Study On The Morphology Of Tight Gas Reservoir Gas-water Relative Permeability Curve And The Characterization Of Permeability Jail

Tight-gas reservoirs are characterized by low permeability,low production and low pressure.In addition,most of the reservoirs are micro-nano pores,and the heterogeneity of the reservoirs is strong.Therefore,the development technology of tight gas reservoirs is difficult and the investment cost is high.In addition,the complex pore structure makes the gas-water permeability curve of tight gas reservoir various,and the accurate description of the permeability curve is the basic guarantee of gas reservoir dynamic analysis.Therefore,the study of gas-water permeability curve characterization and fine characterization can provide scientific support for the efficient development of tight gas reservoirs.In this thesis,laboratory experiments and n?merical simulations were used as technical means,and the micro-pore structure characteristics,gas-water relative permeability curve morphology and the corresponding relationship between the two were determined by the experimental results of low-temperature liquid nitrogen adsorption,high-pressure mercury injection,nuclear magnetic resonance,centrifugation,and gas-water permeability.Combined with n?merical simulation and economic evaluation,the influence of different types of gas-water relative permeability curves on production was revealed.On this basis,the generalized permeability jail was further characterized,and the corresponding pore structure parameter range was studied.The main achievements and understandings of this paper are as follows:(1)The microscopic pore structure characteristics of tight gas reservoir were obtained.The pore types are impermeable pores,open type wedge V-shaped pores and fracture pores,and the specific surface area of pore throat ranges from 0.05-4.06 m~2/g.The BJH pore vol?me ranges from0.0014 to 0.0207 m L/g,and the average pore throat radius ranges from 0.179 to 1.031?m.(2)The morphology of gas-water permeability curve of tight gas reservoir is defined,and the relationship between the microscopic pore structure and the morphology of gas-water relative permeability curve is established.According to the characteristic points,the gas-water relative permeability curves can be divided into 6 types.The first type of reservoir properties and seepage capacity are the best,the second and third types of curves are slightly better,the fourth and fifth types of curves are the next,and the sixth types of curves are the worst.(3)Different types of curves will lead to the change of recovery efficiency,which will lead to the decrease of profit rate.Recovery efficiency and profit rate gradually deteriorate from type I to type VI,among which type IV,type V and type VI curves have a generalized permeability jail.(4)The general permeability jail of tight sandstone permeability curve is that the relative permeability of gas and water is less than 0.06;According to the microscopic pore structure characterization,the phenomenon of generalized permeability jail zone exists in the gas-water relative permeability curve of rock samples with fracture pore type,specific surface greater than1.96 m~2/g,average pore throat radius less than 0.2?m,characteristic structural parameters less than 3.815,and displacement pressure greater than 0.875 MPa.