reservoir charac!

S9153Ð7061:87:,*see front matter Þ 0887 Elsevier Science Ltd[ All rights reserved PII] S 9 1 5 3 Ð 7 0 6 1 " 8 7 # 9 9 9 2 5 Ð 0

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Fig[ 0[ Controls on the development of deep!marine clastic systems[ The genesis of deep!marine clastic systems represents the end product of a complex interplay between a variety of autocyclic and allocyclic controls[ The controls are rarely mutually exclusive but commonly interdependent leading to a wide range of deep marine clastic deposits[

terization#[ These basic data sets are used as the frame! work for modeling recovery process\ sweep e.ciency and production performance by reservoir simulation\ as well as identifying drilling locations\ which will enable e}ec! tive and economic recovery of hydrocarbons[ The objective of this paper is two!fold] "0# To propose a classi_cation scheme that describes the variability observed in modern and ancient sub! marine!fans and related systems to account for the signi_cant di}erences in facies and sand body geometry encountered[ "1# To illustrate the value of the proposed classi_cation scheme for predicting stratigraphy and reservoir dis! tribution and for describing these reservoirs for _eld appraisal\ development and production[ 1[ Submarine!fan depositional models 1[0[ Historical perspective Over the last twenty years numerous attempts have been made to describe the variability of submarine!fan systems in order to provide predictive paradigms for out! crop and subsurface analysis "see detailed review in Read! ing and Richards\ 0883#[ In the 0869s\ in spite of the division of submarine!fan systems into coarse!grained\ canyon fed and _ne!grained delta!fed systems "Normark\ 0863^ 0867#\ or into e.cient and ine.cient fans "Mutti and Johns\ 0867#\ it was the single\ all embracing model

of Walker "0867# that attracted many explorationists and production Geoscientists[ Walker was well aware of the limitations of such a simpli_ed model "Nilsen\ Normark and Walker\ 0879#[ However\ its elegant simplicity led to its widespread use by the industry as a predictive tool in exploration and production[ This was largely because of the prevailing attitude to assess similarities\ rather than look for and recognize di}erences between fan reservoir targets and the {classical fan| model[ The industry|s gen! erally poor track record of exploration and exploitation of submarine fan plays and reservoirs during the 0869s can be often explained by applying this simplistic\ single model approach and further serves to demonstrate that there is no unique and universally applicable model that can be applied in the exploration for and exploitation of\ deep!marine clastic deposits[ In the 0879s\ the universality of the single point!source fans was questioned with the development of submarine ramp models "Chann and Dott\ 0872^ Heller and Dick! inson\ 0874# which described deep!sea clastic systems with multiple sources and feeders[ The subsequent pro! fusion of alternative models and lack of a coherent frame! work within which to characterize deep!marine clastic deposits and environments partly re~ected a growing awareness by many workers\ of the variability in fan systems "sensu Walker\ 0867^ Nilsen\ Normark and Walker\ 0879^ see Bouma\ Normark and Barnes\ 0874# in terms of their sediment composition and feeder type "viz _ne!grained delta fed vs coarse!grained canyon!fed fans] Normark\ 0863^ 0867^ 0879^ Stow\ 0875^ Busby! Spera\ 0874#[ Today\ the prevailing trend in subsurface exploration is to use the term {submarine!fan| to embrace all deep! marine clastic turbidite systems[ In this paper we follow the scheme of Reading and Richards "0873# which restricts the use of the term submarine!fan to single point! source turbidite systems[ Related multiple point!sourced systems such as submarine ramps and aprons are included with submarine!fans under the general umbrella of deep! water clastic depositional systems[ We believe that this approach will encourage explorers to be more imagin! ative and to evaluate plays without the constraints imposed by restrictive de_nitions and a limited number of idealized models[ The approach also demands that interpreters remain aware of the range of possible options and the need for an objective and pragmatic approach to any investigation\ based primarily upon observation and interpretation of data[ Initial attempts to describe the variability of sub! marine!fans and related systems within the framework of a classi_cation scheme were based on fan geometry "Stow\ 0875# and transport e.ciency "Mutti\ 0868#[ Both of these schemes have limited value as predictive tools for subsurface exploration and exploitation[ The geometry of a submarine!fan is controlled by the geometry of the receiving basin\ rather than the intrinsic

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characteristics of the fan[ Indeed\ external fan geometry provides little information on the internal reservoir character of the system "viz sand body geometry\ net: gross ratio\ etc[#[ This means that fans of similar geometry do not necessarily have a similar genesis or internal characteristics[ Characterizing fans on the basis of transport e.ciency is equally untenable as a predictive tool[ Transport e.ciency of a fan is controlled by the rheological proper! ties "grain:water interactions and ~ow# of the ~ow and not the fan system itself[ Whilst it can be argued that such a scheme is applicable to modern fans\ its validity for describing ancient systems must be considered interpretative at best\ because the mechanism of sediment transport can only be inferred from ancient sequences[ Notwithstanding these problems\ the concept of trans! port e.ciency is a valuable tool for providing a predictive link between the type of sediment available within a source area and the locus of sand deposition within a basin "Mutti\ 0868^ Lowe\ 0871^ Nelson and Nilsen\ 0873^ Reading and Richards\ 0883#[ The concept of transport e.ciency used with caution\ provides a simple {rule of thumb| for assessing the likely site of sand deposition given a knowledge of source area sediment type "Fig[ 1#[ In general\ turbidity currents accessing a wide range of grain size and detrital min! eralogy "e[g[\ ~uvial or ~uvio!deltaic source areas# will transport sediment signi_cant distances[ Coarse grains will be supported by "a# increased ~uid turbulence\ "b# hindered settling due to their own high concentration\ and "c# the buoyant lift provided by the interstitial mix! ture of water and _ne!grained sediment "Lowe\ 0871#[ Such turbidity currents exhibit high transport e.ciency "Mutti\ 0868^ Mutti and Normark\ 0876#[ For simply structured basins\ the principal locus of sand deposition associated with such high e.ciency turbidity currents should logically lie some distance from the base of the submarine slope "Fig[ 1c#[ Turbidity currents which access well sorted sediment with restricted grain popu! lations "e[g[\ relict shelfal:and marginal marine sands# will not transport sand far because of the absence of _ne! grained lubricating material in the ~ow which leads to a reduction in ~uid density\ ~uid buoyancy and turbulence "Lowe\ 0871#[ These are the low e.ciency systems of Mutti and Normark "0876#[ The limited transport e.ciency means that the locus of sand deposition within the fan will be close to the base of the submarine slope "Fig[ 1a#[ More recent studies assess the variability of submarine! fans within the wider context of collective facies models for deep!marine clastic systems[ They demand an under! standing and awareness of the various factors which con! trol di}erences in lithological character\ sand body geometry and constituent architectural elements "Read! ing and Orton\ 0880^ Reading 0880\ Reading and Rich! ards\ 0883#[ In essence\ facies models for submarine!fans

580

have evolved in a similar manner to those of deltaic depositional systems where the emphasis has switched from a single predictive paradigm through a process! related ternary classi_cation "Galloway\ 0864#\ to one that also incorporates variability in grain size using a triangular prism "Orton and Reading\ 0882#[ 1[1[ Classi_cation of deep!marine clastic systems The classi_cation framework proposed here forms a basis for stratigraphic prediction and description of deep! marine reservoir systems "see also Richards and Bowman\ 0887\ in press#[ The framework is a continuum in which a number of end!member or basic models are de_ned[ Each represents one of a series of hybrid associations of fan types\ acting as either a normative model or a _xed point for comparison[ Each can be modi_ed to suppress or emphasize speci_c features of an individual fan[ A detailed review of the end!member classi_cation sch! eme is presented elsewhere "Reading and Orton\ 0880^ Reading\ 0880^ Reading and Richards\ 0883#[ In contrast to the two dimensional table used in the previous papers\ here the classi_cation framework is expressed as a con! tinuum of two dimensional ternary diagrams linked in the third dimension by the parameter of dominant grain size "Fig[ 2#[ Four end!member groups are identi_ed] "0# gravel!rich\ "1# sand!rich\ "2# mixed sand!mud and "3# mid!rich systems[ The apices of each ternary diagram mark the nature of sediment supply and the number of entry points feeding a system[ This enables distinction between single point!source submarine!fans\ multiple point!source submarine ramps\ and line!sourced slope apron systems following the terminology of Reading and Richards "0883#[ This framework enables description and assessment of a wide range of variables within a fan[ It also illustrates how changes in the method of sediment supply to a basin\ the distribution of entry points and the overall grain size of potential provenance areas exert a profound in~uence on the resulting deep!marine clastic systems\ notably in their reservoir\ seal and trapping characteristics[ The key characteristics and attributes of the four groups of deep! marine clastic systems are summarized below and illus! trated in Figs 3Ð6[ Summaries and models are derived from proprietary subsurface and outcrop studies carried out by BP Exploration together with data consolidated from the published literature[ It is important to emphasize that the framework describes a continuum and contains an almost in_nite variation in fan types[ The end!member models provide a basis for characterizing the general features of a par! ticular fan type "sand!rich\ mixed sand!mud\ mud!rich\ etc[#[ These models represent a distillation of the general features of a system and will not accurately characterize the actual variability in facies\ geometry and architecture of a speci_c system[ The end!member models are of most

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Fig[ 1[ Summary diagram illustrating the concept of transport e.ciency and its relationship to the locus of coarse clastic deposition within a basin[

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Fig[ 2[ Classi_cation of submarine!fans by "a# sediment supply mechanism\ "b# dominant grain size and "c# number of entry points "Modi_ed after Reading + Richards\ 0883#[

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Fig[ 3[ Summary block diagrams illustrating the range of gravel!rich deep marine clastic systems including "a# aprons\ "b# submarine fans and "c# submarine ramps "After Reading + Richards\ 0883#[

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Fig[ 4[ Summary block diagrams illustrating the range of sand!rich deep marine clastic systems including "a# aprons\ "b# submarine fans and "c# submarine ramps "After Reading + Richards\ 0883#[

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Fig[ 5[ Summary block diagrams illustrating the range of mixed sand!mud deep marine clastic systems including "a# aprons\ "b# submarine fans and "c# submarine ramps "After Reading + Richards\ 0883#[

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Fig[ 6[ Summary block diagrams illustrating the range of mud!rich deep marine clastic systems including "a# aprons\ "b# submarine fans and "c# submarine ramps "After Reading + Richards\ 0883#[

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Table 0[ Reservoir characteristics of contrasting types of deep!marine clastic system "After Reading + Richards\ 0883#[ Feeder System Type

