Research On Numerical Testing Of Coalbed Methane Reservoir

In this paper, based on a large number of literature research, the adsorption, migration and output mechanism of methane are systematically and deeply analized and researched. Based on previous research, the mathematical models and numerical models of single-phase radial flow and two-phase of gas and water radial flow in fractal coalbed methane reservior are built and solved, and programs are developed. The main achievements are as follows:(1) The characteristic of fractal medium and the characteristics of quasi steady state and non-equilibrium adsorption of methane are considered, and the single-phase radial flow models in infinite fractal methane reservoir is built considering wellbore storage and skin effect. The model is solved by Laplace-transform and Stephest numerical inversion. A program is developed to plot the curves of dimensionless bottom pressure over time and the sensitivity of the dimensionless bottom pressure to the various parameters is analyzed and discussed.(2) The two-phase radial flow model of fractal coalbed methane reservoir are built considering the reservoir capabilities, migration and production mechanisms of coalbed methane. And the model is solved by IMPES methods. A program is developed to plot the curves of gas production over time when the inner boundary condition is constant bottomhole pressure and bottom pressure over time when the inner boundary condition is constant gas production. The sensitivity analysis of parameters is carried out with the two models.By comparing and analyzing the curves, the mathematical models of coalbed methane built in this paper are proved to be reasonable and reliable. They can describe the time-space process of the coalbed methane's migration well, and can reflect the characteristics of dual porosity media of the coal seams.