The Evaluation Of Conductance Mechanism And Saturation Logging Of Tight Sandstone In XX Block

Saturation logging evaluation is the core of quantitative evaluation of oil and gas reservoirs,the most commonly used method for calculating saturation is logging,it is based on the classical Archie model.The classical Archie model based on the middle and high porosity and permeability reservoir rock samples is not suitable for tight sandstone gas reservoirs,therefore,it is necessary to carry out the evaluation of conductance mechanism and saturation logging of tight sandstone gas reservoir.The study area locate in Jinxi flexual fold belt in East Erdos basin,the sedimentary environment of Shihezi Formation is braided river delta deposit,the channel sand body is the favorable exploration reservoir sand body.The reservoir rock composition is complex,the main lithology is lithic quartz sandstone and lithic sandstone;the physical condition is poor,it belongs to the typical tight reservoir;There are residual intergranular pores,intergranular pores,intragranular dissolved pores,intergranular pores and fracture pores,the pore types are various,the secondary pores are well developed,the pore structure is poor and its difference is obvious,the compaction,the cementation and the diagenesis are strong,which have a great influence on the size and type of the pore space.Resistivity logging is the basic data for evaluating oil and gas saturation,there are some low resistance gas reservoirs in tight sandstone of research area,studying on the main cause of low resistance gas reservoir,and according to the cause,making the low resistance correction.to make sure the accuracy of resistivity logging.According to the geological and rock characteristics of the study area,based on the experimental data of the rock samples,the main causes of low resistance gas reservoir are studied from the four aspects: the role of high water saturation,the additional conductivity of clay,the role of conductive minerals and the drilling fluid invasion,and the drilling fluid invasion is decided to be the main cause of low resistance gas resistance.Through numerical simulation,the effects of porosity,permeability,gas saturation and salinity on drilling fluid invasion are analyzed,finally,the resistivity correction chart is established,to a certain extent,improving the accuracy of logging prediction.The study of conductance mechanism is the foundation and key of establishing saturation model.The resistivity data of rock samples are analyzed and studied,it is found that the relationship between formation factor F and porosity ?,resistivity index I and water saturation Sw is non Archie;from the four aspects of reservoir physical properties,rock composition,pore type and pore structure,the main factors affecting the rock electrical parameters are confirmed to be the pore types,and it is controlled by diagenesis;considering the effects of compaction,cementation and dissolution on the formation of rock and pore space,according to the difference of pore type,there are differences in I-Sw relationship,and there are two kinds of trend: power and exponential,the relationship between F-? is also different according to the difference of pore type.According to the logging response characteristics of different pore types,the logging curves are optimized,Fisher discriminant analysis method is used to establish the logging discriminant criteria for different pore types;according to the conductance mechanism of the research area,logging prediction model of cementation index m and saturation index n is established for different pore types,finally,the improved variable rock electrical parameters Archie saturation model is established.The improved variable rock electrical parameters Archie saturation model is applied for saturation logging evaluation in study area,the logging prediction value and the rock samples value of saturation are contrasted,the improved variable rock electrical parameters Archie saturation model is better than the Archie saturation model and the Indonesia saturation model,the average relative error is 8.9%,which verifies the reliability of the saturation model,it can also be used as a reference for the saturation logging evaluation methods of similar research area.