New flow model for the triple media carbonate reservoir

Abstract

A new flow model in triple media carbonate reservoir is established. There exists a triple total system including the matrix, fracture and vug subsystem, and the three subsystems are relatively independent in physical properties; in the process of oil flow, the inter-porosity flow of the vug subsystem to fracture subsystem would occur and the interporosity flow of the matrix subsystem to fracture subsystem would also occur and ignore the inter-porosity flow between the matrix subsystem and vug subsystem. Compared with the traditional model (the inter-porosity flow of vug to fracture is pseudo-steady), the new model considers the unsteady inter-porosity flow, based on the hypothesis that the shape of vug is spherical. The new model is illustrated and solved, and the standard type curves are drawn up, so the process and characteristics of flow are analysed thoroughly, and it is found that the new-style type curves in shape and characteristics are evidently different from the type curves of traditional model. The research would not only deepen the understanding of flow law but also enrich the theoretical models for carbonate reservoir. The research results on this new model could be applied to a real case study.

Flow Modeling of Well Test Analysis for Porous–Vuggy Carbonate Reservoirs

“…An unsteady interporosity flow (vug pressure not only relates to time, t, but also to radial spherical coordinate, r , causing a pressure drop in vug) is considered. The pressure distribution in a vug is spherically symmetric (Nie et al 2011(Nie et al , 2012a.…”

“…The flow problem in carbonate reservoirs has been well researched: (i) theory and applications on dual porosity flow model for well test analysis of fractured reservoirs (Al-Ghamdi and Ershaghi 1996;Bourdet and Gringarten 1980;Braester 1984;Bui et al 2000;Izadi and Yildiz 2007;Lai et al 1983;Liu et al 2003;Jalali and Ershaghi 1987;Rasmussen and Civan 2003;Wijesinghe and Culham 1984;Wijesinghe and Kececioglu 1985) and (ii) theory and applications on triple porosity flow model for well test analysis of fractured-vuggy reservoirs (Bai and Roegiers 1997;Camacho-Velázquez et al 2006;Nie et al 2011Nie et al , 2012aPulido et al 2006;Veling 2002;Wu et al 2004Wu et al , 2007Wu et al , 2011. Both the medium connected to the wellbore and the interporosity of fluid from the matrix or vug systems into the fracture system were considered as the fracture system.…”

“…Pseudo-steady interporosity flow characteristics were commonly assumed by considering arbitrarily shaped matrix blocks and vugs (Camacho-Velázquez et al 2006;Wu et al 2004Wu et al , 2007Wu et al , 2011. Unsteady interporosity manner was assumed by considering spherical shaped matrix blocks and vugs (Nie et al 2011(Nie et al , 2012a. It is hard to distinguish the difference between separate vug and connected vug systems by using well test analysis.…”

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

“…(18) can be expanded by discrete approximate method [30]. (19) Where △x=L fD /n, x D,j is the center of the jth segment, x D , i is the starting point of ith segment, x D , i+1 is the end point of i th segment. n equations for n discrete segments can be established.…”

“…According to above mentioned models in fractured-vuggy carbonate reservoirs, two main models are used to describe and study the flow process in fractured-vuggy carbonate reservoirs: (1) triple porosity and single permeability model [15], [19]. The model considers the vug system as a continuum medium, treats fracture system as pathways directly connected to the wellbore, and considers the matrix and vug systems connect to the fracture system.…”