Sedimentary Facies Study Of The Third Member Of The Alshan Formation In The Hanan Area

Erlian Basin is located in the north-central part of China'sInner Mongolia Autonomous Region.It is one of the large-scale sedimentary basins on land in China.The Ha'nan area is located in the A'ershan tectonic belt in the eastern A'nan depression of Erlian Basin,the reservoir of the A'ershan Formation is one of the main reservoirs in the southern area,but the exploration effect is not ideal in recent years.Through a large number of previous theoretical studies,it is believed that the A'ershan Formation in the Ha'nan area developed nearshore submarine fan deposition.The coastal subaqueous fan is a typical sedimentary system of the steep slopes of the faulted lacustrine basin,and a large number of oil and gas exploration breakthroughs have been made in the eastern part of China,which is an important oil and gas reservoir.The study of this paper has a good theoretical significance for the study of nearshore underwater fan deposition system,which is of great practical significance to further predict the reservoir distribution and the tapping potential of the old oil field.In this paper,the third member of the A'ershan Formation in Ha'nan area is taken as the research object,and the research results of predecessors are analyzed,Based on the study of regional tectonics and stratigraphy,the stratigraphic contrast and sedimentary source analysis of the study area are carried out.Based on the study of sedimentary facies,the sedimentary microfacies of the third member of the A' ershan Formation are summarized.The evolution and distribution of the sedimentary facies are analyzed,and the sedimentary model of the third member of the A' ershan Formation is analyzed.The following conclusions are obtained:The Ha'nan area is located in the A'nan sag of the Erlian Basin,Inner Mongolia.A'ershan Formation is one of the main reservoirs in the Ha'nan area.The third member of the A'ershan Formation are typical of the granite and sedimentary facies.The stratum is developed by the paleo-uplift,the buried hill and the fault control.The overall performance is"the north and the south",and the thickness of the strata in the Shannan and Hadong sags is above 200m,and the Ha'nan buried hill and eastern Shayinwusu raised the formation is missing.Based on the analysis of the composition maturity,the content of cuttings in the study area,the analysis of lithology,there are three source directions in the north,east and south.Through the analysis of debris particle structure,the Menggulin raised in the north and the Shayinwusu raised in the east may be the main source area,and the Sunite uplift in the south may be the secondary source area.The third member of the A'ershan Formation in the Ha'nan area is divided into fan-root,fan and sub-subfacies,the fan root is divided into the main channel and the main channel between the micro-phase,the fan is divided into braided waterways,braided waterway and fan front edge three micro-phase.The subterranean submarine fan is mainly developed at the bottom of the third member,and the fan body is developed and gradually evolves into lake sediments.The fan body development and sedimentary facies are distributed by the lake edge ridge,buried hill and sag obvious.The edge of the lake basin rupture,the fossil edge of the development of the fan subfamily,buried hill near the development of fan subfacies,depression area for the fan and lake sediments.In the eastern part of the study area,the development of the underwater submarine of Shayinwusu is better,and the southern A'nan slope is generally developed,and gradually migrate to lake sediments to Ha'nan Buried Hill-Shannan sag and Hadong sag.The coastal subaqueous fan is mostly developed in the rift basin,with gravity flow and near source deposition as the main features.Under the action of the extensional stress of the basin,the faulted lake basin is formed,which is the tectonic environment of the underwater aquifers.In the faulted lake basin,the steep slope formed by the same fault is the paleogeomorphological condition required for the development of nearshore aquifers.The ancient bumps at the edge of the lake basin provide the necessary sediment for the development of the fan.Basin structure continued active,uniform settlement of the lake invasion period,favorable for large underwater fan development.The fractal edge of the lake basin,buried hill,pavement and other micro-geomorphology,control the fan sub-phase(fan root,fan,fan end)development and distribution.The fan root of the main channel and the fan in the braided channel gritstone,is an important oil and gas reservoir.