Study On Stress Sensitivity Of Tight Sandstone Gas Reservoirs

This paper takes Xinjiang K block sandstone reservoir as the object of study.Based on the experimental analysis and theoretical research,the microscopic pore structure of the reservoir in K area,the deformation law of the porous medium,and the stress sensitivity of K reservoir are studied,and then,effect of stress sensitivity on gas well productivity,which are of great significance to guide the production practice of tight sandstone gas reservoirs.First of all,the high pressure mercury injection experiment was conducted to study the micro pore structure of reservoir through the relationship between pore structure parameters and core permeability.The results show that: the correlation between the main pore radius and replacement pressure with permeability is the best,for this reason,the classification standard of microscopic pore structure of reservoir is determined.Secondly,the influence of the deformation of porous media on the physical properties of the reservoir is analyzed,and the stress sensitivity model is established;The mechanism of stress sensitivity in porous media is studied through the simulation of pore scale flow.The results show that: the structural deformation of porous media has a little influence on porosity and has a great influence on permeability;The greater the tortuosity of the porous medium,the greater the stress sensitivity is;The bound water is attached to the pore throat in the form of water film,which makes the percolation abilit y of reservoir become worse.Furthermore,the conventional overburden pressure permeability experime nts validate the stress sensitive model of porosity,and obtain the conclusions that the porosity of tight sandstone reservoir stress sensitivity is weaker;The effects of differe nt experimental methods and sensitivity evaluation methods on the evaluation of reservoir stress sensitivity were studied by ultrahigh pressure stress sensitivity test.The results show that: the existence of bound water increases the stress sensitivity of reservoir;The stress loading method of changing confining pressure increases the stress sensitivity of reservoir;The industry standard method evaluates the reservoir stress sensitivity.Finally,the productivity equation considering the stress sensitivity is established,and the dynamic inflow curve considering the stress sensitivity is analyzed and compared,which provides the basis for reasonable exploitation of tight sandstone gas reservoirs.