Extensional Fault System Evolution and Reservoir Connectivity
Darrell W. Sims, Alan P. Morris, David A. Ferrill, Rasoul Sorkhab, 2005. "Extensional Fault System Evolution and Reservoir Connectivity", Faults, Fluid Flow, and Petroleum Traps, Rasoul Sorkhabi, Yoshihiro Tsuji
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Sandbox analog modeling experiments provide new insights into the effects of fault geometry on reservoir connectivity. During progressive distributed extension, three phases of fault system evolution are apparent. In Phase I, geometrically simple faults nucleate rapidly at a large number of sites throughout the deforming region. This is followed by Phase II, in which faults link and increase in trace length. Phase III is characterized by a quasi-steady-state nucleation and linkage of faults. Reservoir connectivity has many components; here, we focus on fault-controlled connectivity, which can be viewed from two complementary perspectives: rock mass connectivity (continuity of rock between and around faults) and fault network connectivity. Which of these perspectives is adopted depends on whether faults cutting the reservoir act as barriers to flow (e.g., in highly porous sandstone reservoirs) or conduits for flow (e.g., in fractured carbonate reservoirs). We use two measures of fault-controlled connectivity: (1) a fault density measure derived from the number of intersections between faults and potential flow paths and (2) the ratio of the number of fault tips to the number of faults. Taken together, these characteristics convey both the transmissivity characteristics and the ultimate leakiness of the reservoir.
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Japan National Oil Corporation (JNOC) (presently Japan Oil, Gas and Metals National Corporation) launched a multidisciplinary and international project on the Evaluation of Traps and Seals in 1997. The project ended in 2003. This publication resulted from that project and includes JNOC research articles as well as contributions from industry and academia. The 17 papers in this volume cover topics such as a method to estimate the amount of oil/gas accumulation using the concept of equivalent grain size in seal rock, and oil/gas migration to and spill-point geometry of petroleum traps; two case studies of fault seal assessment applied to normal faults in Tertiary clastic reservoirs in offshore Sarawak and offshore Gulf of Thailand; and physical analog studies of the development of extensional faults. This publication also contains a valuable bibliography of nearly 1000 additional articles and books published on fault traps, fault seal processes, and fault-related fluid flow in sedimentary basins, for use as a reference tool to delve into publications preceding this volume.