Graham Yielding, 2015. "Trapping of buoyant fluids in fault-bound structures", Industrial Structural Geology: Principles, Techniques and Integration, F. L. Richards, N. J. Richardson, S. J. Rippington, R. W. Wilson, C. E. Bond
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Structural traps comprise surfaces having high capillary threshold pressure for fluid phases such as hydrocarbon or CO2. Traps may include top-seal, bottom-seal and side-seal surfaces, the latter commonly being faults. Faults may form seals by juxtaposition or by fault-rock. The first step in fault characterization is mapping the distribution of offset layers at the fault surface. This pattern (‘Allan diagram’) comprises the separation polygons. These same lines define the displacement distribution on the fault, and so can also be used as a quality-check of the interpretation. They are also a fundamental part of horizon maps. Despite their central role in subsurface mapping, construction of fault polygons remains a weak step in the workflow in many E&P companies. To characterize fault-rock effects, it is usual to consider an upscaled proxy such as shale gouge ratio (SGR), with the assumption that high SGR represents clay smears and low SGR represents clay-poor fault rock. Suitable estimates of hydraulic properties can then be applied to different parts of the fault surface. The property distribution on the fault side-seals allows an estimate of the maximum hydrocarbon column height that the trap might contain, by comparing the multiple potential leak-points and finding which predicts the shallowest contact.
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Industrial Structural Geology: Principles, Techniques and Integration
The practical application of structural geology in industry is varied and diverse; it is relevant at all scales, from plate-wide screening of new exploration areas down to fluid-flow behaviour along individual fractures. From an industry perspective, good structural practice is essential since it feeds into the quantification and recovery of reserves and ultimately underpins commercial investment choices. Many of the fundamental structural principles and techniques used by industry can be traced back to the academic community, and this volume aims to provide insights into how structural theory translates into industry practice.
Papers in this publication describe case studies and workflows that demonstrate applied structural geology, covering a spread of topics including trap definition, fault seal, fold-and-thrust belts, fractured reservoirs, fluid flow and geomechanics. Against a background of evolving ideas, new data types and advancing computational tools, the volume highlights the need for structural geologists to constantly re-evaluate the role they play in solving industrial challenges.