Evaluation Of Subsalt Accumulation Conditions Of Cambrian In Keping Thrust Belt, Tarim Basin

Marine carbonate reservoirs in Tarim Basin have great potential for oil and gas resources.In the middle and Upper Cambrian of Tarim Basin,there are stable and continuous gypsum rocks as the good cap rocks.Therefore,the Cambrian salt source rocks and reservoirs are the focus of the study.There are some disputes over whether the carbonate source rocks from the Tarim Basin is from the Cambrian or Ordovician,especially for the hydrocarbon generation potential under the Cambrian salt source rock.The discovery of the industrial oil and gas flow in the middle and lower Cambrian dolomite reservoirs in the Tazhong area further confirms that the Cambrian reservoir in the Tarim Basin has a good reservoir property potential.However,the study of sub salt source reservoir in the area of the Tarim Basin is relatively shallow.There are few data on gravity,magnetic,electric,seismic and drilling data in the study area.Through the study of the predecessors' data of the colping area in the Tarim Basin,this paper carries out the field geological survey and sampling,combined with the data of drilling,and analyses the source reservoir characteristics of the Cambrian in the study area: two sets of two types of hydrocarbon source rocks are developed under the Cambrian salt system in the Tarim Basin,the shale of the yyers and the shale of the lower part of the Shaw Braque formation and the yillus.The main type of organic matter is type I,which is considered as a good source rock.The type of organic matter in the lower part of the Shaw Braque group is partial I-II and is in the high maturity stage.The source rocks of the lower part of the shaoxer Braque group are mainly planktonic algae,containing a small amount of benthic algae fragments,and the sedimentary period is in the reduction of oxygen-oxygen reduction environment,the later stage of regression,and sea level.The lower part of the paleo productivity is higher than the upper part of the paleo productivity;the big set of dolomite in the upper part of the Shaw Braque formation is the main reservoir,and the part of the formation of the rock type is mainly granular dolomite and all kinds of crystalline dolomite.The type of the reservoir space is mainly dissolved pore,algal frame and crack,and the porosity and permeability of the stromal dolomite reservoir.The rate is relatively low,and the formation of high-quality reservoirs is mainly dependent on the transformation of late constructive diagenesis.