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Geology of the Humber Group: Central Graben and Moray Firth
Marineand PetroleumGeology Marine and Petroleum Geology 15 (1998) 379-383
Book Reviews
Geology of the Humber Group: Central Graben and Moray Firth Edited by: Hurst, A., Johnson, H. D., Burley, S. D., Canham, A. C. and Mackretich, D. S. Geological Society Special Publication 114 ; 1997 ; ISBN l-897799-70-5. Price &75 (US$125) Geol. Sot. Member (E33/US$55) This volume represents number 114 in what is now an extensive and generally excellent series of Special Publications of the Geological Society of London. This series has given us access to some admirable volumes in the past. Sedimentation in the Africa Rifts (25) Inversion Tectonics (44) and Classic Petroleum Provinces (50) are amongst those we remember fondly, all of which have contributed much to our understanding of geological process and how petroleum systems work. Unfortunately, we have to conclude that the “Geology of the Humber Group” is unlikely to be numbered with the above volumes. Where, for instance, is the overview paper that puts the Humber group in its regional North Sea and petroleum geological context? As an indication of its significance, we estimate that reservoirs within the group have trapped over 25% of the North Sea’s petroleum resources ; source rocks in the group have sourced well over 90% of the petroleum in the Northern North Sea and seals in the upper part of the unit have trapped some 75% of the reserves in the region. But none of this is to be found in this volume. The book is the product of papers presented at two closely related conferences held in 1994 under the auspices of the Petroleum Group of the Geological Society of London. Although the material references stratigraphy of Upper Jurassic age, (the Humber Group), the content of the volume covers a wide breadth of subject matter which falls within a few general themes. Sub-basin and field case histories account for five of the papers, whilst detailed technique based studies, using specific approaches to understanding basin fill processes, burial history and sediment fill architecture are covered by a further five. The remainder, have as their main theme, sequence stratigraphy and its application of Jurassic playmaking in the Moray Firth and Central Graben basins. Unfortunately, there is no obvious overview paper to put the different themes in context and the volume, in
consequence, lacks continuity and a sense of cohesion. In general, the book is well illustrated including good use of colour and foldouts. However, we found the few lines of text languishing at the base of several figures rather annoying. A small point. A thorough review is presented by Veldkamp et al. on the validity of using a sequence stratigraphic based methodology for Upper Jurassic basin analysis. Integration of biostratigraphy, wireline log data, sedimentology and 3D seismic data reveals the limitations of sequence models in a complex spatially evolving basin. The interplay of tectonic subsidence, reduced sediment supply and overall transgression inhibit accurate mapping of a Kimmeridgean time-slice. The authors go some way towards testing and evaluating the sequence stratigraphic models presented by BP and Exxon at the Barbican in 1992. They quote general agreement with both schemes but identify several shortcomings in the methodology largely due to biostratigraphic resolution in the BP case and linking all sequence boundaries to the global Haq curve in the Exxon case. However, they conclude that sequence stratigraphy does provide more consistent field scale and regional interpretations, rather than adopting a single discipline methodology. This is elegantly reinforced by Davies et al. who define the application of a genetic sequence framework for onward paleogeographic mapping of time equivalent facies in the Moray Firth. A remarkably similar methodology is presented in the volume by Harker and Rieuf who also use genetic sequences to generate paleogeographic maps, although confusingly introduce further alternative sequence nomenclature. The necessity of having these two papers published in the same volume consecutively, warrants criticism when one or other would surely have demonstrated the application of these stratigraphic techniques. Caruthers et al. introduce to the already encyclopaedic literature the term “low stand sequence set” to describe basinal stratigraphy which may contain subtle stratigraphic turbidite plays. However, the authors do go some way to presenting the temporal evolution of, and mechanisms for, improved sediment flux to deep water environments, during high order sea level lowstands. This really is the only attempt in the volume to use the sequence stratigraphic schemes presented at the Barbican in 1992, in a predictive sense, i.e. “I observe a sequence boundary therefore I predict fans.” The authors elegantly
SO264-8172/98/T-see front matter 0 1998 Elsevier Science Ltd. All rights reserved PII: SO264~8172(98)00006-3
380
Book twiewsIMurine
und Pmoleutn
