Integrated Geophysics Study And Deeply Structure Distinguish In Changling Fault Depression

Changling fault depression is a large-scale fault depression in Songliao basin with complicated deep geological structure and developed igneous rocks. It is difficult to obtain the high-quality igneous rocks and information of basement reflective layer by seismic data with great depth. And the number of deep exploratory wells is less, the available information is limited, and the research is not enough systematic, comprehensive and thorough, so that the process of deep oil and gas exploration in this area is restricted. Therefore, how to effectively solve these deep geological structural features, such as the fault structure, distribution and thickness of volcanic rocks, lithology of the basement and the undulating morphology, is the key of deep oil and gas exploration in Changling fault depression.In this paper, on the basis of geology, seism, drilling well, petro-physical property, gravimetric and magnetic measurements and CEMP data, and guided by the Professor Liu Guangding’s principle of interpretation "one, two, three, and more", integrated geophysical technology are applied to realizing the systematic inversion of deep structure in Changling fault depression. Using strengthened means of fracture information such as derivative in the horizontal direction, sub-domain filtering and the horizontal total gradient, to extract the information that reflects the fracture of gravity, magnetic and electric anomaly, then acquire105basement faults with great depth, and combining seismic, geological and other known data to research the distributive law of fracture structure in Changling fault depression, and the northeast, north-south and northwest trending faults control the distributive pattern of fault-concave and fault-convex. According to magnetic characteristics of volcanic rocks, we adopt wavelet analysis to realize the decomposition of magnetic anomalies in different scales, and adopt the wavelet transfer detail anomalies to acquire the distribution of neutral-basic volcanic rocks in different depths and scales, and then the distributive range of volcanic rocks on the research area is delineated indirectly. Seism-gravity joint inversion method is applied to strip the gravity effects and deep regional field above the T4strata, and the basement structure characteristics are discussed, that is, lithology of the basement in this area is complicated, and Carboniferous-Permian shallow metamorphic rocks and Hercynian, Yanshanian intrusive rocks are developed on the region, which are respectively distributed in the central of the work region, and mainly distributed in the east and west sides. The distribution of Pre-sinian strata exists in the eastern part of the C-P basement. Take advantage of the improved method of Parker and profile seism-gravity joint inversion, inversion of the substrate top depth is realized, further isopach maps T4-T5are obtained, namely:Yingcheng group, Shahezi group, Huoshiling group parallel layer isopach maps, and the overall variation of thickness between parallel layer is rendered as "in the east and west is thin, and in the middle is thick", Yingcheng group, Shahezi group, Huoshiling group are the most developed in the central of Changling fault depression, and there are two developmental centers:Changling fault-concave and Qian’an fault-concave. Several favorable local structures are designated by vertical second and fourth derivative anomaly of gravity anomaly on the spatial domain. The prospect of deep oil and gas exploration in Changling fault depression is evaluated by combining the petroleum geological conditions and integrated geophysical research results. And three class I prospective areas are pointed out, namely:Yaoyingtai-Darhan fault-convex, Changling pasture fault-concave and Qian’an fault-concave. Otherwise, there are three class II prospective areas, namely:Chaganhua fault-concave, Daannan fault-convex and the western section of Sugongtuo-Longfengshan fault terrace.