Characteristics Of Pre-Cenozoic Basement Structures And Petroleum Prospect Evaluation Of Offshore Area In Xialiaohe Basin

It studies offshore area in Xialiaohe basin in Pre-Cenozoic to give a comprehensible discussion about basic characteristics of basement structures. By using analysis of well logging data and 3D seismic interpretation, it studies the background of regional structures and rifting system. By comparing geologic formation differences in eastern and western Liaoning, the paper also studies the main characteristics of Tanlu rifting activities in different geological periods. With the methods of field geological surveying and well logging data comparison, it gives new opinions to determine cores ages and puts forward favored structure for hydrocarbon basement according to factors of reservoir. It supplies a reference function for exploring oil and gas in offshore area.Xialiaohe offshore area situated in southwest part of Xialiaohe basin, which extends to sea. According to 3D seismic data interpretation, the basement structures of offshore area are depression-uplift arrangement. Marginal fault has a north-east strike controlling the formation of basement and development of caprock in Cenozoic. The major bombes are central uplift and buried hill in Huludao and Yanan. The major depression are in the west and east sag. Marginal faults which are also known as Hanan and Yanan fault, which are the extension of Tanlu rifting system. The faults are extensional normal, some of them are influenced by later strike-slip.Since the early Proterozoic, evident discrepancies of basement stratum formation in eastern and western Liaoning indciate that forming time of Tanlu rifting system should be early than that of unified basement. The discrepancies of caprock stratum also represented Tanlu rifting development is multi-periods. It can infer that formation time of Xialiaohe basin is in Mesozoic. In early stage, it is rifted basin, then it transformed into intracontinental rift in Paleogene . Finally, it disappeared in late Paleogene and formed down-warped basin.According to analysis of well logging data, 3D seismic interpretation and field geological surveying, it inferred the stratigraphic characteristics of basement structures in offshore area in Cenozoic. The exposed stratums in basement are mainly in Archean and Mesozoic. Only few stratums exposed in Paleozoic and no stratums exposed in Proterozoic. The main body of buried hill is crystalline basement with greatest thickness in Archean, but it is relatively thin in Paleozoic and Mesozoic.According to the characteristics of basement structures and academic achievements in Petrology, it forecasts the prospect of hydrocarbon basement structures and it inferred that hydrocarbon buried hills is the main type of basement structure in offshore area, weak structural surface generated by rifting activities and unconformity surfaces is the great carriers of oil and gas. Structural and lithologic trap are main type of traps in basement structures.