The Study On The Effects Of Temperature And Pressure On Gas Flow And Mass Transfer In Fractured Tight Reservoirs

The deep naturally fractured tight reservoir is of great resources,whereas,the reservoir is characterized with low porosity and low pressure,hardly forming an effective system of seepage.There are large number of natural fractures in tight reservoir,which is the key factor to improve the seepage characteristics of tight reservoirs.After hydraulic fracturing,natural fractures are activated,and connect with hydraulic fractures to form complex fracture networks,the pressure loss of gas flowing through each media is different which have a significant impact on gas flow in matrix-fracture system under the condition of high temperature and high pressure.The main methods to study the law of gas flow in stimulated reservoirs are numerical simulation and physical experiment.Numerical simulation method takes the effects of temperature,stress and other factors into account to some extent,and most of the numerical models simplify the gas flow which cannot accurately characterize the gas slippage in the matrix and non-Darcy flow in fractures under different temperature and pressure conditions in deep tight gas reservoirs.Due to the constraint of experimental methodology,most of the experiments are conducted under the room temperature and relatively low pressure,while the physical simulation technology under the high pressure and high temperature has not been well developed,impeding the understanding of the gas flow mechanism in the deep reservoir and the development and advancement of gas flow models.In this study,the Keshen naturally fractured tight gas reservoir in the Tarim Basin is targeted as our research area.Our study was mainly conducted through physical simulation.The pressure and temperature condition and the matrix-fracture connecting way were improved to physically simulate the processes of gas flow from matrix to natural and hydraulic fractures as well as matrix-fracture mass transfer under the high pressure and high temperature conditions.The gas flow under different thermal and stress conditions were compared and analyzed,and the combined influences of fracture connectivity,stress and flow regime on gas flow mechanism under conditions of high pressure and temperature will be identified.The results show that the influence of gas pressure on gas flow and node pressure is more obvious than temperature.The increase of effective stress and the increase of temperature leads to decrease of gas permeability of various cores,weakening of gas slippage effect,and increase of stress sensitivity.The gas flow in the core with fracture running through both end faces is more sensitive to temperature and pressure.Our study could thoroughly improve the understanding of gas flow mechanism after hydraulic fracturing,and provide experimental and theoretical foundation for the effective development of tight gas in deep reservoir.