Study On Logging Comprehensive Evaluation Method Of Tight Sandstone Reservoir

The tight sandstone reservoirs of Shanxi-Taiyuan Formation in Hangjinqi J58 and J72 well areas in the northern Ordos Basin are characterized by varied rocks and minerals,complex lithology,fracture development,poor physical property and strong heterogeneity.Therefore,it is difficult to calculate the reservoir parameters,which brings some challenges to the research on the comprehensive evaluation method of tight reservoirs.This paper summarizes the predecessors' research,based on the theory of group-taiyuan in Shanxi Province in northern ordos basin adapted area reservoir as the research object,using the combination of subject knowledge on geology,well logging,from the work area of the reservoir rock mineral,lithology,physical properties and pore structure characteristics analysis,and combined with the analysis of logging data and test data,From both macroscopic and microscopic aspects,the reservoir characteristics,calculation methods of key reservoir parameters,pore structure and water content of the target reservoir in the study area were systematically studied.Finally,a comprehensive evaluation method model suitable for the tight sandstone reservoir in the study area was established.Aiming at the problems existing in the study area,the research work is focused on five aspects:lithology,lithofacies identification and characterization,key parameter calculation method,pore structure analysis and water cut calculation model construction of the target tight sandstone reservoir.Firstly,in view of the complex lithology changes in tight reservoirs,core lithology calibration logging is used to find out the lithology sensitive data,establish the lithology identification chart of complex lithology response,and then establish the lithology identification model,and form the lithology spectrum method for quantitative and intuitive identification and characterization of lithology.Secondly,based on the particle size analysis and the sedimentary tectonic background of the study area,the lithofacies types of the target intervals in the study area were classified,and the intelligent identification and classification method of lithofacies was established by using the T-SNE dimension reduction function.At the same time,the relationship between pore and permeability of tight reservoir core analysis and logging response is analyzed.By selecting sensitive curves,a multivariate fitting inversion method model for physical property parameters(porosity and permeability)of tight sandstone reservoir is established.The accuracy of the method is verified by comparing the core analysis data with the results calculated by the model.Then,this paper evaluates the pore structure of the tight sandstone reservoir from two aspects:qualitative description(casting thin section observation)and quantitative characterization(mercury injection method).Secondly,aiming at the water effluent problem in the actual production of the target interval in the study area,the water content calculation model of the target interval is established.The key to the calculation of water content is to accurately obtain the relative permeability of gas and water phases.In this paper,two methods are used to solve the relative permeability of gas and water phases.One is the conventional method,which establishes a model to predict the ratio of relative permeability of gas and water phases based on the pore structure index by analyzing the experimental results of phase permeability.The other is the neural network method,which is based on RBF neural network to predict the relative permeability model of gas and water phase.The results of the two models are compared with the actual production data to verify the effectiveness of the models.Finally,by studying the relationships and rules among the various properties(rock minerals,lithology,lithofacies,physical properties,pore structure and water content)of the tight reservoir,a comprehensive characterization and evaluation method model suitable for the target interval of the tight sandstone reservoir in the study area was established.