Point Source Submarine Fans

Dominant Grain Size category

Mud MF

Multiple Source Submarine Ramps

Mud:Sand MSF

Sand SF

Gravel GF

Mud MR

Mud:Sand MSR

Principal architectural elements Proximal area Channel!levees Distal area Distal sheets Seismic architecture Channel!levees\ Distal parallel re~ectors

Channel!levees Lobes Channel!levees and Mounds

Channels Channelised!lobes Constructional\ low relief mounds

Wedges Distal sheets Wedges

Channel!levees Lobes Channel!levees and Mounds

Sand percentage

¾ 29) sand

− 29Ð ¾ 69) sand

− 69) sand

Sandbody geometry

Large\ lenticular channels with multiple\ variable scale sand\ silt and mud _lls[ High degree of heterogeneity[ Distal fan dominated by thin sand\ silt and mud sheets[ A\B\E\F High

Lenticular channels dominated by sand or mud!_ll[ Down!dip lobes formed of interbedded and alternating sand\ silts and muds[

Moderate size sandbodies within overall large channel form[ Sands commonly isolated in both down!dip and up! dip directions[

C\D High!Moderate

Variable 4Ð49) " × 49) gravel# Broad sheet!like to low Irregular relief lobate sandbody interconnected gravels[ geometries dominated Proximal areas internally by dominated by channelised sandstone conglomerates and units[ breccias[ Sands dominant within medial to distal parts of system[ B\C A\B\F Low High

Channel!levees Distal sheets Channel!levees and Distal parallel re~ectors ¾ 29) sand

A\B\E\F High

O}set stacked\ lenticular channel sandbodies bounded by levee _nes\ passing down!dip into o}set stacked lobate sandbodies formed of sandstones and mudstones[ C\D High!Moderate

Poor Poor Stratigraphic

Moderate Poor Stratigraphic

Good Good Structural

Good Poor Structural

PoorÐModerate Moderate Stratigraphic

Moderate Moderate Stratigraphic

"0# Up!dip pinchout of inter fan channel sandstones

"0# Structural trapping of fan conglomerates adjacent to footwall scarps

"0# Stratigraphic "0# Combined trapping within terminal structural! lobes stratigraphic trap in proximal ramp channels "1# Stratigraphic "1#Up!dip pinchout of trapping of channel channel and:or ramp levee:splay sands lobe sands

Turbidite facies Reservoir heterogeneity Sandbody communication Vertical Lateral Common reservoir trap type Play concepts

Key exploration risks

Importance and position on relative sea level cycle

"0# Stratigraphic "0#Stratigraphic trapping within terminal trapping of channel + lobes lobe deposits

− 29Ð ¾ 69) sand

"1# Stratigraphic trapping of channel levee and splay deposits Reservoir and trap presence\ extent and identi_cation

"1# Trapping of sands "1# Stratigraphic in canyons from slope trapping of mid!fan failure + ~ow stripping channelised lobes

"1# Structural trapping of medial:distal sandstones

Reservoir presence\ extent + identi_cation\ seal integrity

Trap requires structural component^ Seal integrity

Reservoir quality and seal integrity

Reservoir quality\ trap presence\ extent and identi_cation

Reservoir de_nition\ delineation and quality^ seal integrity

Important lowstands

Potentially important HST LST

Not important

Not important

Important LST

Potentially

value in basin and play fairway exploration[ For devel! opment and production\ the end!members would be either discarded or modi_ed to re~ect the particular character of a submarine!fan reservoir[ At a broad scale\ each of the systems illustrated in Fig[ 2 displays a predictable arrangement of architectural elements\ sand body geometries and depositional facies[ These in turn in~uence seismic architecture\ acoustic expression\ and wireline character of a system\ together with sand body geometry\ reservoir architecture and fac! ies recognized in core[ The key reservoir characteristics of each fan type are described in Table 0 "After Reading and Richards\ 0883#[ Submarine!fans and ramps appear to relate to more stable drainage:feeder systems[ They tend to display organized and relatively predictable internal architecture and facies distributions[ As a result\ they often form primary targets for hydrocarbon explo!

ration in a basin[ In contrast\ slope aprons are more often associated with slope failure\ local sediment sources and:or ephemeral drainage and feeder systems[ This results in greater internal facies variability and dis! organization[ They typically form less attractive targets for early exploration within a basin[ This is especially true of mud!rich and mixed sand!mud slope aprons[ These latter deep!water clastic systems may provide tar! gets during a mature phase of basin or play fairway exploration[ 1[1[0[ Gravel!rich systems Gravel!rich systems are commonly the down!dip mar! ine equivalents of coarse!grained fan!delta\ alluvial cone and braid plain environments "Fig[ 3#[ They are associ! ated with high slope gradients[ Examples are generally small scale and localized "up to 49 km in radius#[ They are

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Linear Source Slope Aprons Sand SR

Gravel GR

Mud MA

Mud:Sand MSA

Sand SA

Gravel GA

Channels Channelised!lobes Constructional\ Low Relief Mounds

Wedges Distal sheets Wedges

Slumps\ slides

Slumps\ slides O}set lobes Chaotic Mounds

Channels Slumps Mounds

Wedges Debris ~ows Wedges

− 69) sand

Variable 4Ð49) " × 49) gravel# Broad sheet!like to low Irregular relief lobate sandbody interconnected gravels[ geometries dominated Proximal areas internally by dominated by channelised sandstone conglomerates and units[ breccias[ Sands dominant within medial to distal parts of system[ B\C A\B\E\F Low High

Chaotic Mounds

Highly variable 9Ð19) Highly variable 9Ð19) Highly variable

Highly variable

Limited sand development[ Commonly con_ned to slide scars and slump generated lows[

Laterally extensive separated by silts and muds

Lobate sandbodies dominated by interconnected channelised units

Laterally extensive distally limited

F High

D\F High!Moderate

D\E Low

A\B\F High

Good Good Structural

Good Moderate Structural

Poor Poor Stratigraphic

Moderate Moderate Stratigraphic

Very good Very good Structural

Good Very good Structural

Combined structural and stratigraphic traps of ramp sandstones

"0# Structural trapping of fan conglomerates + sandstone against to footwall scarps

Stratigraphic trapping of detached slumped clastics derived from active orv relict up! dip deltaic systems

Stratigraphic trapping of detached slumped clastics derived from active or relict up!dip deltaic systems

Combined structural and stratigraphic traps involving slope apron turbidite sandstones

Structural closure of fan conglomerates and sandstones against to footwall scarps

Reservoir and trap presence\ extent and identi_cation^ seal integrity Highly important HST

Reservoir and trap presence\ extent and identi_cation^ seal integrity Low importance HST + LSW:TST

Trap requires structural component^ Seal integrity

Reservoir quality and seal integrity

Low importance\ LST:LSW

Low importance\ LST

"1# Structural closure of media:distal sandstones Trap requires structural component^ Seal integrity

Reservoir quality and seal integrity

Not important important HST

Important LST HST\ LST +TST

characterized internally by complex and irregular gravels and sandstones with a high degree of facies variability "Reading and Richards\ 0883#[ Net sand and gravel ratios are typically high and reservoir connectivity good[ Res! ervoir trapping mechanisms developed within gravel!rich systems are dominantly structural[ 1[1[0[0[ Gravel!rich slope aprons[ Gravel!rich slope aprons most commonly develop adjacent to submarine fault scarps where sediment is derived from reworking\ wasting or catastrophic submarine rock fall "Fig[ 3a#[ Systems are broadly analogous to linear\ fault controlled colluvium slopes and talus cones in subaerial settings[ Ephemeral input from up!dip alluvial fans and fan deltas may provide an additional coarse clastic component to the apron[ Few examples of these systems have been documented from either modern deposits or the geo!

logical record "Case\ 0863^ Prior and Bornhold\ 0877^ Surlyk\ 0867^ 0873#[ As a result\ the physiographic elements and internal architecture are poorly understood[ The limited studies suggest that systems show varying degrees of facies heterogeneity "Prior and Bornhold\ 0877^ Surlyk\ 0867^ 0873#[ On seismic\ such systems form wedge shaped aggra! dational packages which are thickest adjacent to footwall scarps[ Internal seismic character is generally poor because of a lack of acoustic contrast in these disor! ganized\ but predominantly coarse!grained deposits[ Reservoir potential is largely controlled by the litho! logical character of the footwall areas\ together with any input from adjacent brain plain:fan deltas[ Close prox! imity to provenance areas combined with poor sorting within the systems commonly results in poor to moderate reservoir quality[ Exploration for these systems has

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achieved little success to date[ This is largely due to the high risk on reservoir presence and e}ectiveness[ Exam! ples of such systems include the early stages of the late Jurassic "Brae trend# and early Palaeogene "T19 Mau! reen# submarine!fan and ramp complexes of the North Sea Basin[ 1[1[0[1[ Gravel!rich submarine!fans[ Single point!source gravel!rich fans are well documented in the Recent\ where they commonly form the down dip of coarse!grained fan deltas and alluvial cones "Fig[ 3b^ e[g[\ Ferentinos et al[\ 0877] Colella and Prior\ 0889^ Piper et al[\ 0889^ Prior and Bornhold\ 0889#[ Systems are commonly associated with active margins\ most notably rift and wrench related basin settings[ The extent of fan deposition depends upon maintaining slope gradients by faulting as well as access to source areas dominated by coarse!grained clastic material "Prior and Bornhold\ 0889#[ Gravel!rich fans most often develop where sediments are supplied through transfer segments o}setting basin boundary faults[ Morphological elements of the fan are rarely dis! tinguishable[ They display a down!slope grain size reduction from proximal conglomerate\ gravel\ talus and debris!~ow units next to fault wall scarps\ to more sandy lithofacies at the margins of the fan where the transition from reservoir to non!reservoir lithofacies is generally abrupt[ Lithofacies distribution within the fan system is highly variable because of the complex interaction of rock fall\ high!density turbidity currents and inertial ~ows in transporting coarse! and _ne!grained material across the fan surface "Prior and Bornhold\ 0889#[ Documentation of ancient gravel!rich fans is sparse[ Limited unpublished information indicates that the seis! mic character of these systems are broadly comparable with slope aprons[ Individual fans are imaged seismically as localized wedge!shaped packages with poor internal acoustic character[ The wedge thickens into hanging! wall areas\ often adjacent to up!dip transfer segments[ Proximal facies are generally of limited reservoir poten! tial\ and are dominated by rockfall\ debris ~ow and gra! vel!rich turbidites[ Reservoir facies are most commonly developed within the medial and outer parts of the fan where gravel!rich facies give way to more sand!rich tur! bidites[ 1[1[0[2[ Gravel!rich submarine ramps[ Coarse!grained submarine ramp systems are well documented in the geo! logical record[ As described here\ they are analogous to apron!fringe and slope!fringe fan systems described by some authors "e[g[\ Westcott and Etheridge\ 0872^ Turner et al[\ 0876^ Colemenero et al[\ 0877^ Fig[ 3c#[ The multiple nature of active feeders to these systems is caused by periodic switching of gravelly fan!deltas or coalescing alluvial fans along active basin margins[ The seismic character\ proximal to distal facies variability and down!

