Decline Curve Analysis with Type Curves for Variable Rate/Variable Pressure Drop in Stress Sensitive Naturally Fractured Shale Gas Reservoirs

Blasingame production decline analysis can be applied to variable production/pressure drop systems, so this method has a wider applicability. Due to the multiple flow mechanisms and stress sensitivity of gas reservoirs in shale, there is limited research on Blasingame decline analysis focused on these two key points simultaneously. In this paper, a semi analytical Blasingame decline analysis model is proposed, which takes into account the adsorption and desorption to improve material balance pseudo-time. The perturbation method is used to solve the mathematical problems caused by stress sensitivity, and further combined with the Laplace transform, point source function, numerical discrete method and Gaussian elimination method, the problem of non convergence of the control equation caused by multiple flow mechanisms is solved. Based on the Blasingame production decline analysis model, the production data of domestic WY shale block development wells were analyzed, including inversion of reservoir parameters and prediction of production well production decline patterns. According to the application of this new method on WY shale block, it found that the overall fitting effect is good, except for the poor fitting between the early production data of the gas well and the theoretical chart, which is related to the early backflow of water from the production well and the consideration of single-phase gas flow in this model. Furthermore, the sensitivity of permeability stress to porosity and diffusion coefficient stress is a trade-off.