Transient Pressure Analysis of Horizontal Wells in Anisotropic Naturally Fractured Reservoirs

Abstract

Summary Analytical solutions are presented for pressure-drawdown and -buildup analyses of horizontal wells in anisotropic reser voirs with tectonic, regional, or contractional natural fractures. (The reservoirs might be limited by parallel sealed boundaries.) These solutions have led to the identification of various flow periods, including radial in a vertical plane, transitional as a result of flow from the matrix into the fractures, linear when the transient pressure reaches the upper and lower boundaries of the reservoir, pseudoradial toward the wellbore in a horizontal plane, and linear when the transient reaches the outer parallel boundaries. Recognition of these flow periods leads to the calculation of pi or p*; permeabilities in the x, y, and z directions; storativity ratio, ω; average distance be tween natural fractures; fracture porosity; and fracture aperture, skin, and pseudoskin caused by vertical and horizontal partial penetra tion. Calculations are illustrated with an example.