Diagenetic Features Of Jurassic Reservoir And Their Implications For Reservior In Moxizhuang-yongjin Area Of Junggar Basin

There are abundant oil and gas reserves in Junggar basin.The Moxizhuang-Yongjin area is located in the Well Pen-1 West sag and the north slope area of Changji sag on the west side of the hinterland of Junggar basin,and the Jurassic reservoir is the key exploration horizon.From macroscopic and microscopic two angles,based on the observation of underground cores in Shawodi,Moxizhuang,zhengshacun and Yongjin areas,this thesis studied the characteristics of petrology,physical properties,pore structure and diagenesis of sandstone reservoirs in Shawodi,Moxizhuang and zhengshacun Jurassic Sangonghe Formation and Xishanyao Formation in Yongjin area,by means of scanning electron microscope,electron microprobe,cathodoluminescence and X-ray diffraction.On this basis,the influence of diagenesis on the reservoir is carefully analyzed,and the following understandings are obtained:(1)The braided river delta deposits are mainly developed in the study area,which can be divided into three subfacies: braided river delta plain,braided river delta front and pre braided river delta;The lithology is mainly sandstone,with a small amount of conglomerate and mudstone;the sandstone is mainly medium sandstone and fine sandstone,followed by siltstone and coarse sandstone;The main types of sandstone are feldspar lithic sandstone and lithic sandstone,with less lithic feldspar sandstone.(2)The pore types in the study area are primary pores,intergranular dissolved pores,intragranular dissolved pores,intercrystalline pores and microfractures,etc.The physical properties of the study area are diverse.Sangonghe Formation belongs to low porosity and low permeability reservoir,while Xishanyao Formation belongs to ultra-low porosity and ultra-low permeability tight reservoir.The pore throat types of Shawodi and Moxizhuang are mainly small pore throat and narrow pore throat,while those of zhengshacun and Yongjin are mainly flaky and curved flaky throat.(3)The diagenetic stage of Sangonghe Formation in Shawodi,Moxizhuang and zhengshacun areas is middle diagenetic stage A(organic matter is in low mature stage).Most of the diagenetic stages of Xishanyao Formation in Yongjin area are in middle diagenetic stage A,and some wells are deeply buried in middle diagenetic stage B(organic matter is in mature high mature stage).(4)The main diagenesis in the study area are compaction,cementation,dissolution and metasomatism,which have a good control on the pore distribution and reservoir performance.The compaction in the four areas is obviously different,and the compaction is gradually strengthened with the depth;the cementation is strong,mainly carbonate cementation,followed by siliceous cementation and clay mineral cementation;the dissolution is generally developed,but not strong in the whole area,mainly feldspar particles and volcanic rock debris.