Research On Water Intrusion Evaluation Method Of Tight Sandstone Based On Equivalent Capillary Network

Tight sandstone gas reservoir is the future of natural gas,as the most important part of low permeability reservoir,which has the ability to compensate the reserves and production decline of conventional oil and gas reservoir.Tight sandstone gas reservoir is gradually becoming the focus of exploration and development at home and abroad.However,due to the tight sandstone reservoir pore network space is extremely complex and small,in the process of drilling and completion,the working fluid is easily invading into the deep reservoir under the action of capillary force,which will cause irreversible formation damage.Therefore,the research of formation damage evaluation method has the extensive applicability and pracitcal instrction significance to the further objective and true evaluation of formation damage,which reveals the essence of aqueous phase invading porous media from the microscopic scale,and calculates the radius of fluid invasion.Take Sichuan HC area Xujiahe formation as resarch project.The paper focuses on the typical pore structure in tight sandstone reservoir by comprehensive utilization of theoretical research,laboratory experiment and mathematical model method,and detailed reveals the mechanism of aqueous phase invading porous media in tight sandstone formation.The main works of thesis are as follows:(1)With the help of casting thin slice,scanning electron microscope,conventional mercury penetration experiment and rate-controlled mercury penetration experiment,the paper describes the characteristics of micro pore structure in the tight sandstone reservoir qualitatively and quantitatively,provides petrophysical parameters for the subsequent model research.(2)Based on the characteristics of tight sandstone porous media,a series of aqueous phase invading pore network visual experiments were conducted by using laser etched microscopic pore network model.By comprehensive utilization of theoretical research,laboratory experiment to quantitatively reveal the features of fluid invasion in pore network model,which provided a basis for the mathematical model study.(3)Capillary bundle model for tight sandstone pore network was established by the data from conventional mercury penetration experiment.Tortuosity which was used to update the physical model could ensure that porosity and permeability in physical model was consistent with real rock.(4)Based on the capillary kinetic theory and capillary bundle model,mathematical model for water invading pore medium was established.The damage of water invading pore medium was evaluated based on mathematical model.(5)Finally,the effectiveness of mathematical model was discussed based on experiment of aqueous phase invading porous media and core imbibition.The new evaluation method of aqueous phase invading tight sandstone reservoirs was validated to be effective.