Research Of Sedimental Facies Of The Permian Wutonggou Formation In The No.7Area Of Jimusaer Depression Of Junggar Basin

The NO.7area is located in the north about7.5kilometres of Jimusaer Depression, xinjiang,it’s53.4kilometres from the north part of NO.16area in the northwestern of Santai oilfiled.Its structure is in the east slope of Jimesaer Depression of Junggar Basin,the characteristic of structure is complex,and it’s comes through Haixi、Yingzhi、 Yanshan、Ximalaya and so on many tectonic movement successively.There are so many ruptures,to form Houbaoz、Ji003、Ji007、Ji7rupture,is typical of lithologic-structure oil reservoir.Predecessors have done the research work at different levels about Permian stratigraphic division and sedimentary reservoirs、oil and gas exploration targets forming conditions in the Permian WuTongGou formation of Jimusaer Depression of Junggar Basin and made many achievements and understanding, but there are different understanding about the sedimentary facies study area, distribution and sequence stratigraphy and so on.Based on the core observation,and combined with using single well of the sedimentary facies、drillling lithologic section、the characteristics of electrical and so much geological materials,to the characteristics of sedimental facies of secondary interval of the Permian in the NO.7area of Jimusaer Depression of Junggar Basin. Through analysis and study, the area of the secondary interval Wutong formation is not only a set of fan-delta system,but also a set of braid river-delta, identified two sub-phase and14micro facies.According to seismic data、drilling data and so on, the formation in the Ji7area from bottom to top are Permian Jiangjunmiao formation (P2j)、Pingdiquan formation (P2p)、Wutonggou formation (P3wt), Jurassic Badaowan formation (J1b)、Sangonghe formation (J1s)、Xishanyao formation (J2x)、Toutunhe formation (J2t), Paleogene System(E), Neogene(N) and Quaternary(Qd). There is no Tertiary、upper Jurassic and Cretaceous strata in Ji7wells block, and the stratigraphic contact relationship between Wutonggou formation、lower Badaowan formation and upper Pingdiquan formation is unconformity. From the bottom upward top Wutonggou formation is divided into two members:P3wt1and P3wt2,P3Wt2can be divided into two sand sets:P3wt21、P3wt22, P3Wt21is mainly a big set of dark grey and grey biack clay sands as pro-delta deposits,then P3wt22and P3wt11are major reservoir.Through studies of single well facies、section facies and plane facies, results showed that the Wutonggou formation sedimentary period, the deposition evolution rule of deposition micro facies is more obvious in spatial and time:P3wt2formation:The thickness of sandstone is between in15.6kilometres to79.3kilometres,the average of thickness is51kilometres,the most thickness is located in Ji008Well. The general trend of sandstone’s thickness is thick of the southeast,to the northwest and both sides become thinner gradually.Sand to than is between in15.6%to 90.9%,the average of thickness is49%,and the maximum located at Ji008Well,the changing trends of the sand then to and sandstone thickness are both same.In the P3wt2period, sedimentary microfacies mainly were underwater distributary channel, bay mud between distributary channels ranked.and to the evolution of river basin being mouth bar sands, far bar sands and prodelta mud.P3swt1formation:The thickness of sandstone is between in14.57kilometres to175.75kilo metres,the average of thickness is80.8kilometres,the most thickness is located in Ji7Well.The general trend of sandstone’s thickness is thick of the central,to the northwest and both sides become thinner gradually.Sand to than is between in58.15%to98.96%,the average of thickness is83.3%, and the maximum located at Ji005Well,the changing trends of the sand then to and sandstone thickness are both same.In the P3wt1period, sedimentary microfacies mainly were underwater distributary channel, bay mud between distributary channels ranked,to the evolution of river basin being mouth bar sands, far bar sands and prodelta mud.P3wt22formation:The thickness of sandstone is between in9.3kilometres to58.9kilometres,the average of thickness is33.9kilometres,the most thickness is located in Ji008Well. The general trend of sandstone’s thickness is thick of the southeast,to the northwest and both sides become thinner gradually.Sand to than is between in19%to100%,the average of thickness is60.2%,and the maximum located at Ji008Well,the changing trends of the sand then to and sandstone thickness are both same.In the P3wt22period, sedimentary microfacies mainly were underwater distributary channel, bay mud between distributary channels ranked,and the scale of underwater distributary channel is bigger than P3wt21period, to the evolution of river basin being mouth bar sands, far bar sands and prodelta mud.P3wt11formation:The thickness of sandstone is between in11.8kilometres to42.7kilometres,the average of thickness is26.1kilometres,and the Ji006well、Ji8well、 Ji9well having more thickness of sandstone than the other well,but the most thickness is located in Ji8Well. Sand to than is between in16.3%to95.3%,the average of thickness is73.3%,and having the high value in Ji010well、J1012well、Ji011well and Ji006well,but the maximum located at nearly Ji010Well and J1012Well.There were developed two underwater distributary channel,the one going through nearly Ji005well、 Ji006well,the other one going through nearly Ji005well、Ji006well,to the evolution of river basin being mouth bar sands, far bar sands and prodelta mud.Base on analysis of the spatial distribution of sedimentary facies, the braid river-delta evolution model is established in the Ji7well area. The first sedimentary period of the member two of Wutonggou was the process of retro gradation when lake level rised, the grain of sediment is fining upward, and the thickness of sediment is thinning upward; the secondary sedimentary period of the member two of Wutonggou was the process of progradation when lake level falled, the grain of sediment is coarsening upward, and the thickness of sediment is thickening upward.Reservoir fault zone of Ji7WellZone is mainly distributed in conglomerate、 glutenite and sandstone(mainly for the medium and thin sandstone),and the oil and gas distribution of sedimentary micro facies are mainly for underwater distributary channel and mouth bar sands.By research group study of Permian Wutonggou group,the Understanding and conclusions are as follows:1、According to the lothological characteristic, the Wutonggou Formation from bottom to top will be divided into two sand groups and four stratums, and P3wt2period is the main oil section.2、The goal formation of Ji7Well area is the braided river delta, but not fan delta. Obviously there are delta front and pro-delta two subfacies, and5microfacies which are underwater distributary channel, bay mud between distributary channels ranked, mouth bar sands, far bar sands and prodelta mud,and underwater distributary channel is the main face of microfacies.3、The source of the Permian Wutonggou formation in the NO.7area comes from the northeast and the southeast.4、In vertical, underwater distributary channel sand lateral migrate deposition frequently,causing more sand body overlapping, presenting thinning upper by a single sand body,making the ideal place oil and gas storage.5、Because of underwater distributary channel sand lateral migrating deposition to adding up into the integrated cross bedding,it can be used for the main identification of the braided river delta.