dip changes in net]gross of these systems is similar to that of gravel!rich fans[ Proximal portions of the ramp often exhibit poor res! ervoir quality\ particularly where alluvial fed systems are intermixed with material derived from rock fall and debris ~ows[ Strike sections through the ramp system are highly variable because of the complex interaction of a range of sediment gravity!~ow processes and the in~u! ence of faulting on facies patterns and sediment transport paths[ In the late Jurassic Brae area _elds of the South Viking Graben in the North Sea Basin "Stow\ 0874^ Turner et al[\ 0876^ Wood and Hall\ 0882# the best res! ervoirs lie within the medial ramp where sand!rich tur! bidites predominate[ 1[1[1[ Sand!rich systems These contain more than 69) sand "Fig[ 4#[ This boundary is not arbitrary^ it marks a major change in seismic character\ reservoir architecture and trapping geometry\ distinguishing the sand!rich systems from their gravelly and muddier counterparts[ Sand!rich systems are typically small "generally 0Ð49 km radius# being sourced from either incision or failure of relict sand!rich shelves or by direct canyon access to littoral drift cells[ Because of their net reservoir volume\ trapping mechanisms are predominantly structural[ 1[1[1[0[ Sand!rich slope aprons[ These develop where sediment is delivered along a broad front adjacent to the submarine slope[ Sediment accumulation is essentially continuous\ forming a linear belt which parallels the slope margin[ Sands may be delivered by direct feed from an up!dip sandy coastal braid plain\ mass wasting and reworking of a sandy shelf!slope margin or by periodic ~ushing of sand through basin!margin incision "Fig[ 4a^ Reading and Richards\ 0883#[ Distinguishing sand!rich slope aprons from ramps is not easy[ It is suggested here that ramp be used as the descriptor\ unless there is unequivocal evidence of an apron system[ Modern sand!rich slope aprons are uncom! mon^ when developed\ they appear to be small!scale and produced by shelf!slope failure and mass wasting[ Larger scale systems could potentially develop in response to reworking of topset systems such as sandy coastal braid plains during periods of relative sea!level fall[ At these times\ sediment ~ux to the basin may be high because of steeper slopes and enhanced alluvial gradients[ No well calibrated subsurface examples of sand!rich slope apron reservoirs have been published to date[ Unpublished studies suggest that they form lobate\ often aggradational\ wedged shaped seismic packages with rare and often poorly de_ned internal clinoforms[ Examples typically bank up against basin slopes[ Principal reservoir facies occurs in proximal areas close to the basin margin[ Components of the Stevens Fan complex in the San

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Joaquin Basin\ California are considered here as can! didate sand!rich aprons[ 1[1[1[1[ Sand!rich submarine fans[ These are single point! source feeder systems where the canyon or entry point taps a sand!rich provenance "Fig[ 4b#[ They equate with the low e.ciency\ sand!dominated fans of many authors "Normark\ 0867^ Link and Nilsen\ 0879^ Nilsen\ 0879^ Mutti\ 0874^ Busby!Spera\ 0874#[ Examples are typically aggradational with the principal site of sand deposition occurring close to the base of the submarine slope "Mutti\ 0874#[ Fans are commonly connected via canyons to active sandy nearshore littoral drift cells[ They may also be produced by reworking relict sand!rich deltaic and shelfal systems[ Sand!rich fans are often small!scale\ subtle features rarely exceeding 099Ð199 m thickness[ They display single\ mounded to sheet!like seismic packages with either opaque internal character or poorly developed parallel to sub!parallel re~ectors[ Sand!rich fans fed by littoral drift cells tend to be localized\ small accumulations caused by the low volume of sediment available to the basin "e[g[\ the Redondo Fan] Haner\ 0860#[ In contrast\ larger volume systems are often associated with major slope incision or failure and contemporaneous erosion or wasting of a sand!dominated shelf "e[g[\ Frigg Fan] Heritier et al[\ 0868^ McGovney and Radovich\ 0874#[ In such examples\ signi_cant volumes of coarse!grained shelf clastics may be carried into the basin[ Sand!rich fans comprise an inner fan often dominated by a single feeder channel[ This is linked down!dip with numerous bifurcating:braided distributary channels[ The mid!fan or suprafan area is de_ned by the down!dip change from channels to channelised fan!lobes "Link and Nilsen\ 0879^ Nilsen\ 0870#[ The low volume of _ne!grai! ned material within these systems prevents the devel! opment of con_ned and stable channels[ This imparts an overall braided character to the fan surface with the formation of both sheet!like and lobate sand bodies "Belderson et al[\ 0873^ Nelson and Nilsen\ 0873^ Busby! Spera\ 0874^ Kleverlaan\ 0878#[ The transition from mid fan to basin plain "outer fan# is generally abrupt\ in con! trast to muddier fan systems[ Sand!rich fan systems form excellent reservoirs[ Many of the most proli_c fan reservoirs of the North Sea Basin are of this fan type "e[g[\ Balder fan] Sarg and Skjold\ 0871^ Magnus fan] De|Ath and Schuyleman\ 0870^ Miller fan] Garland\ 0882^ Frigg fan] McGoveny and Radovich\ 0874^ Forth fan] Alexander et al[\ 0880#[ 1[1[1[2[ Sand!rich submarine ramps[ Sand!rich submarine ramps are the basinal component of prograding sandy deltas or coastal plains with narrow shelves "Fig[ 4c#[ Sediment is carried over a broad front by multiple feeder systems which incise as they transverse the shelf!slope break[ Ramp development is predominantly aggra!

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dational because of high rates of sediment input from the up!dip deltaic or coastal systems[ Depositional models for sand!rich submarine ramps commonly separate the system into distinct physiographic elements "Link and Welton\ 0871^ Chann and Dott\ 0872^ Heller and Dick! inson\ 0874#[ Here we recognize the subaerial delta! :coastal plain\ proximal\ medial and distal ramp[ The proximal ramp is dominated by ephemeral channels feed! ing small\ ca 09 km wide\ slightly elongated lobes[ The medial and distal ramps are dominated by increasingly _ne!grained sand!rich turbidites which pass abruptly into basin plain muds[ Sand!rich ramps commonly form linear\ sheet!like seis! mic packages that extend basinwards from the shelf as elongate belts\ parallel to the shelf!slope break[ Internal seismic character is generally poor\ although low!angle dipping\ sub!parallel or parallel re~ectors may be present[ The internal acoustic character of these systems is similar to single point!source systems "cf Fig[ 4c#[ The sand!dominated nature and sheet!like geometry of potential reservoir lithologies limits the potential for developing stratigraphic traps[ In general\ e}ective trap! ping geometries require a combination of complete aban! donment of the fan system combined with some component of structural closure for trap integrity "e[g[\ Claymore and Galley Fields] Boote and Gustav\ 0876#[ 1[1[2[ Mixed sand!mud systems These form a continuous spectrum from more sandy to muddy systems with sand ] shale ratios ranging between 29Ð69) "Fig[ 5#[ They are typically moderate scale features "4Ð099 km radius#\ often being a product of erosion\ failure and:or direct sediment input from large mixed load delta\ shoreline and coastal plain systems[ They account for a major proportion of published ancient deep!marine clastic successions[ Systems are typically highly organized with discrete well developed architectural elements of which channel! levee complexes and lobes are most important[ In general\ increasing mud content results in a reduction of topo! graphic relief and increasing importance of channel!levee complexes as the principal architectural element[ Trap! ping mechanisms within these systems range from wholly structural to stratigraphic con_gurations[ 1[1[2[0[ Mixed sand!mud slope aprons[ These are com! monly associated with passive continental:basin margins where sliding\ slumping and mass wasting of the slope and outer shelf provide the main mechanism for lib! erating detritus into the basin "Fig[ 5a#[ Sediment failure is caused by a range of mechanisms of which seismic activity\ excess pore water pressure in response to active sediment loading and over steepening of submarine slopes are most important[ Sands may also be carried basinwards through ephemeral feeder systems or con! duits caused by failure of the basin margin[ Local slump

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topography within the apron can lead to localized accumulation of ponded turbidites[ Slope aprons are often precursors to more con! ventional submarine!fan systems because slope failure is an important mechanism for initiation of long!lived major canyon systems in poorly lithi_ed substrates[ Hence\ the common association of slope aprons with conventional mixed sand!mud fan and ramp deposits[ The characteristics of these systems are comparable to recent and ancient slope and debris aprons "Field and Clark\ 0868^ Nardin et al[\ 0868^ Nelson\ 0872^ Surlyk\ 0876^ 0878#[ The nature of depositional processes within the slope aprons results in a highly irregular distribution of litho! facies[ Systems often appear as well developed mounded seismic packages dominated internally by hummocky to chaotic re~ectors "Nardin et al[\ 0868#[ The mounds are typically located near the base of a submarine slope[ Such systems are often mistaken for more organized sub! marine!fan or ramps with greater hydrocarbon potential[ Mixed load aprons carry a high risk on reservoir presence\ quality and continuity[ Potential exploration targets exist where extensive failure either exhumes coarse!grained relict shelfal deposits or provides gullied or facilitates the development of ponded intraslope feeders "Surlyk\ 0876#[ 1[1[2[1[ Mixed sand!mud submarine!fans[ These are rep! resented by many of the more classical submarine!fan systems described in both the recent and geologic record "e[g[\ Mutti and Ricci!Luchi\ 0864^ Normark\ 0869^ Nor! mark\ Piper and Hess\ 0868^ Droz\ 0872^ Droz and Bellaiche\ 0874# together with the fan model of Walker "0867^ 0874#[ Systems are commonly linked to mixed load ~uvial and ~uvio!deltaic systems via feeder channels and slope related canyons "Fig[ 5b#[ The fan is divided into upper\ middle and lower elements[ The upper fan is typically dominated by a single feeder channel ~anked by mud!dominated levees[ These pass down!fan and bifurcate into highly sinuous or meander! ing distributary channels which form conduits for the transport of coarse!grained clastics to the middle and lower fan[ Unpublished subsurface data from ancient inner fan!channel systems suggest a wide spectrum of channel _lls produced by a combination of gradual aban! donment and back!_lling\ or rapid abandonment and in_ll by slumping from the channel levee margins and adjacent basin slopes[ Characterization of the inner fan channel _ll is critical for assessing up!dip seal integrity to exploration prospects[ The mid!fan0 area forms the aggradational part of the fan system[ It comprises a series of distributary channels

