Pressure Transient and Decline Curve Behaviors in Naturally Fractured Vuggy Carbonate Reservoirs

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis study presents a new way to model high secondary porosity, mainly vuggy porosity, in naturally fractured reservoirs.New solutions are presented for two cases, where there is no primary flow through the vugs, which is an extension of the Warren and Root model, and where dissolution process of pore throats has created an interconnected system of vugs and caves. In both cases there is an interaction between matrix, vugs, and fracture systems. New insights are provided.Both pressure and production responses during transient and boundary dominated flow periods are explored. In transient well tests, for the case where there is no primary flow through the vugs, a change of slope could be present during the transition period. Thus, this study shows that slope ratios of 2:1 of early or late-time segment versus transition segment do not necessarily imply transient interaction between matrix and fractures. It is also shown that the presence of vugs and caves may have a definitive influence on decline curve and cumulative production behaviors; therefore it is necessary to incorporate vuggy porosity in the process of type curve match.Finally, the use of the methodology obtained in this work is illustrated with synthetic and field examples.

Application of Fractional Calculus to Oil Industry

“…[1,2]), usually it is possible to discern three porosity types: matrix, fracture, and vugs; with this conception, it is accepted that the three porosities have associated a solid phase, and with this both Continuity Equation and Darcy's law can be expressed for each fluid in each geometrical media. If we only consider oil (monophasic) in a isotropic and saturated media, we can obtain a three equations system; for this, we begin with standard continuity equation and standard Darcy'slaw ,respectively(seeRef.…”

“…Since its forms are closer to the fractal geometry, the knowledge of this can be useful to develop models that allow us to better manage the wells. This work presents an approach in fractional derivatives for the triple porosity and triple permeability monophasic saturated model, based on the one proposed by Camacho et al [1,2] and generalized partially by Fuentes et al [3]. The main contribution is to consider the link between fractional equations and fractal geometry through the revision of Alexander-Orbach's conjecture [23], taken to the particular case.…”

A Triple-Continuum Pressure-Transient Model for a Naturally Fractured Vuggy Reservoir

“…In addition to the traditional double-porosity concept, a number of triple-porosity or triple-continuum models have been proposed [Closemann, 1975;Wu and Ge, 1983;Abdassah, and Ershaghis, 1986;Bai et al 1993;Wu et al, 2004;Kang et al 2006;Wu et al 2006] to describe flow through fractured rock. In particular, Liu et al [2003] and Camacho-Velazquez et al [2005] present several new triple-continuum models for single-phase flow in a fracture-matrix system that includes cavities within the rock matrix (as an additional porous portion of the matrix). In general, these models have focused on handling the heterogeneity of the rock matrix or fractures, e.g., subdividing the rock matrix or fractures into two or more subdomains with different properties.…”

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. Subsequently, the transient pressure of fractured well in fractured-vuggy reservoirs is investigated by Cai and Jia [6].…”