The Research Of Conductive Mechanism And Productivity Prediction Of Low Porosity And Low Permeability Reservoir In A Area

Low porosity and low permeability reservoir is one of the key research item in the current oil exploration and development field,and the exploration and development of this kind reservoir is the significant component in securing a steady oil supply and improving reserve for old oil field.Compared with the conventional oil and gas reservoir,low porosity and low permeability reservoir have the characteristics of poor physical property,complicated pore structure,strong heterogeneity,large electric difference in a set of reservoir,and so on,which resulting in more problems at reservoir logging interpretation evaluation.Now,determine the influence factors of reservoir electrical characteristic and the reservoir productivity prediction evaluation of different types of reservoir are the urgent issue in well logging research.Based on the actual reservoir characteristics,the study of conductive mechanism and productivity prediction of complex low porosity and low permeability is carried out by a combination of core experiment,theoretical analysis and numerical simulation technology,providing foundation for reservoir effectively exploration and development.Based on the basic reservoir characteristics and four reservoir correlation characteristics,digital core numerical simulation and mud reservoir simulation technology are applied to study conductive mechanism from the internal factors and external conditions,respectively.The actual gas cores are used to construct the 3D multicomponent digital core model,and analyze the influence of the gas reservoir rock electrical properties from the micro-level,including rock mineral composition,pore structure,formation water salinity.Though establishing a limited-size 3D single-well stratum model,acquireing the law of mud invasion and the influence of formation resistivity properties around the well.The results show that the reservoir electrical property is always the result of multiple factors.The formation resistivity decreases with the increase of the clay mineral content,conductive mineral content,good physical properties,good pore structure,formation water salinity.When the mud invasion occurs,the invasion capacity become strong in good physical properties and pore structure reservoir,and the resistivity decreased around the well,which lead to low electric logging response.The study reveals the conductive mechanism from the internal factors and external conditions of reservoir,gives the main controlling factor and the quantitative cause ordering of low resistivity reservoir.Based on quantitative relation study,the quantitative order of main factors are as follows: physical properties,clay content,heavy mineral content and formation water salinity.Based on the research of reservoir characteristics and conductive mechanism,parameter calculation model and resistivity correction are conducted in-depth research.Multiple porosity and permeability quantitative model are set up based on the differences of each layer.Based on the law of mud invasion,the resistivity correction method of time lapse and invasion inversion are established according to physical properties,invasion conditions and electric logging response based on mud invasion numerical simulation.The calculation accuracy of water saturation parameters can be improved by the corrected formation resistivity.Considering the additional conductivity of clay component,Simandoux equation is adopted to calculate the water saturation.Considering the conductivity of clay component,micro-porous water and free water,as well as the effect of conductive element form and structure,a water saturation model is proposed with symmetrical effective medium conductance theory.Actual application indicate that the calculation accuracy of effective media saturation model is more suitable to real formation,which can be used for quantitative evaluation the water saturation of target area.The paper analysis the sensitivity factors of reservoir productivity by numerical simulation technology.The results shows that the gas production rate increased linearly with the increase of the square of production pressure difference,effective thickness,prosity-permeability composite index,gas saturation,and these are the main influence factors of reservoir production capacity.The production parameters calculation equation are set up according to conventional log data and MDT test technology.Based on the analysis of the four relationships in the study area,the differences of different types of low permeability reservoir characteristics are analysised through the digital core explicit analysis.C ombine with the characteristics of fluid distribution and poroperm of the formation,four "property-electrical-capacity" divide the pattern are proposed,which can effective interpretation the relationship of reservoir characteristics and production capacity,improving the discriminant ability of logging in reservoir productivity.By using the reservoir parameters and logging information,weighting coefficient method,the planar radial flow based model and RBF neural network model are built in quantitative calculating reservoir production.Comparing the application of the models,the method based on planar radial flow which a lithology factor and a conductive factor are introduced to model has higher evaluation accuracy,which is suitable for the study area.The method based on RBF neural network has good prediction effect,this method can be used for productivity evaluation and prediction in the study area.