which pass down!dip into lobes[1 Mid!fan aggradation is a result of intermittent and repeated switching of dis! tributary channels\ their abandonment and lateral stack! ing of depositional lobes "Walker\ 0867#[ Lobe systems are well developed because the levees stabilize channel courses and thereby focus turbidity currents onto the mid!fan[ The outer fan forms a low gradient topographically smooth area characterized by deposition of _ne!grained\ dilute turbidites and hemi!pelagic material[ Rapid incision of mid!fan channels can lead to by!passing of the mid!fan and the development of small lobes within the outer fan "Walker\ 0867#[ The volume and scale of mixed sand!mud fans depends upon the mechanism of sediment supply[ Systems com! monly develop at a distance from the base of slope re~ecting their e.ciency in delivering coarse clastics to the basin[ Systems fed by coeval mixed!load deltas are commonly smaller and less easy to resolve seismically[ Large volume systems commonly occur down!dip from and are temporally equivalent to major unconformities "sequence boundaries# at a basin margin[ Inner!fan channels are distinguished seismically where su.cient impedance contrast exists between the levee\ channel!_ll and background hemi!pelagic material[ They are generally small scale and often {missed| by interpreters[ When observed\ they display poor to well! developed wedge shaped or {gull wing| geometry domi! nated by low!angle re~ectors\ which downlap towards the margins of the fan system[ The mounded seismic character of mixed sand!mud fans contrast with that of sand!rich systems where the mound often re~ects the whole fan system\ rather than one or more of its component architectural elements[ In mixed load systems\ depositional lobes and channels on the mid!fan develop away from the base of slope[ They show poor to well developed hummocky seismic charac! ter\ appearing as isolated mounds away from the base of slope[ The stacked nature of lobes separated by acous! tically re~ective abandonment shales commonly leads to complex clinoform units within the overall seismic envel! ope of the fan[ 1[1[2[2[ Mixed sand!mud submarine ramps[ These are commonly associated with mixed sand!mud deltaic systems\ which advance across subdued shelf!slope breaks during active basin margin progradation[ They may also result from focusing or reworking of mixed sediment loads carried basinwards through multiple slope valley systems "Fig[ 5c# similar to the en!echelon channel! levee complexes of the modern Ebro!fan system "Nelson et al[\ 0874^ Nelson and Maldonado\ 0877#[ The ramp is

0

The term {{suprafan|| has been used extensively in historical litera! ture to denote the mid!fan area[ The suprafan term is now become obsolete in favour of the term mid!fan as de_ned by Normark\ 0880[

1 The term {lobe| is used here in the context of the original de_nition of Mutti "0868# to denote unchannelised fan related deposits[

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divisible into four elements comprising "a# a slope valley system or subdued shelf!slope break cut by gullies or failure zones\ "b# a proximal ramp with feeder channels ~anked by mud!rich levees\ "c# a medial ramp dominated by channel levees and "d# an outer or distal ramp with depositional lobes[ The seismic character of the system is similar to that of mixed sand!mud fans[ Ramps are distinguished because the seismic envelope forms a belt of channel levees along the margins of the basin each feeding mid! fan lobes[ The lobes are often the only seismically resolv! able part of the fan\ forming discontinuous\ parallel to hummocky or mounded seismic packages of variable internal re~ector character[ An ancient example of a mixed sand!mud ramp res! ervoir system is provided by Forties System of the Central North Sea "Wills\ 0880# and the early Cretaceous Ach! imov Formation of the West Siberian basin[ In the latter example\ linear belts of mixed load clastics occur along the base of slope[ Thickest sands are preferentially developed during periods of relative sea!level fall[ Res! ervoir quality is typically poor because of the mixed nat! ure of the sediment load[ This reduces the commercial potential of the play[ Reservoir e}ectiveness is often a major element of risk associated with such plays[ 1[1[3[ Mud!rich systems These have a sand ] shale ratio less than 29) "Fig[ 6#[ They are common in basins with mature drainage patterns\ large source areas and where rivers and deltas are dominated by _ne!grained suspended load[ Mud!rich systems are volumetrically the most important deep! water clastic systems in the world|s oceans today[ They form large scale\ widespread systems "49Ð2999 km radius] Bouma et al[\ 0874^ Reading and Richards\ 0883#[ Find! ing and developing reservoirs within these systems pro! vides a major challenge for explorationists along many of todays continental margins because reservoir quality sands are con_ned to speci_c parts of the system[ 1[1[3[0[ Mud!rich slope aprons[ These are dominated by sediment derived from failure and:or partial detachment of muddy shelf and upper slope sediment "Fig[ 6a#[ The apron is dominated by slumps\ slides and mud!dominated debris wedges[ The slope margin is commonly char! acterized by erosional gullies and extensional rotational slumps generated by sediment failure and foundering[ The base of slope and basin margin is dominated by silt and mud rich debris wedges\ debris ~ows and slides at varying scales[ The basin margin may also display com! pressional toe thrusts related to repeated ramping of slide bodies[ The context and seismic character is broadly similar to mixed sand!mud counterparts[ Mounded seismic pack! ages dominate[ These are characterized by hummocky to chaotic re~ector hyperbolae\ passing basinward into

692

discontinuous parallel re~ectors[ The dominance of slum! ping and sliding within mud!rich slope aprons limits res! ervoir potential[ Occasionally\ retrogressive slumping of an apron and slope system exhumes coarse!grained clastic substrates or provides a topography to pond sand!laden turbidity currents[ 1[1[3[1[ Mud!rich submarine!fans[ Mud!rich fans include high e.ciency\ large "up to 2999 km radius# delta!fed\ open ocean fans which dominate modern continental margins[ They include the Bengal\ Amazon\ Mississippi and Indus fans "Fig[ 6b#[ Sediment is typically derived from major\ high suspended load ~uvial and deltaic sys! tems "Curray and Moore\ 0863^ Damuth and Flood\ 0874^ Damuth et al[\ 0877^ Garrison et al[\ 0871^ Coleman et al[\ 0872^ O|Connell et al[\ 0874#[ Fans are often ori! ented axially within a basin\ even where the axis lies at an angle to the main direction of sediment supply[ Fans are subdivided into inner:upper\ mid and out! er:lower fan elements[ The inner:upper fan has a broad head which grades imperceptibly into the continental slope[ It is dominated by slump blocks\ gullies\ troughs of varying scale and size\ together with a single\ large scale channel!levee system which issues from a large submarine canyon upslope[ The middle fan area is characterized by generally sinu! ous complexes of aggradational leveed channels built above the fan surface[ These diminish in size onto the lower middle fan and pass into unleveed shallow channels and constructional lobes "Nelson et al[\ 0868^ O|Connell et al[\ 0874^ Damuth et al[\ 0877#[ These unleveed chan! nels and lobes pass downdip into the outer:lower fan[ Modern mud!rich fans have been the subject of detailed investigation using high resolution\ single and multi!channel seismic "e[g[\ Bouma et al[\ 0874^ Kolla and Coumes\ 0876^ Mchargue and Webb\ 0875^ Damuth et al[\ 0877^ Manley and Flood\ 0877^ Weimer\ 0889#[ They are generally readily distinguished in the subsurface by their large scale and development of extensive channel! levee systems[ Seismically\ the inner fan is dominated by chaotic and mounded re~ector packages produced by slope failure and slumping[ The channel!levee systems show a charac! teristic {gull wing| seismic geometry oriented per! pendicular to the channel axis[ Individual levees are dominated by down!lapping\ low angle inclined re~ectors which thin and dip outwards from the channel core^ the core is dominated by strong discontinuous high!ampli! tude re~ections "HARs# with transparent zones[ The mid! fan displays smaller scale\ gull wing geometries of more limited relief^ these are also produced by channel levees[ In high resolution seismic data "2[4 khz# the lower:outer fan shows prolonged echoes with no penetration "Damuth\ 0879#[ Air gun single "099 Hz# and multi!chan! nel seismic data from the lower fan are dominated by discontinuous\ parallel to subparallel re~ections

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"Damuth\ 0879^ Droz\ 0872^ O|Connell et al[\ 0874^ Damuth et al[\ 0877#[ Despite being dominated by _ne!grained clastics\ mud! rich fans contain a range of potential but generally subtle exploration targets[ These include stacked reservoir sands in abandoned channel!_lls[ Thin bedded sands within the levee margin and more laterally extensive sands within lower fan lobes are also possible exploration targets "Weimer\ 0889#[ 1[1[3[2[ Mud!rich submarine ramps[ These are poorly documented in Recent[ Ancient examples are developed where sediment is supplied either directly or indirectly from suspended!load dominated shelf edge deltas[ Long! shore drift\ topset deltaic distributaries or active gullied channels at the shelf!slope break are other possible supply routes "Fig[ 6c^ Pickering\ 0872^ Woodrow and Isley\ 0872#[ The external character of these systems is broadly similar to their mixed sand!mud counterparts and shows four elements^ a subdued slope system\ proximal\ medial and distal ramp segments[ Channel!levees dominate the depositional record of these systems forming wedged shaped seismic packages with internal downlapping re~ectors[ Terminal lobes form the downdip equivalents of channel!levees\ but are more irresolvable on seismic[ 2[ Approaches to stratigraphic prediction Successful prediction of submarine!fan reservoirs is dependent upon three key factors[ Firstly\ an awareness of their variability and the signi_cant di}erences which can occur in sand distribution\ reservoir architecture and trapping geometries[ At the broad scale this is predictable and systematic in character[ Understanding the range and potential variability is facilitated by combining the fan classi_cation scheme with an appreciation of the fun! damental controls operating within a systems tract[ Secondly\ integration of core\ seismic architecture\ acoustic expression\ seismic facies and wireline log character facilitates assessment of the range of depo! sitional attributes within di}erent systems[ Thirdly\ sub! marine!fans are deep!marine {geological dustbins|[ That their lithological character is linked fundamentally to source area variability and composition is often forgotten or disregarded in exploration and appraisal[ The tools and techniques available for exploration and exploitation of submarine!fans fall into two broad groups[ Firstly\ there are remote techniques in which an understanding of the fan is built from a knowledge of the regional geology\ nature of the basin margin to hinterland characteristics\ palaeoclimate\ tectonic setting and sea! level changes[ This includes assessment of basin margin depositional systems\ the mechanism of sediment delivery to the basin and its a}ect on sand distribution and res!

