Well Testing Model of Multiple Fractured Horizontal Well with Consideration of Stress-Sensitivity and Variable Conductivity in Tight Gas Reservoirs

Zhongwei Wu,Yingfei Sui,Peifeng Jia,Wenhao Tang,Zhen Wang,Chuanzhi Cui

doi:10.1155/2018/1693184

Abstract

Multiple fractured horizontal wells have been widely used to develop unconventional tight gas reservoirs. Currently, many well testing models were established to study the performance of fractured horizontal wells in tight gas reservoirs. However, none of these models thoroughly takes stress-sensitivity of natural fractures and variable conductivity of artificial fractures into consideration. Based on the consideration of stress-sensitivity of natural fractures and variable conductivity of artificial fractures, a novel well testing model for fractured horizontal well in tight gas reservoirs is proposed. And the semianalytical solution of this new model is obtained by dividing the artificial fracture into different segments under the integrative methods of Laplace transformation, point source function, perturbation theory, superposition principle, and Stehfest numerical inversion. After validation, the semianalytical solution is consistent with that of Zerzar’s model (2004). Also, typical pressure and pressure derivative curves are plotted. According to typical curves, seven regimes can be derived, namely, bilinear flow, linear flow, early-time pseudoradial flow, biradial flow, intermediate-time pseudoradial flow, and pseudo-steady state interporosity flow, and late-time pseudoradial flow can be identified. In addition, this paper analyzes the impact on pressure and pressure derivative curves exerted by variable conductivity and stress-sensibility. The results show that variable conductivity mainly affects the early flow regimes, including bilinear flow, linear flow, and early-time radial flow, while the stress-sensitivity mainly affects the later flow regimes, including intermediate-time pseudoradial flow, pseudo-steady state interporosity flow, and late-time pseudoradial flow. The typical curves will ascend with the increasing of stress-sensitivity coefficient. The research provides a method for precise prediction of formation parameters and has a significant impact on the tight gas reservoir development.

Highlights

The technology of multiple fractured horizontal well has become the mainstream method for exploiting tight gas reservoirs [1,2,3,4]
The pressure analysis of multiple fractured horizontal wells has a great significance to the development and optimization of tight gas reservoirs
The natural fracture has developed in tight gas reservoirs [5, 6]

Summary

Introduction

The technology of multiple fractured horizontal well has become the mainstream method for exploiting tight gas reservoirs [1,2,3,4]. The stress-sensitivity of the tight gas reservoir was neglected and the conductivity of hydraulic fracture was a constant. During the establishment of the coupling model, finite conductivity of hydraulic fractures and stress-sensitivity of the reservoir were taken into account. They did not take the effect of variable conductivity of hydraulic fracture on well performance into consideration. Zhang et al [19] and Yin et al [20] established a performance model of horizontal wells with multiple fractures in a tight oil reservoir They did not take the stress-sensitivity and variable conductivity into consideration. The effects of relevant parameters are discussed, especially for the variable conductivity of artificial fractures

Physical Model

Mathematical Model

Model Validation

Results and Discussion

Conclusions