- Email: [email protected]
Fine-Grained Turbidite Systems
Marine and Petroleum Geology 18 (2001) 1029
www.elsevier.com/locate/marpetgeo
Book Review Fine-Grained Turbidite Systems Arnold H. Bouma, Charles G. Stone (Eds.); American Association of Petroleum Geologists, 2000, ISBN: 089181-353-5, Price: $103, £61.75 (AAPG Member $74; Geological Society Fellow £53.25) The last ®fteen years have seen a switch in focus of oil and gas exploration away from the continents and their adjacent shelves into the deeper water areas of the slope. Wells in water depths of 2000 m are now not unusual. This switch has been rewarded by considerable success in the discovery of billions of barrels of oil, notably in the Gulf of Mexico, offshore Brazil and West Africa. The principal exploration targets are turbidites in stacked meandering channel systems mainly of Tertiary age that can be imaged easily using modern 3D seismic data Ð the channels are often too small to be con®dently mapped using 2D seismic data. Aided by DHIs and seismic attribute analysis, exploration has proven to be relatively low risk. However, ultimate success will be dependent on successful exploitation and development of these ®elds. Economics will require small numbers of development wells and excellent reservoir performance is then critical. However, surprisingly little is known of the heterogeneity of the turbidites in channel sands especially in ®ne grained systems. The much studied sand-rich systems do not offer appropriate analogues because the large volume of mud in ®ne grained systems results in quite different patterns of internal architecture at bed to sequence scales. This book attempts to bridge the knowledge gap by means of an excellent set of experimental, outcrop and case studies that document the main features of these systems providing valuable context for reservoir geoscientists. The book is arranged in a topical format so that larger scale aspects are presented ®rst leading to progressively greater detail. As noted by the editors, the objective is illustration of the depositional and stratigraphic characteristics rather than location. That said, it should be noted that 18 of the 28 chapters deal mostly with turbidites in the Karroo Basin of South Africa and also Oklahoma and West Texas. None of these settings can be regarded as wholly comparable to the deepwater passive marginsettings. Nonetheless, using the dictum that `analogue is
merely demonstration and not proof'; these analogues provide a very useful compilation of reservoir architecture at a variety of scales useful to both the explorer and the reservoir geoscientist. The outcrop examples span the gamut from basin evolution through to sequence stratigraphy to reservoir characterisation and detailed sedimentological studies in a variety of fan settings, ancient and modern. One of the problems in using outcrop data lies in matching their vertical and horizontal scales with those of seismic data and the limited size of outcrops often prevents a wider view. However, the beautiful exposures in the Karroo Basin in particular allow for some con®dence in de®ning lateral variability and heterogeneity. Two of the remaining papers deal with experimental modelling of debris ¯ows and turbidity currents Ð approaches that offer considerable potential insight into the uniqueness or otherwise of depositional process and hence reservoir vs non-reservoir distribution in individual channel systems. While only three papers deal with seismic imaging of deepwater turbidite systems (Gulf of Mexico and Nigeria), this is more than compensated by the excellent images on the CD-ROM provided with the book; a very useful and innovative addition that can be used independently of the book. Two other chapters deal with Lithology calibration and evaluation of turbidites using borehole imaging of various kinds. The emphasis on outcrop studies is appropriate and provides the reader with some critical datasets at a variety of scales useful to help understand internal architecture and sandbody geometries. Equally, the seismic data are valuable though there remains a great deal of challenge and uncertainty in interpreting reservoir architecture even from high-resolution 3D seismic data. Overall, this is a useful and timely book. It is lavishly illustrated in black and white as well as full colour. It will be very useful to explorers, reservoir geoscientists and researchers in this ®eld. A strongly recommended buy for your company, institution or personal library. David G. Roberts* BP Exploration, Building C, Chertsey Road, Sunbury on Thames, Middlesex TW16 7LN, UK E-mail address: [email protected]
