Structural Features And Hydrocarbon Accumulation In Southern Chaluhe Fault Depression Of Yitong Basin

Yitong Basin is a Cenozoic petroliferous basin,developed in the northern Tanlu fault area,composed by three second grade tectonic units,Moliqing fault and Luxiang fault and Chaluhe fault.In this paper.The study area is located in the southern Chaluhe fault depression,controlled by horder faults,can be divided into four tectonic units: the northwest margin of bruchfalten,Liang Jia tectonic belt,Xin'an Nanpu Sag and Wanchang tectonic belt.Since the beginning of the exploration,it has been proved that this area need the more exploring area of features and the low exploring level and large residual resources,so more analysis and exploring work in oil potential is necessary.This paper,based on theory of modern tectonic geology,using various techniques,such as 3D seismic interpretation,strutural analysis,balance profile reversion and comprehensive,hydrocarbon accumulation condidtion,obtain the following points:(1)In the northwest margin,the strike-slip extension is the majority structural in the early stage,and the strike-slip deformation in the late inversion.(2)In the southern section of Chaluhe fault depression,there are four types of structural assemblages:stepped normal fault,"Y"-shaped combination,"X"-type normal fault and barrier-block pattern.(3)The study area has experienced three stages of evolution in construction,the Paleogene Shuangyang Formation-Wanchang Formation fault-depression period,the Paleogene Qijia Formation stress transition period and the Neogene Jirohe Formation inversion period.(4)The hydrocarbon source rocks of Shuangyang Formation and Huoling Formation reach hydrocarbon generation thresholds in the Oligocene and generate oil and gas.The oil and gas migrate vertically and horizontally along the faults and strata,a part of oil and gas are blocked by early reverse faults forming the fault oil-gas reservoirs,or fault-lithologic reservoirs,the other oil and gas forming the fault-block oil reservoirs or fault-lithologic reservoirs along the late faults in the Wanchang formation and the northwest margin of the Liangjia shallow fault thrust fold belts.