Analysis Of Causes Of Microscopic Heterogeneity In Sandy Conglomerate Reservoirs

The Kebai area is an important region for oil and gas productivity,Permian Lower Wuerhe formation is an important oil-bearing series,Lower Wuerhe formation reservoir is a complex fan-delta sedimentary with glutenite as its main reservoir.Due to the large difference in single well production capacity and complex causes,the reasons have not yet been ascertained.The physical properties of reservoirs in different wells are very different,and the control mechanism has not yet been clarified,These have important implications for the development of current reservoir evaluations.Therefore,the research on the microscopic heterogeneity characteristics of glutenite reservoirs and the cause analysis are urgently needed to be solved.This articles takes the sandstone conglomerate reservoir of Lower Wuerhe formation in Kebai area of Junggar Basin as the research object,and takes the multidisciplinary knowledge of petroleum geology,sedimentary petrology and reservoir geology as the theoretical guiding ideology,combining core,logging data,etc.On the basis of respecting previous research results and drawing on the experiences of neighboring regions,reservoir sedimentary facies,petrological characteristics,reservoir properties,and reservoir diagenesis were studied in order.The above four parts were used to study the micro-heterogeneous characteristics and genesis of glutenite reservoirs.Finally,in conjunction with the above analysis,the following results and understanding have been achieved.The microscopic heterogeneity in the study area is mainly reflected in three aspects:grain(structure,roundness,sorting),interstitials(heterogeneous,cemented),and pore throat(pore diameter,pore type,mercury intrusion parameter).There are differences in the well area,and the same well,with the depth changes,the above three aspects are also significantly different,to a certain extent,reflects the strong heterogeneity.The differences in pore-throat parameters(including physical properties,pore type,pore size,expulsion pressure,median pressure,maximum pore throat radius,median pore throat radius,mercury removal efficiency,etc.)and sedimentary type were compared.The reservoir characteristics of low-heterogeneous traction-bound glutenite represented by rivers are obviously superior to gravitational flow glutenite represented by detrital flow;however,for example,the porosity is the lowest in gravitational flow glutenite and overlying siltstone.The traction flow glutenite pebbly sandstone and sandstone have the highest porosity.The compaction effect of the study interval is relatively strong,but there are differences in the compaction effects of different rock types.Among them,the scouring effect of the traction flow glutenite represented by the underwater distributary channel is relatively weak,and the gravity flow represented by the debris flow is relatively weak.The conglomerate compaction effect is relatively strong.The cement in the interval is less developed,and the cementation is not the main factor that causes the difference in reservoir performance;the clay minerals in the interval are mainly I/S mixed-layer minerals,mainly concentrated in the relatively close source area,and the rest are in Illite and Kaolinite.The content of stone and chlorite is less;the content of cement is negatively correlated with the porosity between 0 and 5%,and positive correlation is found when the content is greater than 5%,and the content of delaminated glutenite cement is more than 5% more than that of gravitational flow glutenite.Gravity flow glutenite reservoirs mainly consist of secondary dissolved pores and microfractures,and the proportion of primary intergranular pores is relatively low.Traction glutenite mainly consists of primary intergranular pores,and the dissolution pores are mainly granular.Edge dissolution hole,the proportion of secondary dissolution holes is relatively low.The existence of micro-fractures can promote the development of dissolution.Gravity flow glutenite micro-cracks are more developed than traction flow gluten.