ervoir architecture[ Such techniques are most commonly employed in the basin screening phase of exploration[ Secondly\ there are direct techniques where information from the fan is used to assess geological and geophysical characteristics to deduce sand distribution and reservoir architecture[ This approach becomes increasingly rel! evant as discoveries are appraised and developed[ We propose a three!stage approach to exploration and exploitation based largely on the analysis of seismic and wireline log data which are calibrated with core wherever possible[ , Basin screenin`] focuses on the potential range of fan plays within a basin\ before embarking on detailed stratigraphic analysis of individual elements of the basin _ll[ , Submarine!fan delineation] where potential fan plays and play fairways are identi_ed and delineated through detailed mapping leading to prospect evaluation[ , Submarine!fan characterization] here the internal characteristics of a fan system are assessed to reduce risk on reservoir presence and distribution during appraisal and production[ This systematic approach provides rigour and organ! ization to subsurface data collection\ collation\ synthesis and evaluation[ It is also applicable to evaluation of other reservoir types[ The ultimate objective of the three stages is to develop an understanding of reservoir architecture\ net to gross variation and distribution\ together with an appreciation of the range of uncertainties contained in the interpret! ations[ Given the possible range in reservoir architectures and net to gross distribution associated with di}erent fan classes\ it is important that all the available data are used throughout the three stages[ Even during charac! terization\ basin screening techniques will continue to be used in the search for new and often increasingly subtle targets within a play fairway[ 2[0[ Basin screening This relies on regional and basin scale tectono!strati! graphic analysis to de_ne the areal and temporal dis! tribution of depositional systems tracts at the basin margin\ and their relationship to depositional products within the basin[ This enables de_nition of areas of poss! ible fan development\ their likely reservoir facies and prospectivity[ The evaluation should focus on a number of key areas "Fig[ 7#] , The type of sediment supplied to the basin , Possible basin margin entry points , The mode of basinward sediment transport , The shape\ size and topography of the receiving basin[ Understanding such factors and considering them within the context of the fan classi_cation will help ident!

M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606 694

Fig[ 7[ Three!stage process for the evaluation of deep marine clastic systems involving remote and direct techniques] "a# basic screening to determine the likely nature and type of sediment supply\ potential entry points into the basin and the likely location of sediment deposition based on basin topography and geometry^ "b# system delineation in which a variety of seismic\ sequence stratigraphic and depositional analyses are used to de_ne the extent of the system^ "c# system characterization in which data from core and wireline log data are used with calibrated seismic architecture and geophysical modeling to de_ne the character of the system[

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M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606

ify the most likely areas and stratigraphic sections for fan development[ The classi_cation facilitates the assessment and description of di}erent options for a given play[ It particularly helps to distinguish non!prospective fan types[ Emphasis should be on maintaining awareness of the range of potential models and the key uncertainties associated with each\ rather than attempting to de_ne a single solution[ Appreciating this variability leads to a clearer assessment of exploration risk[ 2[0[0[ Nature of sediment supply to the basin Understanding hinterland characteristics using the regional geology of surrounding areas often gives an important clue to the type of sediment available to the basin[ The sediment type has a fundamental impact on the type of deep!marine clastic systems developed[ For example\ the early Tertiary history and prospectivity of the North Sea basin is largely controlled by hinterland geology "Bowman\ 0874#[ Rejuvenation of the Scottish Highlands and Shetland Platform caused by the early opening of the North Atlantic led to the liberation of large volumes of coarse clastics into the U[K[ Central and Northern North Sea and the Western Atlantic Margin[ In contrast\ the contemporaneous uplift of the pre! dominantly schistose Norwegian mainland contributed mainly muddy sediment to the Norwegian North Sea Basin[ This explains the poor Tertiary prospectivity over much of the Norwegian sector of the North Sea[ Techniques such as gravity and magnetic surveys and subcrop maps provide useful indicators of the hinterland[ Seismic facies analysis of basin!margin sequences helps de_ne potential areas of sand accumulation "Sangree and Widmier\ 0866#[ The seismic architecture of the basin margin can be used to de_ne broad scale depositional systems and locate sites of coarse clastic deposition[ Inte! gration of these data with wireline log and core infor! mation from basin margin wells provides information on the characteristics of potential sediment source areas[ These data enable constraints to be placed upon the sedi! ment fed to a fan which is important for predicting fan type "Fig[ 8#[ 2[0[1[ De_ning basin margin entry points Entry points and associated feeder systems to the basin are only rarely imaged on seismic[ More often\ the interpreter relies upon understanding basin margin drain! age patterns and their impact on the location of sub! marine!fan depocentres "Fig[ 09#[ Active or relict structural lineaments often exert a fun! damental in~uence on the site of sediment input to a basin in both extensional and compressional regimes[ Transfer faults\ typical of dip!slip and strike slip exten! sional settings\ generally form physiographic lows which commonly act as corridors for basinward transport sedi! ment[ Within compressional margins\ lateral ramps may

provide similar conduits for the input of coarser grained clastics to the basin[ Delineating relict or active structural grain\ combined with interval isopach maps provides important clues to the controls on sediment distribution patterns and the location of sediment entry sites along a basin margin[ This is amply demonstrated in the North Sea\ where the sites of most early Tertiary submarine!fans can be linked with topographic lows related to the underlying Jurassic rift topography "Bowman\ 0874#[ Isopach mapping\ com! bined with backstripping "preferably 2D# and basin modeling are also valuable for de_ning pre!depositional topography of a basin margin and also the basin axis[ An excellent example of this approach is provided by Wood and Hall "0882#\ from the Late Jurassic submarine!fans in the Brae trend of the North Sea\ South Viking Graben[ 2[0[3[ Mechanism of sediment transport to the basin This controls the type and degree of facies organization within a fan\ which in turn a}ects reservoir geometry and architecture "Fig[ 00#[ Local in!situ reworking and failure of a slope "passive sediment supply# typically leads to disorganized fans of poor reservoir quality at best[ Exam! ples of such systems include submarine talus cones\ slope aprons\ submarine slides and slumps[ Input of sediment directly from canyon or channel systems "active supply# leads to more prospective\ organized systems with more predictable and better reservoir quality "Fig[ 2#[ This is particularly true where sediment has been reworked by shelfal processes[ In actively!fed systems it is important to distinguish between submarine!fans supplied directly from coeval deltaic and shelf systems\ and those derived from the erosion of older basin margin sediment or rock[ Depo! sitional products associated with di}erent supply mech! anisms can be distinguished by assessing the volume of sediment supplied to the fan and its mineralogy[ The assessment is further helped by considering the sequence stratigraphic and depositional systems tract context of the fan[ There are a variety of other tools which help to under! stand the supply mechanism to a basin[ Biofacies together with faunal:~oral abundances can broadly distinguish periods of sediment by!pass and reworking from episodes of coeval basin!margin deposition "Vail and Wornardt\ 0889#[ Seismic stratigraphy "sensu lato# and chrono! stratigraphy are used to constrain lithology and time relationships between basin margin and basin axis depo! sitional packages[ Seismic facies analysis helps dis! tinguish systems fed by slumps and slides from those linked to major shelf incisions[ Core and petrographic studies are used to determine depositional processes and assess the mechanisms of sediment transport to the basin[ It is di.cult to distinguish between small!scale fans fed by passive and active feeder systems^ this leads to additional uncertainty in any reservoir model and play[

M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606 696

Fig[ 8[ Basin screening I] key data sets used in the stratigraphic prediction of submarine fan systems from an understanding of the type of sediment supplied to the basin[ The calibre of sediment available to the basin may be inferred from subcrop mapping and seismic facies analysis as well as interpretations of lithological character from wireline logs and core[ From these data an initial assessment can be made of the likely lithological character of the system "e[g[\ sand rich\ mud!rich# and the potential pitfalls and plays within the basin[

697 M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606 Fig[ 09[ Basin screening II] key data sets used in the stratigraphic prediction of submarine fans systems using an understanding of the location and character of basin mar`in entry points and their distribution[ A variety of techniques can be used to determine entry point distribution varying from simple drainage and structure maps of time equivalent shelf and deltaic systems to the characterization of basin margins systems through seismic facies and seismic sequence mapping[ Back!stripping may provide a further tool for reconstructing basin margin geometry and structure as an aid in de_ning likely entry points[ From these data an initial assessment can be made of the frequency and distribution of entry points to the basin "e[g[\ single vs multiple point source#[

M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606 698

Fig[ 00[ Basin screening III] key data sets used in the stratigraphic prediction of submarine fans systems using an understanding of the mechanism of sediment supply[ Inferences on sediment supply mechanism can be made from biofacies and faunal abundance peaks\ as well as seismic sequence and facies analysis which de_ne the relationships between shelf and basin systems as well as their degree of internal organization[ These data when calibrated to core information may provide useful tools in distinguishing the temporal relationships between shelf and basin systems\ as well as the degree to which sediment supply may have occurred as a result of direct and coeval sediment in~ux or major periods of erosion and bypass[

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During basin screening it is essential to remember all potential pitfalls and alternative interpretations for mounded seismic packages within basin settings[ 2[0[4[ De_ning basin geometry and topography The shape and topography of a basin exert a signi_cant control on depositional processes and sites together with the form and architecture of any fan system "Fig[ 01#[ Symmetrical radial fan systems are the exception rather than the rule[ However\ whilst overall fan form remains variable\ the main building blocks "architectural elements# of the system "lobes\ channels\ etc[# remain essentially the same[ The shape and topographic charac! teristics of a basin will\ however\ a}ect the stacking pat! tern and organization of individual architectural elements[ In unconstrained\ low!relief basin plains\ mud!rich high e.ciency fans can transport signi_cant volumes of sediment across large distances " × 099 kms# from the source area\ to form large!scale elongate fans[ In contrast\ low e.ciency systems dominated by sand!rich high!den! sity turbidity currents\ are less likely to transport large volumes of detritus over signi_cant distances without the aid of relatively high slopes or ~ow con_nement to sustain the momentum of the ~ow[ Hence\ sand!rich and gravel! rich systems commonly develop close to the base of a submarine slope "Fig[ 1#[ In actively structured slopes\ sea ~oor topography pro! foundly a}ects the distribution pattern of turbidite deposits by] "a# focusing ~ows and sediment transport pathways "b# impeding sediment transport to the basin through the development of structural barriers and the for! mation of intraslope basins "c# changing the ~ow characteristics of turbidity currents "e[g[\ ~ow stripping#\ resulting in localized coarse clas! tic deposits which are di.cult to predict[ Simple relationships between transport e.ciency and sediment calibre may not apply in those basins where the basin ~oor is structured beyond the submarine slope[ In such cases\ sea ~oor topography may impede the trans! port of both coarse! and _ne!grained clastics[ This can result in either enforced aggradation of mud!rich systems close to the base of slope or the delivery of sand!rich high!density turbidity currents further into a basin than is the norm[ Determining the shape and form of the receiving basin relies upon regional drainage\ bathymetry and ortho! contour maps for predicting possible transport routes and depositional sites for turbidity currents initiated at any point along the basin margin[ Linking these data with an understanding of the location and lithological character of relict and:or active depositional systems at the basin margin\ will constrain risk and reduce uncer! tainty in de_ning and locating submarine!fan reservoirs[

