Tectonic Restoration And The Formation Structural Analysis In The Potential Zone Of Gas Hydrate Of Qiongdongnan Basin

South China Sea is one of the most famous marginal sea of Pacific Ocean in thewest, located in the convergent hinge of European-Asia plate,Pacific plate andIndia-Australia plate in regional tectonics. Qiongdongnan basin is a Tertiary basindeveloped on the NW continental margin of the South China Sea. Hainan IslandUplift zone is to the north of Qiongdongnan basin. Yinggehai basin is located to thewest of it, Shenhu-Ansha Uplift zone and Xisha Trough basin is to the east of it. XishaIslands and Zhongjiannan basin is to the south of it. It is an important enriched oil&gas zone, a potential zone of gas hydrate too. It consists of shelf area, slope area,Central Depression Belt and South Fault Bench Belt.In this paper, part of 4 seismic profiles in Qiongdongnan basin was restored by2DMove software. We calculated the extension parameters of every balancedcross-section in the different period, quantitatively analyzed the intensity of tectonicevolution in the study area, expatiated the tectonic evolution history of Qiongdongnanbasin, and primarily discussed the relationship between the formation of gas hydrateand the tectonic evolution. Simultaneously, on the basis of the geological conditionanalysis of gas hydrate formation and the interpretation results of high resolutionseismic data, we discussed the structural accumulation of gas hydrate in the differentpart of the study area. According to our analyzing, we obtained the followingconclusion:We identified 27 mud diapirs in the study area totally. There are 12 mud diapirsto be found in the distributed area of BSRs. The mud diapirs mostly developed belowthe reflecting boundary T5, were identified in the every structural unit ofQiongdongnan basin. According to the total extension parameters of balancedcross-section, the tectonic movement of Qiongdongnan basin is active in OligoceneEpoch(E3), but it becomes more inactive than ever since Early-Middle Miocene.Qiongdongnan basin has two phase of tectonic evolvement which are fault depressionand depression. The basin shows a double-layer vertical structure with faultingstructures in the lower and depressing structure in the upper sector. The lower andupper structural sector can be identified by the rifting unconformity surface T5 inQiongdongnan basin. They represent respectively the fault depression in the early andthe depression in the late. Analyzing the structural condition of gas hydrate formation,we can conclude that, mud diapir structures are the primary mode of gas hydrateaccumulation in Central Depression Belt;faults are the primary mode in South FaultBench Belt.