Sedimentary Filling Evolution And Resource Potential Evaluation In The North Area Of Huimin Sag

The small-scale subsags in the north part of Huimin sag include Yangxin subsag, Zizhen subsag, Liuzhong subsag and Lizezhen subsag, and their structural evolution was mainly controlled by the major faults named Yangxin fault and North Zizhen fault. Fracturing dominated structural evolution and sedimentary filling in these subsags. The small subsags have undergone mega-depression tectonics unit during sedimentation of Kongdian Formation, to be divided by Linfanjia structure during sedimentation of the fourth member of Shahejie formation (Es4), to be small subsags under the control of the differential fault activity during sedimentation of the third member of Shahejie formation (Es3).On basis of analysis on single well sedimentary facies, seismic facies and electrofacies, the paper studied provenance direction and distribution rules of depositional system of Kongdian Formation, Es4, Es3 and Es1. Evaluation on reservoir properties indicated that sedimentary microfacies dominated reservoir performance. The paper made systematic research on igneous rock in aspects of seismic facies, electrofacies and their distribution in Yangxin subsag. The paper also examined relationship between igneous rock and reservoir forming. Existence of igneous rock resulted in increase in geothermal gradient, reformed geochemical field, accelerated evolution of source rock, and formed traps related with igneous rock.The paper clarified genesis of petroleum in small-scale subsags in the north part of Huimin sag, and evaluated quality and generation potential of source rock in Es4, Es3 and Es1. Comparison and optimization results showed that exploration potentiality in Yangxin Subsag is the biggest among all the subsags in the north part of Huimin sag, therefore, Yangxin subsag is the preferable exploration area.The paper studied reservoir types in these small subsags. It analyzed reservoir features and key factors controlling reservoir forming in different horizon such as mature oil in the Es4, low-mature oil Es3, biogas in Es1 and mantle genesis carbon dioxide gas. Exploration strategy in Yangxin subsag was clarified: major exploration formation is mature oil in Es4, with low-mature oil in Es3, biogas in Es1 and mantle genesis CO2 serve as accessory orientation, major exploration orientation is Huicheng nosing structure in the middle part and the Shangdian structural belt in the east part.