Study On The Effectiveness Evaluation Method Of Tight Sandstone Reservoir In Western Kelasu Gas Reservoir

Tight sandstone gas is one of the four unconventional natural gases.Currently,the exploration and development of unconventional natural gas is mainly concentrated in tight sandstone gas.The annual production of tight sandstone gas in China accounts for an increasing proportion of total natural gas production.The characteristics of tight sandstone such as reservoir lithology,extremely low porosity permeability,complex pore structure,poor connectivity and strong heterogeneity,it brings great difficulties and challenges to exploration and development and construction of tight sandstone gas.Reservoir evaluation is classification and interpretation for reservoir with the actual situation of geology.With the deeply research of oil and gas exploration and development,the more attention is paid to the evaluation of tight sandstone reservoir.But the current domestic does not have a good solution to the study on effectiveness evaluation method for the tight sandstone reservoir.The Bashijiqike Formation of Cretaceous in western Crassus is a typical tight sandstone gas reservoir.In order to make a more accurate,reasonable and geologically-accurate reservoir classifications,this paper is obtained a set of evaluation method for tight sandstone reservoir in the research area with collection the data of core analysis,geological data,logging data and test data.It mainly includes the following steps:(1)It has certain understanding of the lithologic characteristics and physical properties of the reservoir in the study area through thin section analysis,physical property analysis,etc.;(2)Based on the analysis of the response of lithology to electric logging,the conventional well logging curve with high sensitivity to lithology is preferred.Density clustering nearest neighbor method and support vector machine method are used to form reservoir lithology identification methods suitable for the study area;Core calibration are used to convert elemental content into minerals.The conversion coefficient of the content is calibrated to improve the accuracy of ECS reservoir lithology identification.(3)Comprehensively consider the controlling effect of lithology,grain size,pore structure and other factors on the reservoir,use logging data and core analysis data to establish an accurate physical property parameter calculation model.Form the lower limit of the effectiveness evaluation parameters of tight sandstone reservoirs with combining the test gas data,empirical statistics method,data point constraint method,and minimum flow pore radius method.(4)The reservoirs are divided into four categories according to the Gas Well Capacity Division.Establish a comprehensive evaluation index for reservoir validity by comprehensive utilization of various macro and micro parameters,combination with nuclear magnetic T2 spectrum,Storage cover combination and Multivariate membership function.The actual well data was processed,and the evaluation indexes established were tested in combination with logging data,interpretation results,and gas test data.The verification results showed that the classification evaluation index of the tight sandstone reservoir established in this paper was in accordance with the actual production,and the accuracy was high.