2[1[ System delineation This phase of analysis focuses upon the mapping and delineation of a system using techniques which enhance data imaging and provide detailed insight into its depo! sitional context and character "Fig[ 02#[ It is also impor! tant to understand the context of the fan and the scale of the system to identify interpretation pitfalls and for prediction of internal architecture[ 2[1[0[ De_ning and imaging the system In seismic data\ submarine!fans are commonly imaged as subtle mounded packages[ However\ as discussed earl! ier\ such mounded geometries can represent a wide spec! trum of deep!marine clastic systems including slumps\ slides and contourite mounds[ Seismic redisplay2 tech! niques are particularly useful for enhancing the external geometry and internal acoustic character to help interpretation and de_nition of reservoir distribution and type[ 2[1[1[ Depositional context and signi_cance of mounds The location and depositional setting of a fan provide important clues to its organization\ sand distribution and reservoir architecture[ Relating the location of mounds to the gradient and topography of a depositional slope and basin margin helps distinguish between prospective\ organized fan systems and more disorganized systems which carry higher risk on reservoir presence and e}ec! tiveness[ Organized submarine!fan systems are more likely to be con_ned to larger scale intraslope depressions or topo! graphic lows within a basin[ Mounding within a sub! marine slope setting or on any minor depositional slope is more likely to be produced by disorganized systems such as submarine slides and slumps[ For mounded seis! mic packages in basinal settings the site of sand depo! sition is largely controlled by the e.ciency of the submarine!fan "Fig[ 1#[ In more e.cient mixed sand!mud and mud!rich systems the main site of sand deposition will be at a distance from the base of the slope[ 2[1[2[ Scale of the depositional system The scale of the depositional system may constrain the architecture and net!to!gross characteristics of a fan[ In general\ the larger the areal extent and scale of a fan\

2

The term {redisplay| is used here to denote the presentation of post! stack seismic data to enhance internal acoustic character[ The process may involve "a# the simple manipulation of data to produce colour\ squashed or enlarged formats or "b# the representation of complex seismic attributes where the seismic signal is resolved into its amplitude\ frequency and phase components[ The term {redisplay| is commonly confused with seismic processing "sensu stricto# in which raw data undergoes a number of mathematical transformations prior to migration and display[

M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606 Fig[ 01[ Basin screening IV] key data sets used in the stratigraphic prediction of submarine fans systems using an understanding of `eometry and topo`raphy of the receivin` basin[ The site of coarse clastic deposition is strongly controlled by basin shape and topography[ Regional drainage patterns of basin combined with orthocontour mapping provide tools for mapping sediment transport pathways whilst structural trends and isopach maps provide an understanding of the likely topography of the basin and the potential for trapping deep water clastics in localized depocentres[

600

601 M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606 Fig[ 02[ System delineation] a variety of techniques can be used to de_ne and delineate the extent of the fan system[ These include the use of seismic redisplay techniques that enhance the internal character of the seismic envelope and its acoustic facies\ to more conventional analyses in which the likely provenance of the sediment from the basin margin is used in conjunction with the location and scale of basin margin sequences to predict system type[

M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606 602

Fig[ 03[ System characterization] the _nal stage of analysis attempts to use available data from the system itself to predict internal character[ Seismic facies mapping of the seismic envelope may be used to determine the degree of internal organization of the system\ whilst seismic modeling provides a mechanism to test di}erent interpretations of internal heterogeneity by comparing observed acoustic character with modeled seismic response[ Parallel facies and wireline log analyses provide independent calibration to likely depositional and reservoir architectural models based solely on seismic[

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M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606

the lower the net to gross of the system "Reading and Richards\ 0883#[ This is not solely due to sediment trans! port e.ciency[ Mud!rich systems do not support high gradients across the fan surface and\ therefore\ deposits tend to be built laterally rather than vertically[ There is also an increased probability of reaching a large scale\ mud!rich\ drainage and source area[ Sand!rich systems are generally small\ thin "099 m median thickness# and di.cult to resolve on regional seismic data "Reading and Richards\ 0883#[ Examples of thicker " × 099 m# sand!rich turbidite successions often represent fan complexes rather than single fan systems "e[g[\ North Sea Tertiary#[ In contrast\ mud!rich systems can form thick successions\ which are readily dis! tinguished on regional seismic lines[ 2[2[ System description and characterization The _nal stage of any evaluation focuses on de_ning sand distribution and the detailed reservoir architecture[ This relies upon analysis of the internal geological and geophysical attributes of a fan using seismic\ wireline log and core data[ These are compared and calibrated with analogues from both outcrops and working plays[ The analysis aims to] "a# develop qualitative and quantitative estimates of the range of sand distribution "b# evaluate net!to!gross character "c# de_ne the form and spatial distribution of archi! tectural elements "d# de_ne optimum drilling locations "Fig[ 03#[ Semi!quantitative assessment of the range of net to gross within a target relies upon a number of obser! vational and analytical modeling techniques[ It is clear from previous discussions that seismic geometry and internal acoustic character "seismic facies# of a fan pro! vide an indication of its fundamental building blocks and hence overall fan type[ These concepts can be tested by modeling the seismic response of a system using inter! preted architectural geometries and a range of net to gross distributions[ The process uses standard or calibrated velocity and density information to develop an acoustic impedance model[ In parallel with such geophysical approaches\ sig! ni_cant information on the depositional facies and facies associations of the fan system can be derived from inte! gration of core and log information to infer details of fan type and net to gross distribution[ Dipmeters\ although of limited use in palaeocurrent analysis of turbidite systems\ can provide an important means of distinguishing between organized and disorganized facies by assessment of the consistency\ quality and direction of measured dips throughout zones of interest[ Finally\ the value of outcrop analogues should not be underestimated[ Selec! tion of suitable and appropriate analogues can be di.cult

and time consuming[ They can also provide invaluable information on the dimension\ form and relationships of di}erent architectural elements within a system[ 3[ Conclusions This paper attempts to illustrate the variability of sub! marine!fan and other deep!water clastic systems and dis! cusses the range of tools and techniques available in the exploration\ appraisal and development for such reser! voirs[ Accurate prediction of reservoir presence\ geometry and trap integrity will not come from appli! cation of a single interpretative model[ It must be based upon an integrated approach[ Conclusions rely on sys! tematic observation and a clear understanding of the link between the controls of fan systems and the resulting depositional products and their expression in geological and geophysical data "Fig[ 7#[ Interpretations must be constantly reassessed with the receipt of new data and insights to gain a clearer under! standing of the risk and uncertainty associated with the exploration and development of submarine!fan reservoir systems[ Without this\ potential pitfalls will be over! looked and geological interpretations of the distribution of reservoir and non!reservoir elements oversimpli_ed[ This leads\ in turn\ to an underestimate of the risk associ! ated with reservoir presence and trapping geometry[ Greater pragmatism together with a better under! standing of the link between controls\ processes and depositional products will ultimately increase our ability and accuracy in the exploration and stratigraphic pre! diction of reservoirs of deep!water clastic origin[ This should always be combined with a healthy awareness of the need to constantly question and modify any models[ Acknowledgements The work presented in this summarises a signi_cant volume of research by the authors over the last 09 years as part of BP internal and externally funded studies[ By necessity\ the paper represents a summary of exhaustive analyses carried out by the authors and Geoscientists within BP Exploration evaluating deep!marine clastic res! ervoir and play systems[ Richards and Bowman wish to thank BP Exploration for permission to publish the paper and to various colleagues at BP who have contributed over many years to the ideas presented in this paper[ Thanks are extended to colleagues at BP for their con! structive reviews of earlier drafts of the manuscript[ The authors are also grateful to Jed Damuth and an anony! mous reviewer for providing helpful suggestions for improving the manuscript for publication[ References Alexander\ R[ W[ S[\ Scho_eld\ K[\ + Williams\ M[ "0880#[ Under! standing the Forth _eld reservoir\ block 8:12b^ myths of deep sea

