Paleo-tectonic Stress Simulation And Fracture Characteristics Of Deep Plutons In Xinchang Area

The gas field of xinchang is situated in the interior of Deyang of Sichuan province.It is buildup by multiple of gas reservoirs.Until now,the 2nd member of xujiahe formation become the main gas producing zone.This reservoir is the typical low-permeability tight sandstone reservoirs,it has the characteristics of deep carving,baddish porosity and strong heterogeneity.But the development level of rock mass fracture systems can greatly improve the capacity of reservoir and interstifial flow.The rock mass fracture systems is the key geological factors to the high-yield gas reservoir.On the basis of making full use of current research achievements,the drilling data,FMI interpretation,experimental test and field outcrop investigation,with the theoretical guidance of structure geology,petroleum geology and rock mechanics,describing and analysising the characteristics of deep rock mass,and study on paleo-tectonic stress fields and rock mess fracture of the 2nd member of xujiahe of the xinchang field with using the mumerical simulation of the finite element.The following knowledge and achievements have been obtained in this thesis:Xinchang field 2nd member of xujiahe xujiahe reservoir has mainly small scale reberse fault,the main trends of the fault is NE.The reservoir fractures are mostly structural fractures.They have the characteristics of middle length,small density,small width and low filling degree.The main trends of the fractures are EW,SN,NE and NW.The result of experimental test show that the 2nd member of xujiahe of xinchang field reservoir has undergone indo-china movement,Yanshan tectonic movement and Himalayan tectonic movement.And the Himalayan tectonic movement has the most strongly impact on rock mess fracture.The distribution character of the paleo-tectonic stress fields and rock mess fracture by the way of finite element numerical simulation show that the degree of rock mess fracture not only relate to the paleo-tectonic stress fields,but also structural shape and formation lithology.The regional of higher rock mess fracture degree always adjacent to the fault and the structural height with shape of banding,and the regional of lower rock mess fracture degree mostly adjacent to the low point of the structural and the gentle zone with the shape of massive.