Fault Characteristics And Evolution Of The Eastern Segment Of The Altun Mountains In The Qaidam Basin

At present there have many theses research on the Altun fault belt which mainly using field outcrop data to analyze the property and active periods of fracture, but almost no theses study the distribution characteristics and active periods of fractures belong to the eastern belt of Altun Mountains Front. The reasons are that the area is covered by Quaternary strata and the comprehensive evaluation result shows that there have no geological conditions of forming large oil-gas reservoirs. So there is lack of corresponding seismic and non-seismic data.The eastern belt of Altun Mountains Front, refers to the area from the Yueya Mountain to the Lengbei region, lies in the northwest of Qaidam Basin. There has obtained some important breakthrough in natural gas exploration, including achieved industrial gas production in bedrock, J, E1+2 and E3 in Dongping and NiuDong region, discovered various types of reservoirs, such as structural, lithological and structure-lithology types, and meanwhile it has demonstrated that the exploration prospects of the eastern belt of Altun Mountains Front is bright. There has deployed a large number of 2D and 3D seismic and non-seismic exploration and drilled more than 40 exploration and appraisal well, achieved a large number of high quality seismic, non-seismic and drill log data, laid a solid foundation for study the fracture of the Altun Mountains Front by geophysical data.In this paper, the seismic-geological comprehensive study were carried out by means of geological, seismic, non-seismic and well log data, the main research contents and recognition are as follows:(1) On the basis of the structural orientation filter, fine interpretation of seismic data were carried out by use of semblance spectrum and curvature. It makes clear that the fracture on the profile have several combination types, such as hedge, back thrusts back. Y-shaped.etc. Analyzing the distribution characteristics and combination rule of the fracture on the profile combined with ground geological, non-seismic and drilling results. There have two contact relationships which are the fracture and the unconformity between basin and mountain.(2) By analyzing the fault growth index, ancient height of fault and tectonic evolution, it is believed that there have multiple tectonic movements such as late Yanshan movement and Hemalaya movement which formed today's fracture characteristics and tectonic framework.(3) According to the cause of fracture in research area, it can be divided into two kinds which are the east Kunlun compressive system and Altun strike-slip system. On the basis of controlling effects on tectonic and formation, the fractures can be divided into three levels. Among them, the first and the second level fracture mainly controlled the distribution of strata and the formation of the tectonic belt, the third level fractures controlled the formation of local trap.(4) The controlling effects of fracture action to the forming of hydrocarbon source rocks, reservoir and cap rocks, structural trap, stratigraphic trap and to the hydrocarbon migration were analyzed, the hydrocarbon accumulation models were established and the accumulation rules were summarized, which will play a certain guidance and reference to the region's oil and gas exploration.