Sedimentar & Reservoir Under The Framework Of High-resolution Sequence

On the basis of core,logging,seismic,and outcrop data,with the applying of sequence stratigraphy,sedimentology,reservoir geology Synthetically,we carried on the study of deposit system and reservoir characteristics in the Da'anzhai interval of the lower Jurrassic Ziliujing Formation in the middle of Sichuan basin.Based on the theory of high-resolution sequence stratigraphy,a whole deposit cycle is comprised of a up-cycle and a down-cycle,and one stratum can be divided into some short-term,mid-term,or long-term cycles for correlation.Da'anzhai interval is a long-term cycle,which is a third sequence,can be divided into three mid-term cycle,are equal to three fourth sequence:SSQ1?SSQ2?SSQ3.SSQ1 is equal to Dayi section,SSQ2 seems to Daer section,and SSQ3 is equal to Dasan section.After single well sequence division,we correlate the sequence divison between wells,and established a sequence succession frame,which covers the whole study field,and supplies a time scale for afterward discussion.In the period of Da'anzhai interval,Sichuan basin is growing as it's largest stage,with the short source supply and warm climate,pretty much shell limestone had deposited in it,which is the main pay bed in Jurrassic.Based on the lithofacies and lithofacies assemblage and some paleontology evidences,this paper divided lacustrine facies of Da'anzhai interval in middle of Sichuan basin into lakeshore subfacies,shallow lake subfacies and semi-deep lake subfacies.With a range of evidences,including strtum thickness and limestone thickness,combined with sedimentary facies analysis of single well,we completed sedimentary facies figures for three forth-sequence,and discussed the distribution of sedimentary facies for each of them.Based on the distribution of sedimentary facies,distribution range and thickness of limestone shell shoal which is the main reservoir of Da'anzhai interval is described detailedly.Multilevel pore throat has developed in reservoir,and matrix is dominated with micro-nanometer pore throat,most radiuses of pore throat are between 20?200 nanometer,and the filling floor radius of tight oil from experiment is between 22?29 nanometer,therefore,most of pore throats are filled with oil in theory.Additionally,fracture in the reservoir grows widely,and pores and fractures make this reservoir rich and high-productivity.