Research On Depositional Facies Of The Middle Jurassic Shaximiao Formation In Majing-shifang Area, Western Sichuan Depression

The western Sichuan exploration in shallow oil and gas exploration began in theforties of the last century, after60years of exploration and development, theresources to succeed in the critical period.Western Sichuan Depression Shaximiao gas reservoir is typical of tightsandstone gas reservoirs, at the same time it is important natural gas reservoir andproduction layer. The study petroleum geology, sedimentology, sequence stratigraphytheory as a guide, combined with the results of previous studies on the basis ofsequence stratigraphy of the Western Sichuan Depression Majing-ShifangShaximiaostudy area the deposition of Shaximiao phase further analysis anddiscussion. The main access to knowledge and innovative results are as follows:1Sequence stratigraphic analysis: the study area Shaximiao divided twolong-term (SQ1~SQ2) cycles and six medium-term (MSQ1~MSQ6) cyclicsequence. According to the causes of high resolution sequence stratigraphy thestratigraphic correlation rules and methods, a single well in the study area division ofthe short-term cycles, divided into12short-term cycles, corresponding to12Shaximiao sand group.2Provenance analysis indicates that under Shaximiao sandstone to multipleprovenance Western Mountains, Northern, North Eastern, Western SichuanDepression internal mainly affected by the impact of the North, North Eastprovenance Chongzhou, Pi provenance fromthe central Longmen Dayi, poly source;the on Shaximiao deposition period exists to multiple provenance, North West, West,North and North East Western Sichuan Depression main provenance from the north and north east direction.3Sedimentary facies analysis indicates that study area Shaximiao sandstonemeandering river delta deposition, the main sub-phase delta the former Deltasubphase. Main microfacies distributary channel and Underwater distributary Bay.4Petrological characteristics analysis showed that the JS1sandstone usuallyfine-grained, with a high quartz content of cuttings and lower feldspar, the JS2sandstone with high feldspar content, mainly for of sandstone. Shaximiao sandstonecomponent with other large regional differences, with lower quartz and feldsparcontent, the content of carbonate cements are relatively low.Wenjiang feldspar contentis significantly lower than other regions, mainly lithic sandstone. Overall, Shaximiaopetrological characteristics associated with Provenance.5The property analysis studies have shown-low porosity and low-especiallylow permeability characteristics. Shaximiao gas reservoir is typical of tight sandstonegas reservoirs. On this basis, Majing area Shaximiao reservoir properties wereanalyzed and compared,the best distributed in the JS31sandgroup.6Finally, Determine the mode of predicting favorable facies,and the JS31is thefavorable facies.That is based on the study of sequence stratigraphic analysis andsedimentary facies analysis and reservoir Characteristics, combined with the actualdrilling data seismic data.