demonstrate the relationship of basin margin incision and the development of sequence boundaries to the downdip prediction of coarse grained, sediment gravity flow deposits. A more detailed trace fossil (ichnotabric) analysis over the Kittiwake field is presented by Martin and Pollard. Building on the concepts of Gawthrope et al. from the last Barbican Conference, the authors identify a number of key sedimentological and environmental controls on strata1 surface development from cores. These are then related to systems tract bounding surfaces and correlated in an east-west transect across the field. Interestingly, the systems tract correlation differs from that of Veldkamp rt al. and highlights how sequence interpretations can differ for the same area using approaches with different emphasis. In summary, despite the genetic sequence stratigraphic scheme defined for the Jurassic by Partington et al. in the 1993 Barbican proceedings, it is certainly confusing to be faced with a plethora of new nomenclature, and unnecessary new lithostrstigraphic terminology. This only serves to confuse the reader and detracts from the quality of the research. Given this, it would have been useful for the editors to encourage each of the authors of these papers to relate their terminology to the previously published scheme. The only paper in the book to address the tectonic evolution of the Humber Group is authored by Frost and Rose. Their idea of a fairly quiescent Upper Jurassic punctuated by compressive strike-slip movements provides an interesting alternative to the more conventional polyphase rift model. However, in the absence of a regional tectonic setting paper in the volume (cf papers by Underhill and Partington and Rattey and Hayward in the Barbican volume) this paper cannot be placed in its true context i.e. that of a poorly accepted alternative model. In a volume purporting to be representative of our understanding of the Geology of the Humber Group, this paper could be misleading to readers who may be new to the geology of the area. The next group of papers include those which focus on specialist approaches to understanding detailed geological aspects of Humber Group lithologies. They address widely varied concepts including diagenesis, thermal maturation, provenance analysis and process sedimentology leading to an assessment of reservoir quality. Hallsworth et al. nicely unravel the complexities of using provenance sensitive minerals to derive sediment dispersal patterns in the vicinity of the Halibut Horst. Using stratigraphically constrained samples from both shallow and deep marine sands, the structural evolution of the Halibut Horst and adjacent basins is presented. Gowland presents a regional Fulmar Formation ich-
Grolog~
15 (1YYX) 379 ~383
nofacies analysis, identifying 12 major sedimentary facies types. Importantly, the analysis takes into account the influence of underlying Zechstein salt in creating accommodation space on the Fulmar shelf. Canon and Gowland develop the above analysis to its logical conclusion by addressing the differing reservoir characteristics of the various Fulmar facies types using a five well core dataset from Quad 2 1. In a useful contribution, Freer et ul. discuss the geology and exploration history of the Fladen Ground Spur. Little has been published to date on the area : no discoveries therefore little romance. This paper is an example of a well researched, well presented study. The paper significantly adds to our knowledge and understanding of the northern depositional margin of the Humber Group. The final group of papers detail a series of prospect and field based case studies. McCants and Burley present, in our view, an excellent analysis of the deeper Piper sand play in the Witch Ground Graben. The problems during the appraisal of this prospect due to a severe diagenetic overprint on primary depositional porosity are a timely reminder of the reservoir problems that may be encountered if future exploration in the Humber group is to be targeted at deeper reservoirs. Dickinson describes the 15year appraisal of the Puffin Field. This is a good example of how geological models can change during the course of the appraisal of a structurally and stratigraphically complex field. The author presents probably the best example we have seen of the application of the generally accepted salt/sediment pod model for the Central North Sea, to field appraisal. The analysis highlights, as ever, the value of a good 3D and well dataset. Based on papers presented only two years after the Barbican Conference of 1992, we feel that this volume adds little to the understanding of the Upper Jurassic in the Northern North Sea that cannot be found in the original Barbican proceedings. If you are interested in exploration and production in the Humber Group, we would refer readers to the more extensive Barbican volume. If you already own or have access to the Barbican proceedings, this Special Publication contains several papers which are complementary to the papers presented at the Barbican. Perhaps it would have been better to see the best of the papers published as a thematic set in either the Journal of the Geological Societ_v or the excellent Petroleum Geoscience Journal, products of the same Geological Society publishing house. S. I. Fraser Amerudu
