Well Log Reservoir Evaluation And Research Of Sinian System Dengying Formation Of Gm Area In The Middle Of Sichuan Basin

GM area in the middle of Sichuan basin is a new exploration area,the previous studies degree of which is relatively low,and old strata,thick formation,developed dissolution,strong reservoir heterogeneity are its obvious characteristics.The quantitative calculation of reservoir parameters is difficult,the study of the fluid distribution characteristics is not deep,so the fine interpretation of reservoir parameters,accurate fluid identification standard,reservoir classification and comprehensive evaluation are urgent need to do,which has important influence on the future geological modeling and development plan.So many works were done in this paper,such as,interpreted the lithology of Dengying formation and reservoir parameters,analyzed the four features of reservoir,interpreted the imaging logging,identified reservoir fluid,researched on the reservoir characteristics and finally evaluated the reservoir types by using the core data,geological data,testing data,log data and so on.On the basis of above research results,summarized the development characteristics of reservoir of the Dengying Formation in GM area.By the use of core data and thin section which come from 5 coring wells,the main lithology in study area are straticulate dolostone,algal clot dolomite,micritic dolomite,second development is argillaceous dolomite,siliceous rock is at least.According to the principle of nonlinear neural network,set up the lithologic identification neural network model in study area,and explained the lithology of single well.Observed the core photos and the casting thin sections,reservoir space of study area is main pore,cave,and cracks is second.Based on studying the core physical properties data of 5 core wells,the matrix porosity of Z₂dn⁴ is mainly distributed in2%⁴%,the whole diameter sample porosity is mainly concentrated in 2%⁸%;the matrix porosity and the whole diameter sample porosity of Z₂dn² is mainly distributed in 2%⁴%,but the whole diameter sample porosity is better than that of the plunger sample.The permeability of Z₂dn⁴ range from 0.001×10^-3?m² to 1×10^-3?m²,the permeability of Z₂dn₂ mainly distributed between 0.01×10^-3?m² and 1×10^-3?m².On the whole,the physical properties of Z₂dn⁴ is better than Z₂dn².In addition,researched the microscopic pore structure characteristics by experimental data of capillary pressure of 3 wells in the study area,the characteristics of pore structure are divided into 3 types.Reservoir of study area is mainly of big-medium hole,medium-fine throat microscopic pore structure,the pore throat sorting is poor,and heterogeneity is strong.Through anlysising the K-?crossplot,found that the study area reservoir in hole-crack double medium.The reservoir types are given priority to pore-holes and cave reservoir,cracks-hole is less.Chose the best modle thhrough a variety of methods contrasting.The research and comparison show that clay content used the t empirical formula;by"core calibration logging"and the principle of nonlinear neural network,porosity models are built up in each layer;according to the types of reservoir space,different reservoir space in Z₂dn⁴and Z₂dn² is established different neural network permeability model.The reservoir in the study area is of low clay content,so select the Archie formula to calculate water saturation.Through the core and imaging logging data,the imaging logging model in the study area is divided into five categories and 16 small classes,imaging logging interpretation model library is established in the study area.The fluid of study area is natural gas and water.By using test data,core data and logging data,using the porosity and?^Sw cross plot and Rt^Rxo cross plot method to identify gas and water.the coincidence rate of the plate is over 80%.Based on the identify fluid results of single well,to study the characteristics of fluid distribution,From the vertical up of Z₂dn⁴main develop gas,the thickness of gas reservoir in upper of Z₂dn⁴ is more obvious thicker than the lower of Z₂dn⁴.Z₂dn² is visible gas layer and water layer,the thickness of the water layer is relatively large.From the point of view of single well distribution,the gas in west developed better than the east.On the basis of the interpretation of reservoir parameters and gas water identification in study area,To determine the lower limit of porosity by minimum flowing pore throat radius method,Through the relationship between the pore with saturation method which determined by mercury injection data,and analogy method to research the gas standard.Through this study,to determine the longitudinal use a petrophysical lower,the porosity limit is 2%and the gas saturation limit is 50%.Based on dividing the effective thickness,porosity,permeability,selection of gas saturation,pore throat types are used as the reservoir evaluation parameters,through reservoir classification research to the reservoir in the study area,the reservoir is divided into three categories,and develop the reservoir classification standard.Based on the standard of reservior classification and evaluation,the comprehensive reservoir classification and evaluation all of single well in the study area were done.In the view of the single well reservoir evaluation,analysed the vertical and horizontal distribution characteristicks of reservoir.Study area can be main obtained for class III reservoir,class II reservoir is second,class I reservoir develop rarely.On vertical,the reservior in the upper of Z₂dn⁴ and Z₂dn² develop.