M[ Richards et al[:Marine and Petroleum Geolo`y 04 "0887# 578Ð606 sands exploded[ EAPG\ 2rd Conference\ Florence\ Italy] Tech[ Pro! gramme and Abstracts[ European Association of Petroleum Geo! scientists\ Zeist[ Belderson\ H[ H[\ Kenyon\ N[ H[\ Stride\ A[ H[\ + Pelton\ C[ D[ "0873#[ A {braided| distributary system on the Orinoco deep sea!fan[ Mar[ Geol[\ 45\ 084Ð195[ Boote\ D[ R[ D[\ + Gustav\ S[ H[ "0876#[ Evolving depositional systems within an active rift\ Witch Ground Graben\ North Sea[ In J[ Brooks and K[ W[ Glennie\ "eds[#\ Petroleum Geolo`y of North West Europe "pp[ 708Ð723#[ London] Graham and Trotman[ Bouma\ A[ H[\ Normark\ W[ R[\ + Barnes\ N[ E[ "0874#[ Submarine Fans and Related Turbidite Systems[ Springer Verlag[ Bowman\ M[ B[ J[ "0874#[ Cenozoic[ In E[ K[ W[ Glennie et al[\ Intro! duction to the Petroleum Geolo`y of the North Sea[ JAPEC\ Sup! plementary Course Notes No[ 015[ 47[ Brooks\ J[\ + Glennie\ K[\ "Eds[# "0874#[ Petroleum Geolo`y of North! West Europe[ London] Graham and Trotman[ Busby!Spera\ C[ "0874#[ A Sand!rich submarine fan in the Lower Meso! zoic Mineral King Caldera Complex\ Sierra Nevada\ California[ J[ Sedim[ Petrol[ 44\ 265Ð280[ Case\ J[ E[ "0863#[ Major basins along the continental margin of north! ern South America[ In C[ A[ Burke + C[ L[ Drake "Eds[#[ The Geolo`y of Continental Mar`ins "pp[ 622Ð630#[ New York] Springer Verlag[ Chann\ M[ A[\ + Dott\ R[ H[ Jr[ "0872#[ Shelf and Deep Sea Sedi! mentation in Eocene Forearc Basin\ Western Oregon*Fan or Non! Fan< Bull[ Amer[ Assoc[ Petrol[ Geol[ 56\ 1099Ð1005[ Coleman\ J[ M[\ Prior\ D[ B[\ + Lindsay\ J[ F[ "0872#[ Deltaic in~uences on shelf!edge instability processes[ In D[ J[ Stanley + G[ T[ Moore "Eds[#[ The shelf!break^ critical interface on continental mar`ins[ Soc[ Econ[ Paleon[ + Mineralo`[ Spec[ Publ[\ 22 "pp[ 010Ð026#[ Collela\ A[\ + Prior\ D[ B[ "Eds[# "0889#[ Coarse!grained deltas] Inter! national Association of Sedimentolo`ists Special Publication\ 09\ 246[ Colmenero\ J[ R[\ Agueda\ J[ A[\ Fernandex\ L[ P[\ Salvador\ C[ I[\ Bahamonde\ J[ R[\ + Barba\ P[ "0877#[ Fan!delta systems related to the Carboniferous evolution of the Cantabrian Zone\ northwestern Spain[ In W[ Nemec + R[ J[ Steel\ "Eds[#\ Fan Deltas] Sedimentolo`y and Tectonic Settin`s[ Glasgow] Blackie\ "pp[ 156Ð174#[ Curray\ J[ R[\ + Moore\ D[ G[ "0863#[ Sedimentology and tectonic processes in the Bengal Deep!Sea Fan and Geosyncline[ In G[ A[ Burk + C[ K[ Drake "Eds[#\ Geolo`y of Continental Mar`ins\ "pp[ 506Ð516#[ New York] Springer Verlag[ Damuth\ J[ E[ "0879#[ Use of high frequency "2[4Ð01 kHz# echograms in the study of bottom sedimentation processes in the deep sea] a review[ Marine[ Geol[ 27\ 40Ð64[ Damuth\ J[ E[\ + Flood\ R[ D[ "0874#[ Amazon Fan\ Atlantic Ocean[ In Arnold H[ Bouma\ William R[ Normark + Neal E[ Barnes "Eds[#\ Submarine Fans and Related Turbidite Systems[ "pp[ 86Ð095#[ New York\ Berlin\ Heidelberg\ Tokyo] Springer Verlag[ Damuth\ J[ E[\ Flood\ R[ D[\ Kowsmann\ R[ O[\ Belderson\ R[ H[\ + Gorini\ M[ A[ "0877#[ Anatomy and growth pattern of Amazon Deep!Sea fan as revealed by long!range side!scan sonar "Gloria# and high resolution seismic studies[ Am[ Assoc[ Petrol[ Geol[ 61\ 774Ð800[ De|Ath\ N[ G[\ + Schuyleman\ S[ F[ "0870#[ The Geology of Magnus Oil_eld[ In L[ V[ Illing + G[ D[ Hobson "Eds[#\ Petroleum Geolo`y of the Continental Shelf of North!West Europe "pp[ 231Ð240#[ London] Heyden[ Droz\ L[ "0872#[ L|eventail sous marin profond du Rhone "Golfe de Lion#] `rand traits morpholo`ues et structure semi!profonde[ Paris] These 2e Cycle[ Droz\ L[\ + Bellaiche\ G[ "0874# Rhone Deep Sea Fan] Morphostructure and growth pattern[ Bull[ Am[ Assoc[ Petrol[ Geol[ 58\ 359Ð368[ Ferrentinos\ G[ G[\ Papatheodorou\ G[\ + Collins\ M[ B[ "0877#[ Sub! marine transport processes on an active submarine fault scarp] Gulf of Corinth\ Greece[ Mar[ Geol[ 72\ 32Ð50[ Field\ M[ E[\ + Clark\ S[ H[ Jr "0868#[ Small scale slumps and their

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signi_cance for basin slope processes\ southern California border! land[ In L[ T[ Doyle + O[ H[ Pilkey Jr "Eds[#\ Geolo`y of Continental Slopes "pp[ 112Ð129#[ Soc[ Econ[ Paleon[ Mineral[ Spec Publ\ 16[ Galloway\ W[ E[ "0864#[ Process framework for describing the mor! phologic and stratigraphic evolution of deltaic depositional systems[ In M[ L[ Broussard "Ed[#\ Deltas\ Models for Exploration "pp[ 76Ð 87#[ Houston] Houston Geological Society\ 5[1[5[2[5[3\ Fig[ 5\3\01[3[2[ Garland\ C[ R[ "0882#[ Miller Field] Reservoir stratigraphy and its impact on development[ In J[ R[ Parker "Ed[#\ Petroleum Geolo`y of Northwest Europe] Proceedin`s of the 3th Con`ress "pp[ 390Ð303#[ The Geological Society of London[ Garrison\ L[ E[\ Kenyon\ N[ H[\ + Bouma\ A[ H[ "0871#[ Channel systems and lobe construction in the Mississippi Fan[ Geo!Marine Letters\ 1\ 20Ð28[ Glennie\ K[ W[ "Ed[# "0873#[ Introduction to the Petroleum Geology of the North Sea[ Blackwell Scienti_c Publications 125 pp[ Haner\ B[ E[ "0860#[ Morphology and sediments of Redondo submarine fan southern California[ Bull[ Geol[ Soc[ Am[ 71\ 1302Ð1321[ Heller\ P[ L[\ + Dickinson\ W[ R[ "0874#[ Submarine Ramp Facies Model for Delta!Fed Sand!Rich Turbidite Systems[ Am Assoc[ Petrol[ Geol[ 58\ 859Ð865[ Heritier\ F[ E[\ Lossel\ P[\ + Wathne\ E[ "0868#[ Frigg Field*large submarine fan trap in Lower Eocene rocks of North Sea Viking Graben[ AAPG Bulletin 52\ 0888Ð1919[ Illing\ L[ V[\ + Hobson\ D[ G[ "0870#[ The Petroleum Geolo`y of the Continental Shelf of N[ W[ Europe[ Hayden[ Kleverlaan\ K[ "0878#[ Three distinctive feed!lobe systems within one time slide of the Tortonian Tabernas fan\ S[ E[ Spain[ Sedimentolo`y 25\ 14Ð35[ Kolla\ V[\ + Coumes\ F[ "0876#[ Morphology\ internal structure and seismic stratigraphy and sedimentation of the Indus Fan[ Bull[ Am[ Assoc[ Petrol[ Geol[ 57\ 205Ð221[ Link\ M[ H[\ + Nilsen\ T[ H[ "0879#[ The Rocks Sandstone\ An Eocene Sand!Rich Deep Sea Fan Deposit\ Northern Santa Lucia Range\ California[ J[ Sedim[ Petrol[ 49\ 472Ð591[ Link\ M[ H[\ + Welton\ J[ E[ "0871#[ Sedimentology and reservoir potential of Matilija Sandstone] an Eocene sand!rich deep sea fan and shallow marine complex\ California[ Bull[ Am[ Assoc[ Geol[ 55\ 0403Ð0423[ Lowe\ D[ R[ "0871#[ Sediment Gravity Flows II] Depositional Models with Special Reference to the Deposits of High Density Turbidity Currents[ J[ Sedim[ Petrol[ 41\ 168Ð186[ Manley\ P[ L[\ + Flood\ R[ D[ "0877#[ Cyclic sediment deposition within the Amazon Deep!Sea fan[ Am[ Assoc[ Petrol[ Geol[ 61\ 801Ð814[ McGovney\ J[ E[\ + Radovich\ B[ J[ "0874#[ Seismic stratigraphy of the Frigg Fan Complex[ In O[ R[ Berg + D[ G[ Wolverton "Eds[#\ Seismic Strati`raphy II An Inte`rated Approach "pp[ 028Ð045#[ Am[ Assoc[ Petrol[ Geol[ Mem 28[ Mchargue\ T[\ + Webb\ J[ E[ "0875#[ Internal geometry\ seismic facies and petroleum potential of canyons and inner fan channels of the Indus submarine fan[ Am[ Asoc[ Petrol[ Geol[ 69\ 050Ð079[ Mutti\ E[ "0868#[ Turbidities et cones sous!margins profonds[ In P[ Homewood "Ed[#\ Sedimentation Detritique "Fluviatile\ littorale et Marine# "pp[ 242Ð308#[ Inst[ Geol[ Universite de Fribourg\ Fribourg[ Mutti\ E[ "0874#[ Turbidite systems and their relations to depositional sequences[ In G[ G[ Zu}a "Ed[#\ Provenance of Arenites\ NATO! ASI Series "pp[ 54Ð82#[ Reidal Publishing Company[ Mutti\ E[\ + Johns\ D[ R[ "0867#[ The role of sedimentary bypassing in the genesis of fan fringe and basin plain turbidities in the Hecho Group system "south!central Pyrenees#[ Memorie Societa Geolo`ica Italiana 07\ 04Ð11[ Mutti\ E[\ + Ricci Lucchi\ F[ "0864#[ Turbidite facies and facies associ! ations[ Field Trip Guidebook A!00[ 8th Int[ Sedimentolo`y Con`r[ Nice\ France "pp[ 10Ð25#[ 01[21\ 01[3[2[ Mutti\ E[\ + Normark\ W[ R[ "0876#[ Comparing Examples of Modern

