Analysis of Gas Flow Behavior for Highly Deviated Wells in Naturally Fractured-Vuggy Carbonate Gas Reservoirs

Kongjie Wang,Lian Wang,Liang Zhang,Lan Wang,Caspar Daniel Adenutsi,Sen Yang,Zhiping Li

doi:10.1155/2019/6919176

Abstract

To improve the carbonate gas reservoir development and production, highly deviated wells (HDW) are widely used in the field. Production decline analysis of HDW is crucial for long-term gas reservoir development. However, it is a new challenge to incorporate the complex pore structure of naturally fractured-vuggy carbonate gas reservoirs and evaluate the production performance of HDW. This paper presents a semianalytical model to analyze the pressure and production behavior of HDW in naturally fractured-vuggy carbonate gas reservoirs, which consist of fractures, vugs, and matrix. The primary flow occurs only through the fracture and the outer boundary is closed. Introducing pseudopressure and pseudotime, the Laplace transformation, Fourier transformation, and its inverse and Stehfest numerical inversion were employed to establish a point source and line source solutions. Furthermore, the validity of the proposed model was verified by comparing a field data from the Arum River Basin in Turkmenistan. Finally, the effects of major parameters on the production decline curves were analyzed by using the proposed model and it was found that they had influences at different stages of gas production history and the sensitivity intensity of each parameter was different. With its high efficiency and simplicity, this semianalytical model will serve as a useful tool to evaluate the well production behavior for the naturally fractured-vuggy carbonate gas reservoirs.

Highlights

Carbonate gas reservoirs are widely distributed throughout the world
This paper presents a semianalytical model to analyze the pressure and production behavior of highly deviated wells (HDW) in naturally fractured-vuggy carbonate gas reservoirs, which consist of fractures, vugs, and matrix
The third stage was dominated by interporosity flow between fractures and vugs and this flow regime behaved with a “dip” on the pressure derivative curve

Summary

Introduction

Carbonate gas reservoirs are widely distributed throughout the world. In these carbonate reservoirs, the original gas in place (OGIP) and gas production account for more than half of gas reserves and production in the world [1]. A lot of triple-porosity models have been proposed through analytical, semianalytical, and numerical methods for analyzing gas flow in fractured-vuggy carbonate reservoirs. Al-Ghamdi and Ershaghi presented a triple-porosity dualpermeability model to characterize fracture heterogeneities, which considered discontinuous matrix and two continuous fracture networks, microfractures and macrofractures [15] Later, another triple-porosity dual-permeability model was proposed to characterize vuggy porosity, coexisting with matrix and fractures in carbonate reservoir by CamachoVelazquez et al [16]. Wu et al presented an analytical method for pressure transient analysis in fractured-vuggy carbonate reservoir that relied on a triple-continuum concept [17]. Meng et al proposed a semianalytical model of HDW for evaluating the pressure behavior which considered the stress-sensitive performance in fractured-vuggy carbonate gas reservoirs with composite systems [27]. Based on the proposed model, the effects of major parameters on production performance were studied

Physical Model

Mathematical Model

Results and Discussion

Conclusions

Calculation of Continuous Point Source Solution