Controlling mechanisms of strike-slip faults on development of the Ordovician karst reservoirs in the Tazhong Uplift

Tarim Basin are poorly understood.Seismic attribute of root mean square amplitude was used to predict karst reservoir distribution in the shallow

middle and deep Ordovician on the North Slope of Tazhong Uplift.The results show that most of the karst reservoirs distribute with inheritance in the northeastern and southwestern ends of blocks which are bounded by the NW- and NE-trending faults

especially the deep Ordovician in ZG5 and ZG10 blocks.Such distribution characteristics cannot be interpreted by sedimentary facies and palaeogeomorphology

while strike-slip fault activity could provide a possible interpretation:Right-lateral compress-shear activity of the NW-trending faults induces left-lateral strike-slip activity of the NE-trending faults.The northeastern and southwestern ends of blocks bounded by the NW- and NE-trending faults are located in the intersection area of the NW- and NE-trending faults

where crossed fracture zones induced by faults are well developed.In addition

the strike-slip movements led to local extension in the northeastern and southwestern ends of blocks

while local compression in the northwestern and southeastern ends.Extensional fracturing of rock in local extension area is much easier than compressional fracturing of rock in local compression area for that the tensile strength of rock is much smaller than its compressive strength.The extensional fractures provide migration pathway to dissolution fluid and increases contact area of dissolution fluid and rock

so the northeastern and southwestern ends of blocks have well developed karst reservoirs.The research suggests that the strike-slip fault is one of controlling factors on development of karst reservoirs in the Tazhong Uplift.