The Characteristic of Deep Structure and Natural Gas Accumulation in Changling Fault Depression,Southern Songliao Basin

With full use of 2D regional seismic profile,3D seismic data,drilling/well logs information,and high-resolution gravity-magnetic-electric information,the regional geological texture of Changling fault depression in Southern Songliao Basin is systematically dissected.It is believed that Changling fault depression connecting with Gulong fault depression in north is a group of composite fault depressions including lots of primary and secondary sags rather than a single fault depression.In the light of industrial mapping,structural element and zone are divided;geometric and kinematical characteristics of major fractures are analyzed.The strata development and the depression framework are controlled by Qian'an fault,Qianshenzijing fault,Heidimiao fault,Guxi fault,Gudian fault,Daan fault,Haerjin fault and Gujiadian-Fulongquan fault.Among them the Qian'an fault,Qianshenzijing fault and Heidimiao fault are foremost faults controlling depression.The evolution history of the depression is divided into three phases,i.e.basement formation phase,rifting phase,and fault depression reform phase.The reservoir formation condition for various types of gas reservoirs is studied in term of petroleum geology.It is recognized that the deep-seated hydrocarbon gas is coal-type gas,which came from the Shahezi Formation and Huoshiling Formation which deposited in depressing phase,and the deep seated CO2 gas is anorganogene,which mainly came from mantle,and the direction for prospective zone exploration is pointed out.