Inversion Method And Application Of Fracture Network Parameters In Deep Shale Gas Reservoirs Based On Dynamic Analysis Method

Deep shale gas is an important field of natural gas production in China in the future.Compared with shallow shale gas,on the one hand,the deep shale gas has high stress and it is difficult to add sand during fracturing.And it is difficult for proppants to enter the far end of the fracture,the fracture stress sensitivity is stronger,and the influence of nonlinear seepage is greater.On the other hand,the flowback rate of fracturing fluid is low,a large amount of fracturing fluid is remained in the reservoir,and the characteristics of gas-water two-phase seepage are obvious.Existing fracture network parameter inversion methods ignore the influence of incompletely propped fractures and gas-water two-phase seepage in fractures on the development of deep shale gas reservoirs.To solve this problem,based on the zoning idea and according to the fracturing characteristics of deep shale,the physical model of SRV is extracted to establish a gaswater two-phase seepage model considering multiple nonlinear seepage mechanisms,incompletely propped fractures and variable fracture conductivity.Secondly,the nonlinear factors in the seepage model are processed by means of variable substitution,perturbation transformation,and successive substitution,and a gas-water two-phase productivity prediction method considering incompletely propped fractures is established and solved analytically.Then,the influence of fracture and reservoir parameters on the gas production and water production is analyzed by single factor analysis method,and the initial production and cumulative production are taken as the evaluation indicators.The key parameters of inversion are extracted,and the half-length of fracture,the halflength and permeability of propped fracture are interpreted by water production,and permeability of inner SRV,outer SRV and unpropped fracture are interpreted by gas production.Finally,a parameter inversion method for deep shale gas fracture network is established based on dynamic analysis method,and its application is analyzed for four deep shale gas wells in Sichuan Basin.The results show that when considering incompletely propped fractures and gas-water two-phase seepage,the model fits better,and the interpreted parameters are more reliable.The parameter inversion method established considers the influence of gas-water coproduction on productivity prediction and parameter inversion,and can quantitatively distinguish between propped and unpropped fractures with parameters such as half-length and permeability,providing theoretical guidance for accurate calculation of deep shale gas production and evaluation of fracturing effect.