Pressure Transient Analysis For Coalbed Wells

On the basis of the extended studies of well test analysis of the coalbed methane and double porosity the physical models, this thesis makes a analysis of the character that fluid flow through double porosity media of underground, and it is applied for the mathematical models of pressure transient analysis for coalbed wells. According to unsteady state diffusion and pseudo-steady state diffusion, it is carried out that Laplace's solutions through the establishment and computation of mathematical model. In addition, there is a initial condition, two inner boundary conditions and three different outer boundary conditions in order to make a accurate solution in the mathematical models. And it is defined that wellbore storage effect, skin factor and effective wellbore radius in order to obtain the different explain. Through the exact inversions method of the presented solutions form Laplacian space, we can obtain the dimensionless pressure, and derivate curves.In the modern well test analysis, the coalbed methane well test transient analysis in this thesis is looks as double porosity media. Through the combination between the diffusion in the matrix and the flow in the fissure, the equation of continuity including the diffusion phase is obtained. Dimensionless forms can simplify mathematical models. The characteristic equation is developed to directly calculate the parameters of fluid capacitance coefficients and interporosity flow coefficients.At last the gas reservoir is analyzed through actual data of it. And some parameters can be obtained by fitting with theory chart.