Pseudo-Steady-State Parameters for a Well Penetrated by a Fracture with an Azimuth Angle in an Anisotropic Reservoir

Guoqiang Xing,Hua Li,Mingxian Wang,Wenqi Zhao,Jiangyan Dong,Shuhong Wu

doi:10.3390/en12122449

Abstract

Many oil wells in closed reservoirs continue to produce in the pseudo-steady-state flow regime for a long time. The principal objective of this work is to investigate the characteristics of two key pseudo-steady-state parameters—pseudo-steady-state constant (bDpss) and pseudo-skin factor (S)—for a well penetrated by a fracture with an azimuth angle (θ) in an anisotropic reservoir. Firstly, a general analytical pressure solution for a finite-conductivity fracture with or without an azimuth angle in an anisotropic rectangular reservoir was developed by using the point-source function and spatial integral method, and two typical cases were employed to verify this solution. Secondly, with the asymptotic analysis method, the expressions of pseudo-steady-state constant and pseudo-skin factor were obtained on the basis of their definitions, and the effects of permeability anisotropy, fracture azimuth angle, fracture conductivity and reservoir shape on them were discussed in detail. Results show that all the bDpss-θ and S-θ curves are symmetric around the vertical line, θ = 90° and form a hump or groove shape. The optimized fracture direction in an anisotropic reservoir is perpendicular to the principal permeability axis. Furthermore, a new formula to calculate pseudo-skin factor was successfully proposed based on these two parameters’ relationship. Finally, as an application of pseudo-steady-state constant, a set of Blasingame format rate decline curves for the proposed model were established.

Highlights

Considering that steady state condition rarely occurs in reservoirs, pseudo-steady-state (PSS)flow regime is one of the most important regimes for all closed reservoirs [1,2]
Flow regime is one of the most important regimes for all closed reservoirs [1,2]. This regime may last for a long time, and many oil or gas wells continue to produce in this regime; a considerable productivity may be recovered from these reservoirs. It is of great significance for a closed reservoir to investigate its characteristics in the PSS flow regime
Due to the defects existed in the proposed approaches, the primary purpose of this work is to find a new way to deal with permeability anisotropy for a finite-conductivity fracture with an azimuth angle in an anisotropic rectangular reservoir and further to investigate its corresponding pseudo-steady-state parameters

Summary

Introduction

Considering that steady state condition rarely occurs in reservoirs, pseudo-steady-state (PSS)flow regime is one of the most important regimes for all closed reservoirs [1,2]. This regime may last for a long time, and many oil or gas wells continue to produce in this regime; a considerable productivity may be recovered from these reservoirs It is of great significance for a closed reservoir to investigate its characteristics in the PSS flow regime. Pseudo-steady-state constant and pseudo-skin factor are two key parameters to reflect upon the property of PSS flow regime. Based on the pseudo-skin factor for a uniform-flux inclined fracture presented by Cinco-ley [8], Jia et al (2016) discussed the effect of inclination angle, fracture conductivity and permeability anisotropy on the pseudo-skin factor for a finite-conductivity inclined fracture connected to a slanted wellbore [12] Their conclusions provide a theoretical basis for optimizing the well pattern and designing the reservoir stimulation

Objectives

Results

Conclusion