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Sims, Darrell W.1, Alan P. Morris2, David A. Ferrill1, Rasoul Sorkhabi3, Nathan M. Franklin1, Deborah J. Waiting1
(1) CNWRA, Southwest Research Institute, San Antonio, TX 
(2) University of Texas San Antonio, San Antonio, TX 
(3) Energy and Geosciences Institute, University of Utah, Salt Lake City, UT

ABSTRACT: Rapid Evaluation of Extensional Fault-System-Controlled Reservoir Connectivity

We have developed a geometric method for quantifying the effects of extensional fault-systems on reservoir connectivity. Because faults may act as either barriers to (e.g., in highly porous sandstone reservoirs) or conduits for (e.g., in fractured carbonate reservoirs) flow, we evaluate fault controlled connectivity from the complementary perspectives of rock mass connectivity (continuity of rock between and around faults), and fault network connectivity (interconnectedness of faults). During the evolution of fault systems, rock mass connectivity decreases with an increase in fault network connectivity. We use two measures of fault-controlled connectivity: (i) fault density derived from the number of intersections between faults and potential flowpaths, and (ii) the ratio of number of fault tips to number of faults. Taken together, these characteristics convey both the short-term transmissivity in a faulted reservoir and the ultimate leakiness of the reservoir. Our measures of connectivity permit rapid evaluation of the extent to which a randomly placed well is connected to a transmissive reservoir in any horizontal direction using simple reservoir or trapping horizon fault trace maps. This is an important consideration in estimating drained volumes and well spacing in a new field. This geometric method can also be extended into three dimensions if sufficient data are available.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.