* Tel.: 144-1932-760545. 0264-8172/01/$ - see front matter PII: S0264-817 2(01)00021-6
www.elsevier.com/locate/marpetgeo
Book Review Fine-Grained Turbidite Systems Arnold H. Bouma, Charles G. Stone (Eds.); American Association of Petroleum Geologists, 2000, ISBN: 089181-353-5, Price: $103, £61.75 (AAPG Member $74; Geological Society Fellow £53.25) The last ®fteen years have seen a switch in focus of oil and gas exploration away from the continents and their adjacent shelves into the deeper water areas of the slope. Wells in water depths of 2000 m are now not unusual. This switch has been rewarded by considerable success in the discovery of billions of barrels of oil, notably in the Gulf of Mexico, offshore Brazil and West Africa. The principal exploration targets are turbidites in stacked meandering channel systems mainly of Tertiary age that can be imaged easily using modern 3D seismic data Ð the channels are often too small to be con®dently mapped using 2D seismic data. Aided by DHIs and seismic attribute analysis, exploration has proven to be relatively low risk. However, ultimate success will be dependent on successful exploitation and development of these ®elds. Economics will require small numbers of development wells and excellent reservoir performance is then critical. However, surprisingly little is known of the heterogeneity of the turbidites in channel sands especially in ®ne grained systems. The much studied sand-rich systems do not offer appropriate analogues because the large volume of mud in ®ne grained systems results in quite different patterns of internal architecture at bed to sequence scales. This book attempts to bridge the knowledge gap by means of an excellent set of experimental, outcrop and case studies that document the main features of these systems providing valuable context for reservoir geoscientists. The book is arranged in a topical format so that larger scale aspects are presented ®rst leading to progressively greater detail. As noted by the editors, the objective is illustration of the depositional and stratigraphic characteristics rather than location. That said, it should be noted that 18 of the 28 chapters deal mostly with turbidites in the Karroo Basin of South Africa and also Oklahoma and West Texas. None of these settings can be regarded as wholly comparable to the deepwater passive marginsettings. Nonetheless, using the dictum that `analogue is
merely demonstration and not proof'; these analogues provide a very useful compilation of reservoir architecture at a variety of scales useful to both the explorer and the reservoir geoscientist. The outcrop examples span the gamut from basin evolution through to sequence stratigraphy to reservoir characterisation and detailed sedimentological studies in a variety of fan settings, ancient and modern. One of the problems in using outcrop data lies in matching their vertical and horizontal scales with those of seismic data and the limited size of outcrops often prevents a wider view. However, the beautiful exposures in the Karroo Basin in particular allow for some con®dence in de®ning lateral variability and heterogeneity. Two of the remaining papers deal with experimental modelling of debris ¯ows and turbidity currents Ð approaches that offer considerable potential insight into the uniqueness or otherwise of depositional process and hence reservoir vs non-reservoir distribution in individual channel systems. While only three papers deal with seismic imaging of deepwater turbidite systems (Gulf of Mexico and Nigeria), this is more than compensated by the excellent images on the CD-ROM provided with the book; a very useful and innovative addition that can be used independently of the book. Two other chapters deal with Lithology calibration and evaluation of turbidites using borehole imaging of various kinds. The emphasis on outcrop studies is appropriate and provides the reader with some critical datasets at a variety of scales useful to help understand internal architecture and sandbody geometries. Equally, the seismic data are valuable though there remains a great deal of challenge and uncertainty in interpreting reservoir architecture even from high-resolution 3D seismic data. Overall, this is a useful and timely book. It is lavishly illustrated in black and white as well as full colour. It will be very useful to explorers, reservoir geoscientists and researchers in this ®eld. A strongly recommended buy for your company, institution or personal library. David G. Roberts* BP Exploration, Building C, Chertsey Road, Sunbury on Thames, Middlesex TW16 7LN, UK E-mail address: [email protected]
* Tel.: 144-1932-760545. 0264-8172/01/$ - see front matter PII: S0264-817 2(01)00021-6