Production Evaluation of Well in Rectangular Coalbed Methane Reservoirs with Finite Conductivity Fracture and Matrix Shrinkage Effect

To make up the inadequacy of CBM reservoir productivity evaluation model, capacity evaluation model is proposed for matrix shrinkage properties. The paper expounds the influence of matrix shrinkage effect on the evaluation of CBM reservoir capacity. Combine with the steady state diffusion law, Darcy seepage law, Duhamel convolution and fracture diverting capacity conversion factor, introducing the new time function, it is realized that matrix shrinkage effect, finite conductivity crack and rectangular boundary are considered in CBM reservoir productivity evaluation. This paper studies the method to calculate the productivity evaluation model accurately and efficiently. Through the optimization and verification of the algorithm, it shows that the evaluation method has reached the strength of commercial software. The fitting results show that the new evaluation model can better fit the field production data, and the evaluation results are in line with the basic understanding of reservoir and gas reservoir, with small error.