The Restoration Of Tectonic-Deposition Pattern And Evaluation Of The Hydrocarbon Source Rock In The Late Triassic Western Ordos Region

The western Ordos Region is situated in the South-North trending structural zone which lies between pacific ocean tectonic domain and Tethyan tectonic domain. It is surrounded by different tectonic units of the north china craton,alxa block, the qin-qi orogen.Different structure stage, along with different structure system and their compound, these make the structure of the area complex and different section have different structure in same structural stage since Late Triassic.Also these makes the study of structural formation and evolution quite difficult, which restricts the evaluation of the oil prospect since Late Triassic.especially there's great disagreement on the structural attribute.The key to solve these problem is to restore the tectonic-Deposition pattern of the period and ensure the structural attribute. Meanwhile, as one of the three hydrocarbon source rock layer, Upper Triassic serie is a key horizon for oil-gas exploration in the western Ordos Region, so the hydrocarbon source rock evaluation is necessity.By collecting a large number of samples of Upper Triassic serie in person, and analysis them with modern machine and method, mainly do the working below:①Analysis the paleocurrent ;②Analysis the gravel component of the conglomerate;③Analysis the component of the sandstone;④Analysis The zircon by LA-ICP-MS U-Pb method ;⑤on the basis of these, analysis the provenance of the area in all;⑥Associate with the structure background, using geochemistry information, analysis the structural attribute and sedimentary- structure pattern of the area;⑦By thermal simulation experiment, Recover and revise the TOC and S1+S2 this area;⑧By the research former people has done, considering the reality of the research area, establish the lower limit of abundance of the organic matter and evaluate them.The achievement are below:1,Alaxa in the northwest and the west of the basin and the qilian-qinling orogenic belt in the southwest are the provenance of the area in late Triassic2,The pattern of the western Ordos Region in the late Triassic is: The north edge is to the yinshan uplift, south and southwest edge is to the qinling-qilian uplift, east edge is to the Ordos basin, The west edge is to the line of lingwu-weizhou-pingliang-longxian.In the late Triassic, Ordos basin and Helanshan are two independent basin, the west edge of Ordos basin is a craton basin which formed under pressing background, and Helanshan is a faulted basin3,The analysis of the Hydrocarbon of Upper Triassic serie indicate: the abundence of organic matter is good, The type of the organic matter is mainly II_A and II_B, I and III is quite a few.The maturity of organic matter is high.