Fault Sealing and Mechanical Stratigraphy in Carbonate Reservoirs, Southeast Guizhou, China

Cui, Min ¹; Tang, Liangjie ^1
1 State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China.

Thrust faults in Paleozoic carbonates of the Southeast Guizhou fold-thrust belt provide important analogs for fault deformation and sealing in marine carbonate reservoirs in South China. Based on the structural elements from photomicrograph, outcrop, seismic cross-section, and laboratory data including mechanical properties, petrophysical properties, and capillary pressure, we studied the mechanisms and intensity of deformation across a large, active, uplift-bounding thrust fault zone in platform carbonates. (1) The relatively higher-angle breakthrough faults with large propagation-to-slip develop in massive, competent, clay-poor dolomites, where the bitumen distributes. Faults in massive, incompetent marlites tend to breakup on lower-angle. (2) In less competent clay-rich strata, shale and mudstone beds impede fault propagation across the strike, resulting in fault-related folding.
³ Higher compressive strength associated with massive, clay-poor dolomites generate more fractures for fluid flow. Conversely, the pressure solution seams, filled with clay later, develop in the lower compressive strength associated with marlites.
⁴ The high density of pressure solution seams between overstepping thrust faults are found, which have raised both the effective length of the barrier to fluid flow and the fault sealing potential.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009