Pressure Transient and Decline Curve Behaviors for Partially Penetrating Wells Completed in Naturally Fractured-Vuggy Reservoirs

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis work presents results on both pressure and production responses during transient and boundary-dominated flow periods, in naturally fractured reservoirs with vuggy porosity. It is considered that triple-porosity systems may not be treated as dual-porosity reservoirs, mainly because fractures and vugs have different geological origin and therefore their interaction with matrix blocks do not have to be similar. New solutions are presented for the case where there is no primary flow through vugs, an extension of the Warren and Root model, existing an interaction between matrix, vugs, and fracture systems.The new model assumes a single partially penetrating well producing from an undersaturated system considering several boundary conditions. The inner boundary condition at the wellbore can be considered either a fixed flux or constant pressure boundary. The upper, lower, and outer boundaries can be modeled at constant pressure or prescribed flux. These boundaries can be closed, or the influx can be modeled via a step rate or a ramp rate function. The step rate function could represent a waterflood effect and the ramp rate function a natural waterdrive or gas drive cap effect. The transient pressure response is also analyzed by considering an infinite outer boundary. In transient well tests and decline curve analysis, the effects of triple-porosity for different upper and lower boundaries conditions are analyzed, besides considering closed upper and lower boundaries as it has been done in the literature. It is shown that for triple porosity systems the derivative function may exhibit different behavior to that of double-porosity reservoirs. It is demonstrated that the presence of vugs and caves may have a definitive influence on transient well test and decline curve behaviors. Synthetic and field examples are presented to illustrate the methodology proposed in this work.

Partially Penetrated Well Solution of Fractal Single-Porosity Naturally Fractured Reservoirs

“…In the literature, several analytical solutions for modeling the behavior of pressure-transient tests of partially penetrated wells have been proposed [1][2][3][4][5][6][7][8][9][10]. Some of these works have proposed the use of point and line source solutions derived in the Laplace space, considering finite and infinite systems, with homogeneous and naturally fractured reservoirs [2,5,6,8,10]. Other studies considered gas anisotropic reservoirs using a uniform flow solution [9].…”

An Analytical Solution of Partially Penetrating Hydraulic Fractures in a Box-Shaped Reservoir

“…In the late time, Ozkan and Raghavan [8] proposed a solution for a limited-entry slanted well in an infinite reservoir with closed top and bottom boundaries using the Laplace transformation and Bui et al [9] used the double-porosity formulation of Warren and Root for naturally fractured reservoir. Fuentes-Cruz and Camacho-Velazquez [10] obtained the pressure transient behavior for partially penetrating wells completed in naturally fracturedvuggy reservoir by combination of Laplace transformation and finite Fourier transformation.…”

Pressure Transient Analysis for Finite Conductivity Multi-staged Fractured Horizontal Well in Fractured-Vuggy Carbonate Reservoirs

“…G. Fuentes-Cruz et al [4] studied the transient pressure and production decline curve behaviors for partially penetrating wells completed in fractured-vuggy reservoirs. Camacho-Velázquez et al [5] proposed an unsteady flow analysis model for carbonate reservoirs, and analyzed the transient pressure and production decline curves.…”