Study On Triassic Sedimentary Facies And Lithologic Traps In Shunbei Area Of Tarim Basin

On the basis of previous research results,under the guidance of sedimentary geology,logging geology and geophysics theory,the Triassic system in the Shunbei area of the Tarim Basin was studied,this paper makes full use of drilling core,logging,seismic and testing auxiliary data,on the basis of unified stratigraphic division.The characteristics and evolution of Triassic sedimentary facies in Shunbei area are studied,and analyzed the characteristics of lithologic trap development.The following results have been recognized:On the basis of stratigraphic division and characteristics of single wells,well-seismic calibration studies were carried out.The correspondence between seismic interfaces and stratigraphic interfaces is good:T5⁰ is the bottom boundary of the Triassic system,T4⁷ is the top boundary of the Ketuer Formation,T4⁸ It is the top boundary of the lower section of the Akkule Formation,T4^6a is the top boundary of the Akkule Formation,and T4⁶ is the top boundary of the Halahatang Formation.Based on the single-well stratigraphic division and the combination of well-seismic stratigraphic comparison,the study of the stratum plane distribution law of each section of the Triassic system was carried out.Based on the observation and description of drilling core,combined with indoor test and analysis,the Triassic strata in Shunbei area are divided into two types of sedimentary facies:delta and lake,based on the analysis of color,lithology,sedimentary structure,log facies and seismic equivalent sedimentary identification marks of Triassic rocks in Shunbei area.The subphase of the delta front can identify the underwater distributary channel,the distributary bay,the estuarine dam,the underwater natural embankment slightly equal,and the coastal shallow lake subphase can be divided into the shore shallow lake sand dam and the shore shallow lake mud microphase.On the basis of the classification of the above sedimentary microfacies types,the development characteristics of various sedimentary microfacies are studied.Based on the study of sedimentary background of Triassic region in Tarim Basin,the plane distribution and evolution of sedimentary facies in different period of Triassic in Shunbei region were systematically studied by compiling the contour map of sand body and sand-soil ratio and combining the analysis of dominant facies in single well.Sedimentary facies distribution is affected by the provenance of the northern Shaya uplift,the direction of the underwater distributary channel in the leading edge of the delta is from north to south,and the delta front and the shallow lake have undergone several periods of alternating evolution.at the same time,affected by the supply degree of the source of the Shaya uplift,the development scale of the vertical up-down underwater distributary channel has the characteristics of weak?Kothur Group?-strong?Akkul Group?-weak?Harahatang Group?evolution.According to the provenance,sedimentary facies distribution and evolution rules,the Triassic delta-lake deposition model in the Shunbei area was established.Based on the above research results,the present structural characteristics,sedimentary microfacies types,faults and reservoir cap assemblages are analyzed,and the Triassic in Shunbei area is divided into three types of lithologic traps:sedimentary traps,fault-controlled traps and composite traps.All kinds of lithologic traps have a good relationship between reservoir and cap combination.The lithologic traps of the shore shallow lake mud controlled by normal faults and the up-dip lithologic traps are favorable exploration directions in the Shunbei area.