Hess Ltd, London
A. J. Fraser BP Exploration,
Houston
Texus
Book Reviews
Geology of the Humber Group: Central Graben and Moray Firth Edited by: Hurst, A., Johnson, H. D., Burley, S. D., Canham, A. C. and Mackretich, D. S. Geological Society Special Publication 114 ; 1997 ; ISBN l-897799-70-5. Price &75 (US$125) Geol. Sot. Member (E33/US$55) This volume represents number 114 in what is now an extensive and generally excellent series of Special Publications of the Geological Society of London. This series has given us access to some admirable volumes in the past. Sedimentation in the Africa Rifts (25) Inversion Tectonics (44) and Classic Petroleum Provinces (50) are amongst those we remember fondly, all of which have contributed much to our understanding of geological process and how petroleum systems work. Unfortunately, we have to conclude that the “Geology of the Humber Group” is unlikely to be numbered with the above volumes. Where, for instance, is the overview paper that puts the Humber group in its regional North Sea and petroleum geological context? As an indication of its significance, we estimate that reservoirs within the group have trapped over 25% of the North Sea’s petroleum resources ; source rocks in the group have sourced well over 90% of the petroleum in the Northern North Sea and seals in the upper part of the unit have trapped some 75% of the reserves in the region. But none of this is to be found in this volume. The book is the product of papers presented at two closely related conferences held in 1994 under the auspices of the Petroleum Group of the Geological Society of London. Although the material references stratigraphy of Upper Jurassic age, (the Humber Group), the content of the volume covers a wide breadth of subject matter which falls within a few general themes. Sub-basin and field case histories account for five of the papers, whilst detailed technique based studies, using specific approaches to understanding basin fill processes, burial history and sediment fill architecture are covered by a further five. The remainder, have as their main theme, sequence stratigraphy and its application of Jurassic playmaking in the Moray Firth and Central Graben basins. Unfortunately, there is no obvious overview paper to put the different themes in context and the volume, in
consequence, lacks continuity and a sense of cohesion. In general, the book is well illustrated including good use of colour and foldouts. However, we found the few lines of text languishing at the base of several figures rather annoying. A small point. A thorough review is presented by Veldkamp et al. on the validity of using a sequence stratigraphic based methodology for Upper Jurassic basin analysis. Integration of biostratigraphy, wireline log data, sedimentology and 3D seismic data reveals the limitations of sequence models in a complex spatially evolving basin. The interplay of tectonic subsidence, reduced sediment supply and overall transgression inhibit accurate mapping of a Kimmeridgean time-slice. The authors go some way towards testing and evaluating the sequence stratigraphic models presented by BP and Exxon at the Barbican in 1992. They quote general agreement with both schemes but identify several shortcomings in the methodology largely due to biostratigraphic resolution in the BP case and linking all sequence boundaries to the global Haq curve in the Exxon case. However, they conclude that sequence stratigraphy does provide more consistent field scale and regional interpretations, rather than adopting a single discipline methodology. This is elegantly reinforced by Davies et al. who define the application of a genetic sequence framework for onward paleogeographic mapping of time equivalent facies in the Moray Firth. A remarkably similar methodology is presented in the volume by Harker and Rieuf who also use genetic sequences to generate paleogeographic maps, although confusingly introduce further alternative sequence nomenclature. The necessity of having these two papers published in the same volume consecutively, warrants criticism when one or other would surely have demonstrated the application of these stratigraphic techniques. Caruthers et al. introduce to the already encyclopaedic literature the term “low stand sequence set” to describe basinal stratigraphy which may contain subtle stratigraphic turbidite plays. However, the authors do go some way to presenting the temporal evolution of, and mechanisms for, improved sediment flux to deep water environments, during high order sea level lowstands. This really is the only attempt in the volume to use the sequence stratigraphic schemes presented at the Barbican in 1992, in a predictive sense, i.e. “I observe a sequence boundary therefore I predict fans.” The authors elegantly
SO264-8172/98/T-see front matter 0 1998 Elsevier Science Ltd. All rights reserved PII: SO264~8172(98)00006-3
380
Book twiewsIMurine
und Pmoleutn
