Reservior Characteristics Study Of Chang2-chang4+5of Yanchang Formation In Zhiluo Oilfield

Zhiluo Oilfield located in the structural unit in middle of Northern Shaanxi Slope,OrdosBasin.The early exploration and development indicated the poor physical property of thereservoir of Yanchang Formation in this area and the distribution of oil and gas controlled bythe factors of sedimentary facies, diagenesis, reservoir properties and so on. In response to thissituation, the thesis is guided by sedimentary petrology, reservoir geology, petroleum geology,geophysical well logging and other related theory,rely on the current advanced experimentaltesting methods,use the information of geological outcrops, drilling, logging, adopt theresearch methods of combining macro and micro, we conduct a detailed study on the reservoircharacteristics of Chang2~Chang4+5of Yanchang formation in Zhiluo Oilfield.Comprehensive studies suggest that regional tectonic is relatively flat, there are some lowand the nose-shaped bulge,the formation thickness are more steady and changedlittle.Provenance is mainly from the North East region,each period the river have NE-SWtrending features,Chang2,Cahng3develope delta front sediments, Chang4+5develop shallowlake sediments,the sand of Chang2developed well.Chang2~Chang4+5reservoir sandstonesare mainly lithic feldspathic sandstone and feldspathic sandstone, the detrital compositions aremainly of quartz, feldspar, debris, mica and so on,the content of interstitial materialcomponent is relatively high,most of cements are chlorite film.Sandstone compositionalmaturity is relatively low,structure maturity reaches medium,sorting is better,rounded is majorof sub-angular.The sandstone clastic particles are mainly point-line contact,cementation type ismajor of pore cementation.Reservoirs mostly develop residual intergranular pore, corrosionintergranular pore,intragranular dissolved pore.The average porosity of Chang2is12.57%,theaverage permeability of Chang2is0.74×10-3μm2;the average porosity of Chang3is8.96%,theaverage permeability of Chang3is0.24×10-3μm2;the average porosity of Chang4+5is7.48%,the average permeability of Chang4+5is0.32×10-3μm2.From the reservoirclassification of Chang2—Chang4+5we can see,the Ⅰ reservoirs developed less in the studyarea and only developed in some individual regions of Cahng2reservoir, the Ⅱ and Ⅲreservoirs distribute most in the area;Chang2reservoir is the advantageous reservoir in thestudy area.