Abstract
The structure of subsurface fault networks,which has a significant effect on hydrocarbon migration,is inherently difficult to recognize and map.3D seismic surveys provide an opportunity to map the fault system within a carbonate reservoir of Xinchang in the western Sichuan Basin,China.We calculated attributes from the seismic reflection data that covers an area of 1330 km~2,including variance,edge detection,dip-magnitude and dip azimuth.We focused on the Triassic Leikoupo Formation of dolostone,at ~6 km depth,adjacent to the Longmen Shan thrusting range.The mapped attributes display(1)a primary network of faults in an orthogonal pattern in the anticline,striking East-West and North-South,and(2)a secondary,conjugate fault set in the fold limb,striking Northeast and Northwest with a length range of 1-10 km.The latter set of conjugate faults are confined to a 300 m-thick layer of dolostone,diminishing into underlaying unit of anhydrite.We envision that the conjugate fault networks and associated fractures enhance gas charging and reflect a model of self-sourced migration and accumulation in the Leikoupo Formation.These results are significant for sweet-spot evaluation of carbonate reservoirs in the Sichuan Basin,and provide insights for understanding the migration of subsurface fluids.
NSTL