Waterflood technique with pressure fluctuation, especially with low, ultra low frequency, changes the continuous water flow into the flow with pressure fluctuation, and can prevent contamination precipitation, formati...Waterflood technique with pressure fluctuation, especially with low, ultra low frequency, changes the continuous water flow into the flow with pressure fluctuation, and can prevent contamination precipitation, formation plugging and Jamin effect. It also can prevent the plugging of water injection well, decrease the pressure of waterflood and increase the rate of water injection. On the basis of the existing eccentric injection mandrel, used the energy storage character of air energy accumulator and the pressure switch character of pressure control valve, fixed the plunger valve for pressure control on the position of blanking plug, then developed one new injection mandrel with low frequency character, which can inject water continuously with low, ultra low frequency. Water fluctuation produced during the water injection affect the formation directly and is useful to break down, prevent plugging and augment injection.展开更多
Based on fractal geometry,fractal medium of coalbed methane mathematical model is established by Langmuir isotherm adsorption formula,Fick's diffusion law,Laplace transform formula,considering the well bore storag...Based on fractal geometry,fractal medium of coalbed methane mathematical model is established by Langmuir isotherm adsorption formula,Fick's diffusion law,Laplace transform formula,considering the well bore storage effect and skin effect.The Laplace transform finite difference method is used to solve the mathematical model.With Stehfest numerical inversion,the distribution of dimensionless well bore flowing pressure and its derivative was obtained in real space.According to compare with the results from the analytical method,the result from Laplace transform finite difference method turns out to be accurate.The influence factors are analyzed,including fractal dimension,fractal index,skin factor,well bore storage coefficient,energy storage ratio,interporosity flow coefficient and the adsorption factor.The calculating error of Laplace transform difference method is small.Laplace transform difference method has advantages in well-test application since any moment simulation does not rely on other moment results and space grid.展开更多
文摘Waterflood technique with pressure fluctuation, especially with low, ultra low frequency, changes the continuous water flow into the flow with pressure fluctuation, and can prevent contamination precipitation, formation plugging and Jamin effect. It also can prevent the plugging of water injection well, decrease the pressure of waterflood and increase the rate of water injection. On the basis of the existing eccentric injection mandrel, used the energy storage character of air energy accumulator and the pressure switch character of pressure control valve, fixed the plunger valve for pressure control on the position of blanking plug, then developed one new injection mandrel with low frequency character, which can inject water continuously with low, ultra low frequency. Water fluctuation produced during the water injection affect the formation directly and is useful to break down, prevent plugging and augment injection.
基金This researchwas supported by the Scientific Research Project of the Heilongjiang Education Department(Grant No:12521044).
文摘Based on fractal geometry,fractal medium of coalbed methane mathematical model is established by Langmuir isotherm adsorption formula,Fick's diffusion law,Laplace transform formula,considering the well bore storage effect and skin effect.The Laplace transform finite difference method is used to solve the mathematical model.With Stehfest numerical inversion,the distribution of dimensionless well bore flowing pressure and its derivative was obtained in real space.According to compare with the results from the analytical method,the result from Laplace transform finite difference method turns out to be accurate.The influence factors are analyzed,including fractal dimension,fractal index,skin factor,well bore storage coefficient,energy storage ratio,interporosity flow coefficient and the adsorption factor.The calculating error of Laplace transform difference method is small.Laplace transform difference method has advantages in well-test application since any moment simulation does not rely on other moment results and space grid.
