Translation Features On Second Segment Of Shuangyang Formation Of Moliqing Fault Depression, Yitong Basin

Yitong Basin is the Southern Section of Jia-yi Graben System which belongs to the Northern section of Tanlu Fracture, and it's also a mainstay in the Hercynian folded basement up on the development of oil and gas Paleogene strike-slip fault basin, more than 160 km from north to south wide, 10 ~ 20km range, an area of about 2400km2. Moliqing Fault Depression is the secondary structural unite of the Southernmost of Yitong Basin, the northwest boundary is nearly vertical shape key faults in the edge, is a narrow half-graben basins which include a lot of faults. The Fault Depression has development the Eocene period of the Shuangyang group,sheling group,Yongji Group, the Oligocene of Wanchang group,Qijia group, the Neogene of chaluhe group and Quaternary. The research layers are five sand group of second segment of Shuangyang Formation, the main purpose is to find out the translation features characteristics of the Sand group and translation evolution ,in order to make the next deployment of oil exploration in the future to provide a reference.Yitong basin has a complex structure, subject to many changes in the regional stress field and also under the control of two times reverse translation in Tan-Lu fault, that made the sand body of fan delta and the Lake floor fan have a complex development, the characteristics of the lithologic aspect to change quickly in vertical, the oil distribution in space instability.For the above reasons carried out in this paper, of depositional systems,we establish the deposition mode with application of lithologic character and new theory which carried out Sedimentary facies and translation features of every sand group of second segment of shuangyang formation. combined with the historical background of fault development in the region, we analysis the evolution of sand group overlapped rules.The sedimentary facies in this paper contains three kinds of types: fan delta, lakes and sublacustrine fan phase. We also made a further divided into eight kinds of sedimentary facies, 17 kinds of microfacies. Lakes in the region has development of various periods, the lakes can be identifed with shallow lake facies,and deep lake facies. The former is mainly distributed in the east and southwest, The deep lake facies are widely distributed in the east and west. The district found a number of sublacustrine fan, sublacustrine fan further classify into inner fan, middle fan and outer fan facies. Fan delta facies development in this area, and mainly distributed in the northwestern margin of Moliqing depression. Fan delta can be divided into fan delta plain, fan delta front and prodelta. In order to study characteristics of sedimentary facies, this recovery of sedimentary facies further fan delta front can be divided into inner edge of fan delta front, outer edge of fan delta front. Among them, the inner edge of fan delta front is radial flow with in the role of a strong underwater distributary channel and mouth bar area mainly contain coarse clastic sediments; outer edge of fan delta front is radial flow outside the role of weak, a strong sand sheet deposition with the role of the lake water.Yitong Basin Northwest controlling faults change from the dextral transtensional movements in Eocene to Oligocene sinistral pressure torsion, so the sand body and facies of five sand group has translation dislocation. In early Eocene, because of the dextral shearing of the controlling faults, five sand Followed by deposits, and associated with dextral strike-slip fault occurred and five sand group to one group to slip away in turn decreases. In late Eocene, the basin evolution changed into the thermal subsidence, Dextral transtensional ended, under the control of thermal subsidence,the basin entered into the overall slow down. Since the early Oligocene, due to changes of the regional tectonic stress field, the regional tectonic stress field to the Transtension from the Extrusion twist, the basin has occurred sinistral strike-slip movement, 1-3 Sand Sections show a reverse translation dislocation, the performance of the L-shift, and the sliding distance decreases, fourth sand group and fifth sand groups still have a right hand Translation, but declined to slip away.