Analytical Model for Rate Transient Behavior of Co-Production between Coalbed Methane and Tight Gas Reservoirs

Due to complex geological structures and potential environmental impacts, single-well production in coal-measure gas reservoirs is not satisfactory. Field studies have shown that co-production is a promising approach, which can efficiently and economically extract multiple gas resources. However, the literature lacks a mathematical model to accurately describe and predict the production behavior during co-production. Based on the five-linear flow model, this work presents an analytical solution to evaluate the production dynamics characteristics of co-production between coalbed methane and tight gas reservoirs. In addition, the proposed model accounts for factors such as dual-porosity media, the gas slippage effect, and the matrix shrinkage effect. With the aid of the model, sensitivity analyses of the Blasingame decline curve and the layered flux contribution are conducted. The calculation results show that a higher fracture conductivity, as well as a longer fracture length, lead to larger cumulative production. Additionally, increased layer thickness significantly boosts flux contribution throughout the production period. Finally, large boundary distances extend the duration of high flux contributions in late production. This research contributes to a better understanding of the production dynamics in coal-measure gas reservoirs and offers practical guidelines for reservoir management in co-production scenarios.