Application Of Capillary Pressure Curve In Evaluation Of Tight Sandstone Reservoirs Logging Saturation

With the rapid development of the world economy today,the demand for oil and gas resources has shown a trend of continuous growth,thus placing higher demands on the petroleum industry.Most of China's conventional oil and gas fields have entered the late stage of development,making the petroleum industry attach great importance to the exploration and development of unconventional oil and gas reservoirs.As a kind of unconventional oil and gas reservoirs,tight sandstone oil and gas reservoirs are distributed in many areas of China and have great potential for production and development.In recent years,they have become the key targets for petroleum companies in oil and gas exploration and development.The study area is the KeShen area of the Tarim Basin,and the target layer is a tight sandstone reservoir.The reservoir has porosity,low permeability,poor physical properties,strong micro-heterogeneity and structural compression stress^[1],making the use of logging data to obtain the water saturation of tight sandstone gas reservoirs into a field study.The problem of work,and the lack of data on the saturation analysis,so the study of credible water saturation calculation method is of great significance to improve the credibility of fluid property evaluation.For tight sandstone reservoirs,in order to accurately identify the fluid type,in addition to obtaining accurate water saturation parameters,it is necessary to accurately evaluate the bound water saturation parameters.Accurately obtaining these two parameters is beneficial to improve the accuracy of fluid identification.Due to the difficulty in obtaining the water saturation of tight sandstone formations in the logging data of the study area,this paper analyzes the experimental data of core mercury in the study area,ignoring the influence of the core radius variation of the core and the ground,and establishes the laboratory capillary pressure and reservoir height.Transform the relationship.The J function method is used to eliminate the influence of lithology and physical properties,and the average capillary pressure and water saturation curve are classified according to porosity.The reservoir height and water saturation map are obtained,and the water saturation based on the capillary pressure curve of mercury intrusion is established.The calculation model of the degree also considers the influence of stress on the calculation of the formation water saturation of different stress segments,and verifies the mutual interpretation of the resistivity log,improves the accuracy of logging interpretation,and applies it to the study of reservoir fluid characteristics in the study area.In addition,based on the capillary pressure curve of the mercury in the study area,the lower limit of the pore throat of the study area was established by using the average inflection point of the mercury intrusion radius and the cumulative permeability value method.The capillary pressure curve was used according to the lower limit of the pore throat.Interpolation yields bound water saturation.The factors affecting the irreducible water saturation are analyzed.The results show that the irreducible water saturation has a good correlation with the median pore throat radius,and the median pore throat radius has a good correlation with the porosity to establish the bound water.The saturation interpretation model,and considering the stress-affected stress-segment segment to establish the interpretation model of the irreducible water saturation in the study area;due to the high cost of coring,it is impossible to take the core data of all the well sections in the whole study area.Therefore,in the absence of core experimental data,The bound water saturation can be further evaluated using the porosity of the log data.The established method of evaluating the irreducible water saturation and the water saturation evaluation method were applied to the logging interpretation of the research area,and good results were obtained.