This book results from a conference, ‘The Deliberate Search for the Stratigraphic Trap – Where Are We Now?’, held in London in 2004. In their introduction the editors state that ‘in-depth understanding of analogue fields . . . and . . . deep insights . . . were generally not well demonstrated’. Judging from the published record this seems fair comment. The contents, which could in several cases have been refereed more rigorously, fall into four groups.
The first, authored by consultants, comprises three papers dealing with corporate strategy, organization and procedures for successful pursuit of stratigraphic plays, based largely on global lookbacks in which prices and evolving technologies might have figured more prominently. The approach in all is from a prospect portfolio perspective; conclusions are now surely fairly well known but at least stress the need to fund and conserve appropriate levels of long-term information gathering to steepen expectation curves. Young professionals and senior managers alike should heed what is surely a cri de coeur from Binns that ‘frequent re-organizations . . . divert attention away from the technical process’.
The second, authored by staff of the Department of Trade and Industry and the British Geological Survey, contains four papers promoting the potential for stratigraphic traps in various regions of the UK Continental Shelf. To what extent the ‘leads’ illustrated are calibrated evaluations or conceptual arm-waving is unclear.
The third, authored by industry staff, includes three case history papers. That by Godo is an informative integration of sedimentology, sequence stratigraphy and rock properties employed in pursuit of an amplitude-supported gas play in the Miocene of the Gulf of Mexico. The account of the pre-discovery evaluation of Buzzard in the UK North Sea allows British Gas staff to give themselves a well-deserved pat on the back. The promotional story on the Indonesian rift plays sets out a simple play concept using only 2D seismic data and does not discuss rock properties.
The fourth, authored by academics, is a mixed bag of four papers. It includes an exhaustive geometrical classification of seals with no reference to their sedimentology or rock properties and geometrical evaluation of the pinch-out of turbidites against a confining slope without sedimentological insight. The paper on sand ‘extrudites’ nicely mixes seismic and field descriptions of these volumetrically minor stratigraphic curios. An interesting discussion of visual cognition pitfalls in seismic display has general application.
Exploration acreage is too valuable to evaluate solely in terms of structural closures; the more so as high oil prices seem here to stay. Interpreters need to conceptualize all possible closed contours of hydrocarbon fluid potential at spatially complex reservoir/seal interfaces in a context of time-variant access to charge, structural deformation, compaction/diagenesis and dynamic basinal water flow. From this perspective the book conspicuously fails to adress two technical issues that are commonly so much more critical in the definition/evaluation of stratigraphic traps than for layer-cake geometries in structural traps: namely loop-level imaging and the calibration/prediction of rock properties. Shooting 3D seismic is only a beginning. For example, how best should one preserve true relative amplitudes through the seismic processing sequence, generate sedimentologically-defensible horizon attribute maps, design sedimentologically-smart horizon-picking algorithms, best use AvO and dedicated shear wave data in determination of lithology/pore-fill, trade large offsets against bandwidth? The need to explore for stratigraphic traps is obvious – what we want are better tools.
Creative sedimentary geophysicists will get little technical advice or inspiration from this book, nor should it compete strongly for scarce library funds.
