Study Of Sedimentary Filling Charaters And Structural Controls Of Xingouzui Formation, Jianghan Basin

Jianghan basin is a typical continental rift basin.And Xingouzui formation is an important oil and gas exploration layer.Oil fields are most the structural reservoirs.With oil and gas exploration deepening and transforming,the current targets have been transferred to the lithologic and stratigraphic traps.Therefore,analysising based on sequence stratigraphy,studying sedimentary characters and control factors,predicting the sand bodys distribution have important theoretical and production of means for oil and gas exploration in this basinXingouzui formation in Jianghan Basin has been divided in 4 third order sequences combining outcrop,seismic,logging,core,etc.SQXS corresponds to Xingouzui formation upper and is the region’s seal.And Xingouzui formation lower is divided in 3 third order sequences roughly the same with the oil group and is the main reservoir rocks.River - delta,shallow lake, salt lake,half-deep lake,are main sedimentary systems in this area.Accorded to heavy mineral composition and ZTR characteristics,seismic slices,and other means,Zhijiang,Yuanan,Nanjing, Hanshui,Hanchuan five sediment sources have been identified,which Yuanan and Nanjing advanced flower-like southward into the Jiangling depression and extending to Gongan faults zone, covering a large parts of Jiangling Depression;Hanshui source extends southwest to Xingou area in Qianjiang Depression from Qianbei fault and covered most parts of Qianjiang Depression. Hanchuan source has two branches Mawangmiao and Mianyang,which Mawangmiao advanced southwest and arrived Jianxin area in Qianjiang Depression and encountered with the Hanshui source in the line Ma17-M60X-Ma55-He2.Zhijiang source lied in west of Jiangling Depression also has a certain size.Accordance the relationship with Synsedimentary faults,4 types of structural palaeogeomorphology were identified:①steep slope break belt:control sand distribution by increasing the capacity of space.When there is sufficient supplying source,they become the major sand accumulation sites,and the important area of oil and gas exploration eare.When they are as far away from the source system,their remote often modified by the slope break and developed lake fan.When the source system is not developed,they mainly dominated by muddy sediments. Steep slope break belt can also communicated the sand along and blocked the vertical,forming a long strip sandbody along the steep faults.②slope fault zone:communicating and regulating the water system,,is an important channel sand body.③low uplift block under the water:water bypassing the low uplift block and forming a number of underwater distributary channels around it; also reducing the capacity of space and shallowing water,forming sand beach bar etc.④slope zone:far away from the tectonic faults,the main deposition mudstone,gypsum mudstone.There are Meihuaiqiao,Qianjiang,Mianyang sags which can form hydrocarbon in Jianghan Basin.And long succession positive elements around the sags are favorable structural units for the oil and gas accumulation zones.Combined with the reservoir profile analysis,three favorable oil and gas accumulation zones are recognized:aound Meihuaiqiao-Huduhe incline zone,around Zongkou-Panchang incline zone,around Baimiao incline zone.