Study Of Sedimentary Facies And Source Rock's Distribution Of Cambrian,Tarim Basin

The study area of this paper is Tarim Basin.The target layer is Cambrian.Based on the present exploration situation of the study area and previous research results,theoretical direction of architectonic geology,sedimentary petrography,logging geology,paleontology,seismic stratigraphy and the like are applied to make comprehensive research.On the basis of regional geological background,making an analysis of the drilling,logging and seismic data,results of thin section identification and rock core observation are utilized to study the petrological and sedimentological features of this area deeply.Combining drilling data with seismic one,the formation characteristic is then recognized.From point and line to plane,the research is made to make sure the distribution and evolution of the sedimentary facies,and then to set up the sedimentary model.The distributon of source rocks is then studied finally.Tarim Basin developed from Sinian basement.It experienced the first stage of early Caledonian Movement and the second stage.During the Cambrian,it experienced the process from stretching to compression.The first stage of early Caledonian Movement,which occurred in the late Sinian period,caused most areas of the basin uplifted and exposed.In this way,there was an unconformity surface between Sinian and Cambrian system.Sedimentary discontinuity and karst development on top of Cambrian could be seen everywhere in Tarim Basin,which were caused by the second stage of early Caledonian Movement.During this period,Tarim Basin was mainly in an extensional environment.The decline of global sea level was the main factor causing the platform to be exposed and denuded.Due to the act of the second stage of early Caledonian Movement,the influence of the continuous tension led to a series of extensional active faults in Tarim basin,and caused normal fault stretching settlement in Tazhong.Regional uplift and fold occurred in part of Bachu area.Then Hetian palaeohigh arised.There's a great difference between the lithostratigraphy of west and south area in Tarim Basin.Cambrian in Keping-Bamai-Tazhong-Tabei area developed Yuertusi Formation,Xiaoerbulake Formation,Wusonggeer Formation,Shayilike Formation,Awatage Formaion and Xiaqiulitage Formation.Cambrian in Manjiaer depression-Kuluketage area developed Xishanbulake Formation,Xidashan Formation,Moheershan Formation and Tuershaketage Formation.During the Cambrian,Tarim Basin was stable sedimentary of carbonate platform among the craton.Through a combination of lithology,logging response and seismic facies identification,8 sedimentary facies existed in the area: the coast,evaporation platform,restricted platform,open platform,platform margin,marginal slope,continental shelf and basin.What's more,in southern part of the platform,Yuertusi Formation mainly developed littoral facies,Xiaoerbulake Formation developed restricted platform.Wusonggeer Formation developed evaporation platform,Shayilike Formation developed open platform,Awatage Formation developed evaporation platform,Xiaqiulitage Formation developed restricted platform.However,evaporation platform did not exist in northern part of the platform.It's hunger basin in the east of Tarim basin.Between both of them,there're slope and continental shelf.Cambrian source rocks of Tarim Basin were divided into two types,argillaceous source rocks and carbonate source rocks.They were obviously controlled by sedimentary facies,argillaceous source rocks developed in shelf-basin facies zone,carbonate source rocks developed in platform facies zone.Cambrian source rocks of Tarim Basin were widely distributed,developed in the southwest and northeast shelf-basin facies zone of the basin.In the southwest of the basin,Cambrian argillaceous source rocks distributed in Kashgar-Yecheng Depression-Tanggubasi Sag shelf facies zone,with a great thickness and decreased eastward.In the northeast of the basin,Cambrian argillaceous source rocks distributed in Aksu-Shaya Uplift-Shuntuoguole Uplift-Manjiaer Depression-Kongquehe Slope-Guchengxu Uuplift shelf-basin facies zone.In Manjiaer Depression-Kongquehe Slope-Guchengxu Uuplift,the thickness increased from west to east.In Aksu-North Tarim-Shuntuoguole Uplift area,only Yuertusi Formation of Cambrian got hydrocarbon generation potential,the potential was the greatest even though the thickness was small.The distribution range of standard carbonate hydrocarbon source rocks in Cambrian of Tarim Basin was small,locally developed in platform facies area of the western basin.A small range distributed in the west of Bachu Uplift near Tong 1 Well;in the center of Bachu Uplift,Fang 1 Well-Hetan 1 Well-He 4 Well also developed standard carbonate hydrocarbon source rocks.