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and Ancient Turbidite Systems] Problems and concepts[ In J[ K[ Leggett + G[ G[ Zu}a "Eds[#\ Marine Clastic Sedimentolo`y "pp[ 0Ð 27#[ London] Graham and Trotman[ Nardin\ T[ R[\ Hein\ F[ J[\ Gorsline\ D[ S[\ + Edwards\ B[ D[ "0868#[ A review of mass movement processes\ sediment and acoustical characteristics and contrasts in slope and base of slope systems versus canyon fed basin ~oor systems[ In L[ J[ Doyle\ + O[ H[ Pilkey "Eds[#\ Geolo`y of Continental Slopes "pp[ 50Ð62#[ Soc[ Econ[ Paleon[ Mineral Spec[ Publ[ 16[ Nelson\ "0872#[ Nelson\ H[ C[\ + Nilsen\ T[ "0873#[ Modern and ancient deep sea fan sedimentation[ Soc[ Econ[ Palaeon[ Mineral[ Short Course 03[ Nelson\ H[ C[\ Maldonado\ A[\ Coumes\ F[\ Got[ H[\ + Monaco\ A[ "0874#[ Ebro Fan\ Mediterranean[ In Arnold H[ Bouma\ William R[ Normark\ + Neil E[ Barnes "Eds[#\ Submarine Fans and Related Turbidite Systems "pp[ 010Ð017#[ New York\ Berlin\ Heidelberg\ Tokyo] Springer!Verlag[ Nelson\ H[ C[\ + Maldonado\ A[ "0877#[ Factors controlling depo! sitional patterns of Ebro turbidite systems\ Mediterranean Sea[ Am[ Assoc[ Petrol[ Geol[ 61\ 587Ð605[ Nilson\ T[ H[ "0879#[ Modern and Ancient Submarine fans] discussion of papers by R[ G[ Walker + W[ G[ Normark[ Bull[ Am[ Ass[ Petrol[ Geol[ 53\ 0983Ð001[ Nilsen\ T[ H[ "0870#[ Early Cenozoic stratigraphy\ tectonics and sedi! mentation of the Central Diablo Range between Hollister and New Idria[ In V[ Frizzell et al[\ Geolo`y of the Central and Northern Diablo Ran`e\ California "pp[ 10Ð23#[ SEPM Paci_c Section Field trip guidebook[ Nilsen\ T[ H[\ Normark\ W[ R[\ + Walker\ R[ G[ "0879#[ Modern and ancient submarine fans] discussion of papers and reply[ AAPG Bulletin 53\ 0983Ð0001[ Normark\ W[ R[ "0869#[ Growth patterns of deep sea fans[ Bull[ Am[ Assoc[ Petrol[ Geol[ 43\ 1069Ð1084[ Normark\ W[ R[ "0863#[ Submarine canyons and fan valleys a}ecting growth patterns of deep sea fans[ In R[ H[ Dott Jr[ + Shaver "Eds[#\ Modern and ancient `eosynclinal sedimentation "pp[ 45Ð57#[ Soc[ Econ[ Paleon[ Mineral Spec[ Publ[ 08[ Normark\ W[ R[ "0867#[ Fan Valleys\ Channels + Depositional Lobes on Modern Submarine Fans] Characters for the recognition of Sandy Turbidite Environments[ Am[ Ass[ Petrol[ Geol[ 51\ 801Ð820[ Normark\ W[ R[ "0879#[ Modern and ancient submarine fans] reply[ Bull[ Am[ Ass[ Petrol[ Geol[ 53\ 0097Ð0001[ 01[3[2[ Normark\ W[ R[ "0880#[ Turbidite elements and the obsolescence of the suprafan concept[ Giornale di Geolo`ia Serie 2a\ 42\ n1\ 0Ð09[ Normark\ W[ R[\ Piper\ D[ J[ W[\ + Hess\ G[ R[ "0868#[ Distributary channels\ sand lobes and mesotopography of Navy Submarine Fan\ California Borderland\ with applications to ancient fan sediments[ Sedimentolo`y 15\ 638Ð663[ O|Connell\ S[\ Stelting\ C[ E[\ Bouma\ A[ H[\ Coleman\ J[ M[\ Cremer\ M[\ Droz\ L[\ Meyer!Wright\ A[ A[\ Normark\ W[ R[\ Pickering\ K[ T[\ Stow\ D[ A[ V[\ + DSDP Leg 85 Shipboard Scientists "0874#[ Drilling Results on the Lower Mississippi Fan[ In A[ H[ Bouma\ W[ R[ Normark\ + N[ E[ Barnes "Eds[#\ Submarine Fans and Related Turbidite Systems[ Frontiers in Sedimentary Geolo`y "pp[ 180Ð187#[ Springer!Verlag[ Orton\ G[ J[\ + Reading\ H[ G[ "0882#[ Variability of deltaic processes in terms of sediment supply\ with particular emphasis on grain size[ Sedimentolo`y 39\ 364Ð401[ Pickering\ K[ T[ "0872#[ Transitional submarine fan deposits from the late Precambrian Kongsfjord Formation Submarine Fan\ Finmark\ N[ Norway[ Sedimentolo`y 29\ 070Ð088[ Piper\ D[ J[ W[\ Kontopoulos\ N[\ Chronis\ G[\ + Panagos\ A[ G[ "0889#[ Modern fan deltas in the Western Gulf of Corinth\ Greece[ Geo!Marine Letters 09\ 40Ð01[ Prior\ D[ B[\ + Bornhold\ B[ D[ "0877#[ Submarine morphology and processes of fjord fan deltas and related high!gradient systems] modern examples from British Colombia[ In W[ Nemec + R[ J[

Steel "Eds[#\ Fan Deltas] Sedimentolo`y and Tectonic Settin`s "pp[ 014Ð032#[ Glasgow] Blackie[ Prior\ D[ B[\ + Bornhold\ B[ D[ "0889#[ The underwater development of Holocene fan deltas[ In A[ Collela and D[ B[ Prior "Eds[#\ Coarse! `rained deltas] International Association of Sedimentolo`ists Special Publication 09\ "pp[ 64Ð89#[ Reading\ H[ G[ "0880#[ The classi_cation of Deep!Sea depositional systems by sediment calibre and feeder system[ Journ[ Geol[ Soc[ London 037\ 316Ð329[ Reading\ H[ G[\ + Orton\ G[ J[ "0880#[ Sediment calibre] a control on facies models with special reference to deep sea depositional systems[ In D[ W[ Muller\ J[ A[ McKenzie\ + H[ Weissert "Eds[#\ Contro! versies in Modern Geolo`y "pp[ 74Ð000#[ Academic Press[ Reading\ H[ G[\ + Richards\ M[ T[ "0883#[ The classi_cation of deep! water siliciclastic depositional systems by grain size and feeder systems[ Am[ Assoc[ Petrol[ Geol[ 67\ 681Ð711[ Richards\ M[ T[\ + Bowman\ M[ B[ J[ "0887# "in press# Submarine Fan Systems II] Variability in Reservoir Architecture and Log Charac! ter[ Mar[ Petrol Geol[ Sangree\ J[ B[\ + Widmier\ J[ M[ "0866#[ Seismic interpretation of clastic depositional facies[ In Seismic Strati`raphy*Applications to Hydrocarbon Exploration American Association of Petroleum Geol! o`ist Memoir 15\ 054Ð073[ Sarg\ J[ R[\ + Skjold "0871#[ Stratigraphic Traps in Palaeocene Sands in the Balder Area\ North Sea[ In M[ T[ Halbouty "Ed[#\ The Deliberate Search for the Subtle Trap] Am[ Assoc[ Petrol[ Geol[ Mem[ 21 "pp[ 086Ð195#[ Stow\ D[ A[ V[ "0874#[ Deep Sea clastics] where are we and where are we going< In P[ J[ Brenchley + B[ P[ J[ Williams "Eds[#\ Sedimentolo`y] Recent Developments and applied aspects "pp[ 56Ð82#[ Geol[ Soc[ London[ Publ[ No[ 07 Oxford[ Blackwell Scienti_c Publications[ Stow\ D[ A[ V[ "0875#[ Chapter 01 Deep Clastic Sea[ In H[ G[ Reading "Ed[#\ Sedimentary Environments + Facies "pp[ 288Ð333#[ Blackwell Scienti_c Publications[ Surlyk\ F[ "0867#[ Submarine fan sedimentation along fault scarps on tilted fault blocks "Jurassic!Cretaceous boundary\ East Greenland#[ Bull[ Grnl[ Geol[ Under[ 017\ 097[ Surlyk\ F[ "0873#[ Fan!delta to submarine fan conglomerates of the Volgian!Valanginian Wollaston Foreland Group\ East Greenland[ In E[ J[ Koster + R[ J[ Steel "Eds[#\ Sedimentolo`y of Gravels and Con`lomerates "pp[ 248Ð271#[ Canadian Society of Petroleum Geol! ogists Memoir\ 09[ Surlyk\ F[ "0876#[ Slope and deep shelf gully sandstones\ Upper Jurassic\ East Greenland[ AAPG Bulletin 60\ 353Ð364[ Surlyk\ F[ "0878#[ Mid!Mesozoic syn!rift turbidite systems\ controls and predictions[ In J[ D[ Collinson "Ed[#\ Correlation in Hydrocarbon Exploration "pp[ 120Ð130#[ Norwegian Petroleum Society[ London] Graham and Trotman[ Turner\ C[ C[\ Cohen\ J[ M[\ Connell\ E[ R[\ + Cooper\ D[ M[ "0876#[ A depositional model for the South Brae oil_eld[ In J[ Brooks + K[ Glennie "Eds[#\ Petroleum Geolo`y of North!West Europe "pp[ 742Ð 753#[ London] Graham and Trotman[ Vail\ P[ R[\ + Wornardt\ W[ W[ "0889#[ Well log Seismic Sequence Stratigraphy] An Integrated Tool for the 89|s[ In J[ M[ Armentrout + R[ F[ Perkins "Eds[#\ Sequence Strati`raphy as an Exploration Tool] Concepts and Practices from the Gulf Coast "pp[ 268Ð277#[ 00th Ann[ Res[ Conf[ Gulf Coast Section[ Soc[ Econ[ Paleon[ Mineral[ Walker\ R[ G[ "0867#[ Deep Water Sandstone Facies and Ancient Sub! marine Fans] Models for Exploration for Stratigraphic Traps[ Am[ Assoc[ Petrol[ Geol[ 51\ 821Ð855[ Walker\ R[ G[ "0874#[ Mudstones + Thin!Bedded Turbidites Associated with the Upper Cretaceous Wheeler Gorge Conglomerates\ Cal! ifornia] A possible channel!levee complex[ J[ Sedim[ Petrol[ 44\ 168Ð 189[ Weimer\ P[ "0889#[ Sequence Stratigraphy\ facies geometry and depo! sitional history of the Mississippi Fan\ Gulf of Mexico[ Bull[ Am[ Assoc[ Petrol[ 63\ 314Ð342[

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development of submarine slope!apron and basin!~oor fans in the Late Jurassic!Early Cretaceous of the South Viking Graben[ Basin Research[ Woodrow\ D[ L[\ + Isley\ A[ M[ "0872#[ Facies\ topography and sedi! mentary processes in the Catskill Sea "Devonian#\ New York and Pennsylvania[ GSA Bulletin 83\ 348Ð369[