| Tangyuan fault depression is a second-order one in the north of Yishu graben. Several evaluation results about the Tangyuan fault depression show a considerable amount of oil and gas resources, but so far, a major breakthrough of geological exploration has not come forth.Based on the re-interpreted seismic data, this paper considers the structural feature of Tangyuan fault depression is mainly the development of NE-striking and NSS-striking fracture, secondly ES-striking and SN- striking fracture nearly. Two group of leading faults make the whole Tangyuan fault depression exhibit west-eastern belted and south-north partitioned structural pattern. Tangyuan fault depression has gone through six tectonic evolution stage: fault depression in Mesozoic, and intense, sustained, fault-concave transformed, atrophic, extinct fault depression in Cenozoic. Through the comprehensive analysis for the data of paleontology, lithology, logging and seism in the study area, the seismic geological position is re-calbrated. By means of the record of well-earthquake synthesis and the strata correlation of leading wells among, the paper divides and correlates the stratum of Tangyuan fault depression, adjusts the original layered data, and then confirms the existence of Cretaceous and Paleocene Wuyun Formation and its general distribution range. Synthesizing the research results of outcrop, core, logging and seism, by the divided method of quartering stepless sequences, the paper establishes the sequence stratigraphic framework of Tangyuan fault depression, and classifies two megasequences, three super sequences, twenty three-order sequences. Through the observation and description of the core drilling, the phase-analysis for the cores are made. At the same time, carrying out the study on the logging and seismic phase, the paper establishes the corresponding relation of seismic and sedimentary facies in the study area, recognizes three main phase types of fan delta facies, lacustrine facies and sublacustrine fan facies, and classifies further seven kinds of sedimentary sub-phases and seventeen kinds of sedimentary micro-phases.Comprehensive study on the character of the source bed, reservoir and cap cover shows, there are two major types of source rocks, which are dark mudstone and coal, mainly to dark mudstone. Through the organic geochemical analysis for the source rocks, it is clear that organic matter type is mainlyⅢtype,ⅡB type partly,ⅡA type individually. The best organic-matter abundance of target bed are Bao No.1 section, Da No.1 section and Wuyun Formation, Xin-Ancun Formation secondly, Bao No.2 section and Cretaceous thirdly. The organic matter maturity becomes big with the increasing depth. According to the tracing contrast of the source rock, lacustrine-facies pelite of Da Lianhe Formation and Xin Ancun Formation is the major types of source rocks of lake oil, while coal measure strata of Xin Ancun Formation and Wuyun Formation is the major types of source rocks of coal oil. The mudstone of Bao Quanling Formation No. one section and Cretaceous is the potential source rock. The reservoir lithology of Tangyuan fault depression are mainly unequal sandstone, hybrid sandstone, sandy conglomerate and lithic arkose, and its physical properties belongs to medium porosity and medium permeability. The source reservoir cap assemblage can be divided into three main types of self-generating and self-accumulating,top reserveior-bottom source,and new-generating and old-accumulating..The total volume of oil resource and gas resource of Tangyuan fault depression are respectively 0.952～2.509×10~8 tons and 469.6×10~8 stere. The resource prospect is considerable. After analyzing comprehensively the geological condition of oil and gas, the paper forecasts the favorable exploration belt and points out the exploration direction of the next step.
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