Analysis of horizontal well pressure behaviour in fractured low permeability reservoirs with consideration of the threshold pressure gradient

This paper presents a mathematical model for the analysis of the transient pressure behaviour of a horizontal well in naturally fractured low permeability reservoirs, which takes the threshold pressure gradient (TPG) into consideration. Then, the solution of this model is obtained by using the method of Laplace transform and Fourier cosine transform, and the type curves are plotted by the Stehfest numerical inversion method. Pressure behaviour is analysed by examining the pressure drawdown curves, the derivative plots and the effect of the characteristic parameters. The typical pressure response of this reservoir is presented by the following five flow regimes: (1) wellbore storage and transition flow; (2) early radial flow in the vertical plane; (3) line flow in the horizontal plane; (4) matrix-fracture system transition flow; and (5) later pseudo-radial flow affected by the TPG. At the end, a field application manifests the correctness of the solutions derived in this paper, and the results have both theoretical and practical significance in predicting the production behaviour of carbonate reservoirs and evaluating fluid flow and transport in such a formation. (paper)