Study On The Mixed Rock Microenvironment Of Lucaogou Formation In Jimusar Depression

Jimusar Depression is located in the southwest of the eastern uplift of Junggar Basin.At present,the most important oil-bearing blocks of Lucaogou Formation in the research area are all located in Jimusar Depression,which is administrativly belonging to Jimusar county of Xinjiang uygur autonomous region.Jimusar Depression had experienced Hercynian,Indosinian,Yanshan and Himalayan multiphase tectonic movement,bottom-up development of Carboniferous,Permian,Triassic and Jurassic,Cretaceous and paleogene,Neogene and Fourth system,the Permian can be divided into three groups,from bottom to top respectively are well Jingjingzigou group,Lucaogou group and Wutong ditch.The Lucaogou Formation is fully sag developed,with the characteristics of sour-reservoir adjacent and near-source accumulation.It is one of the important oil-bearing strata in the eastern Junggar Basin.Lucaogou in recent years,the focus of the composition of shale oil and gas exploration blocks,but the data constraints,the sedimentary microfacies in the study area distribution characteristics of the study did not go deep into the microfacies of stage,the evolution law of the research is not comprehensive,how to develop under the various time base-level cycle control Salinized lake facies-delta facies mixing product fine grained rock distribution research there is a big difficulty.Furthermore,the study on the sedimentary environment and its controlling factors of mixed fine grained rocks is relatively weak,and the study on the microenvironment of mixed fine grained rocks is just beginning.Therefore,it is of great theoretical and practical significance for shale oil exploration and development to study the distribution characteristics and evolution rules of sedimentary microfacies of mixed rocks in the study area,as well as the main controlling factors of mixed rock microenvironment.Based on core,thin section,scanning electron microscopy?sem?,logging curve,XRF,XRD data,combined with core facies analysis,combination and least squares fitting of logging curve and 3 d lithology random simulation technology,such as using the high resolution sequence stratigraphy,petrology,sedimentology,element geochemistry related theory,carried out under the high resolution sequence stratigraphy framework control level of small layers of sedimentary microfacies study,the study area is established mixed fine grained rock sedimentary microfacies model,comprehensive analysis of the dessert interval peperite sedimentary environment and its control factors,and established the comprehensive model of elemental-mineral-lithologic-sedimentary microfacies.Research shows that:?1?the Lucaogou Formation can be divided into 5 medium-term cycles,9 short-term cycles and 33 ultra-short-term cycles.The intermediate cycle corresponds to the level of the segment,the short-term cycle is equivalent to a sand group or a small layer?including multiple single sand layers?,and the super-short-term cycle corresponds to a single layer.?2?Lucaogou Formation is a set of mixed fine grain rocks composed of fine clastic rocks,carbonate rocks and mudstones.It is a set of saline lake-delta sedimentary system.The types of sedimentary microfacies in reservoir are identified,which mainly include sand dam,front delta mud,sand bank,mixed bank,dolomitic flat and lacustrine mud.?3?Dessert segments of Lucaogou Formation were mainly distributed in upper P₂l₂²and upper P₂l₁²segments.The sedimentary model of terrigenous clastic-carbonate mixed fine grained rock in the target stratum of the study area is put forward.?4?The change of the sedimentary microenvironment of Lucaogou Formation has a certain influence on the dessert layer.The upper dessert layer has a relatively humid climate,higher salinity,stronger reducing property and deeper water.The climate of the next dessert is relatively hot and dry,with less salinity,weak reducibility,oxygen-rich and shallow water.?5?The relationship of mutual restriction between sedimentary microfacies and sedimentary microenvironment is discussed,and the comprehensive model of element-mineral-lithology-sedimentary microfacies is established.When the climate is drier,the salinity is at medium and low level,the precipitation is not enough,and the water depth is shallow,the development of fine sand rock,feldspar litharenite,dolomitic siltstone,more conducive to the deposition of sand dam,sand beach,mixed bank microfacies,among which,mixed bank deposition,the ancient productivity or the best,the upper dessert layer is very obvious.When the climate is relatively humid,the salinity is high,the precipitation is abundant and the water depth is deep,the silty dolomite,micritic dolomite and lacustrine mud are mostly developed,which is more conducive to the deposition of shallow lake-semi-deep lake dolomitic flat and lacustrine mudstone.