demonstrate the relationship of basin margin incision and the development of sequence boundaries to the downdip prediction of coarse grained, sediment gravity flow deposits. A more detailed trace fossil (ichnotabric) analysis over the Kittiwake field is presented by Martin and Pollard. Building on the concepts of Gawthrope et al. from the last Barbican Conference, the authors identify a number of key sedimentological and environmental controls on strata1 surface development from cores. These are then related to systems tract bounding surfaces and correlated in an east-west transect across the field. Interestingly, the systems tract correlation differs from that of Veldkamp rt al. and highlights how sequence interpretations can differ for the same area using approaches with different emphasis. In summary, despite the genetic sequence stratigraphic scheme defined for the Jurassic by Partington et al. in the 1993 Barbican proceedings, it is certainly confusing to be faced with a plethora of new nomenclature, and unnecessary new lithostrstigraphic terminology. This only serves to confuse the reader and detracts from the quality of the research. Given this, it would have been useful for the editors to encourage each of the authors of these papers to relate their terminology to the previously published scheme. The only paper in the book to address the tectonic evolution of the Humber Group is authored by Frost and Rose. Their idea of a fairly quiescent Upper Jurassic punctuated by compressive strike-slip movements provides an interesting alternative to the more conventional polyphase rift model. However, in the absence of a regional tectonic setting paper in the volume (cf papers by Underhill and Partington and Rattey and Hayward in the Barbican volume) this paper cannot be placed in its true context i.e. that of a poorly accepted alternative model. In a volume purporting to be representative of our understanding of the Geology of the Humber Group, this paper could be misleading to readers who may be new to the geology of the area. The next group of papers include those which focus on specialist approaches to understanding detailed geological aspects of Humber Group lithologies. They address widely varied concepts including diagenesis, thermal maturation, provenance analysis and process sedimentology leading to an assessment of reservoir quality. Hallsworth et al. nicely unravel the complexities of using provenance sensitive minerals to derive sediment dispersal patterns in the vicinity of the Halibut Horst. Using stratigraphically constrained samples from both shallow and deep marine sands, the structural evolution of the Halibut Horst and adjacent basins is presented. Gowland presents a regional Fulmar Formation ich-
Grolog~
15 (1YYX) 379 ~383
nofacies analysis, identifying 12 major sedimentary facies types. Importantly, the analysis takes into account the influence of underlying Zechstein salt in creating accommodation space on the Fulmar shelf. Canon and Gowland develop the above analysis to its logical conclusion by addressing the differing reservoir characteristics of the various Fulmar facies types using a five well core dataset from Quad 2 1. In a useful contribution, Freer et ul. discuss the geology and exploration history of the Fladen Ground Spur. Little has been published to date on the area : no discoveries therefore little romance. This paper is an example of a well researched, well presented study. The paper significantly adds to our knowledge and understanding of the northern depositional margin of the Humber Group. The final group of papers detail a series of prospect and field based case studies. McCants and Burley present, in our view, an excellent analysis of the deeper Piper sand play in the Witch Ground Graben. The problems during the appraisal of this prospect due to a severe diagenetic overprint on primary depositional porosity are a timely reminder of the reservoir problems that may be encountered if future exploration in the Humber group is to be targeted at deeper reservoirs. Dickinson describes the 15year appraisal of the Puffin Field. This is a good example of how geological models can change during the course of the appraisal of a structurally and stratigraphically complex field. The author presents probably the best example we have seen of the application of the generally accepted salt/sediment pod model for the Central North Sea, to field appraisal. The analysis highlights, as ever, the value of a good 3D and well dataset. Based on papers presented only two years after the Barbican Conference of 1992, we feel that this volume adds little to the understanding of the Upper Jurassic in the Northern North Sea that cannot be found in the original Barbican proceedings. If you are interested in exploration and production in the Humber Group, we would refer readers to the more extensive Barbican volume. If you already own or have access to the Barbican proceedings, this Special Publication contains several papers which are complementary to the papers presented at the Barbican. Perhaps it would have been better to see the best of the papers published as a thematic set in either the Journal of the Geological Societ_v or the excellent Petroleum Geoscience Journal, products of the same Geological Society publishing house. S. I. Fraser Amerudu
Hess Ltd, London
A. J. Fraser BP Exploration,
Houston
Texus