The Characteristics Of Changtu Fault Depression And Its Oil-gas Distribution

Songnan area in recent years has shown a good momentum of exploration. In recent years, China petroleum and Sinopec concentrate superior power, through the seismic, logging, geological exploration and so many kinds of research methods and carry out large-scale exploration and research work for many fault depression in southern Songliao Basin, they learned a further information about the distribution characteristics, sedimentary background, hydrocarbon generation condition and the reservoir rock characteristics of Songnan area. Petroleum geologists are aware of Songnan area not only Lujiapu fault depression has greater potential for exploration, the eastern Zhangwu fault depression also have same potential for exploration.The comprehensive application of drilling, well logging, core, outcrop and seismic data, researching on the characteristic of Zhangwu fault depression stratigraphic. On the base of research of the stratigraphic characteristics, through the interpretation of 2D seismic data fine structure in the stratum of Zhangwu, clarified the structural features and evolution characteristics of Zhangwu fault depression; Combining with the sedimentary core, single well and well facies, subfacies and microfacies study, determined the basin filling evolution model;Through the integrated use of geochemical data, reservoir physical property data and reservoir description data,we determined the faulted reservoir geological conditions, and on this basis, summarized the characteristic of the distribution of oil and gas. Through careful research, we conclude that:1、In the structural characteristics of Changtu fault: a west east fault super nearly north-south graben as a whole. North to south is shallow, the binary structure on the fault depression". North South differences:North double break two wa folder a long, central and southern fault step long wa structure. Six tectonic units:from north to south is divided into the northern sag, central uplift belt, southern sag belt, South tectonic belt, south area, eastern slope depression zone.2、Controlled by the old tectonic and sedimentary characteristics of tectonic movement, the formation is west and thin, pointed out to the basin edge feature. Due to the western margin of Changtu fault and affect the development of fan deposits, the main source of the northeast to braided river delta injection, lithology shows the characteristics of the Eastern Western coarse fine. And on the nine and V Shahai formation overlying the Temple group showed a micro angular unconformity.3、According to the regional data, summarized the sedimentary cycles and lithology combination, palaeontological assemblage characteristics, symbol layer, seismic reflection characteristics, carried out stratigraphic division and comparison results show that the area of southern Songliao Basin, Changtu depression mainly formed in the Jiufotang formation, lithology of sandstone and mudstone, tuff breccia or volcano, vertical a fining upward sedimentary characteristics mainly, there are differences on different lithology combination plane.4、The research shows that the reservoir deposition is that Changtu fault depression in the south area are concave bidirectional provenance, in the west fault zone, steep slope depth, as the product of rapid accumulation, mainly for coarse sediment, fan delta deposition, mainly including tuffaceous breccia, tuffaceous conglomerate; east slope is relatively slow, the deposition thickness of thin fine granularity. Braided river delta deposition, the rock is mainly fine sandstone, siltstone.5、The Changtu fault depression has a complete source-reservoir-cap combination: it has a set of hydrocarbon source rocks, namely the dark mudstone of Jiufotang formation, there are 2 sets of reservoirs: sandstone mudstone in Jiufotang formation, sandstone and conglomerate in Shahai formation. From the longitudinal and transverse, we distinguish three types of effective reservoir combination: self-generation and self- reservoiring type, lower-generation and upper- reservoiring type, upper- generation and lower- reservoiring type.6、Changtu formation developed dark mudstone in Zhangwu fault depression, to be the mian hydrocarbon source rocks. that is dark mudstone of Jiufotang formation, it develops two sets of reservoir, Shahai formation and Fuxin formation of the Lower Cretaceous，the type of the source rock is the dark mudstone, carbonaceous mudstone and coal and a small amount of oil shale. The hydrocarbon source rocks mainly developed in the upper part of the templeof the Jiufotang formation.7、In terms of oil-gas distribution pattern:according to the development of the source rocks in the south part of Songliao Basin, combined with the organic enrichment, type of organic and thermal evolution stages of organic, on the vertical, Jiufotang formation is the best, followed by Shahai formation. On the plane, Changtu fault depression is best, followed by Daleng, Manghan. Among them, Changtu faulted Jiufotang formation of Changtu faulted had four hydrocarbon generation center, in the southern sag belt quan 1 well area in the southern sag belt is most favorable;...