A Computational Scheme for Evaluating the Stress Field of Thermally and Pressure Induced Unconventional Reservoir

Yao Fu,Xiangning Zhang,Xiaomin Zhou,Shiyuan Zhan

doi:10.2113/2021/1164947

Yao Fu, Xiangning Zhang + Show 2 more

Open Access

https://doi.org/10.2113/2021/1164947

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Journal: Lithosphere	Publication Date: Sep 21, 2021
Citations: 1	License type: CC BY 4.0

Affiliation: Zhejiang Industry Polytechnic College

Abstract

Abstract The fluid flow connecting the hydraulic fracture and associated unconventional gas or oil reservoir is of great importance to explore such unconventional resource. The deformation of unconventional reservoir caused by heat transport and pore pressure fluctuation may change the stress field of surrounding layer. In this paper, the stress distribution around a penny-shaped reservoir, whose shape is more versatile to cover a wide variety of special case, is investigated via the numerical equivalent inclusion method. Fluid production or hydraulic injection in a subsurface resource caused by the change of pore pressure and temperature within the reservoir may be simulated with the help of the Eshelby inclusion model. By employing the approach of classical eigenstrain, a computational scheme for solving the disturbance produced by the thermally and pressure induced unconventional reservoir is coded to study the effect of Biot coefficient and some other important factors. Moreover, thermo-poro transformation strain and arbitrarily orientated reservoir existing within the surrounding layer are also considered.

Highlights

The International Energy Agency projections indicate that an increasing supply gap for liquid fuels will arise if discovery and investment in new fields are unable to meet the urgent requirements with the rapidly increasing consumption of resources
Results are displayed as the ratio of Ematrix/Ereservoir; the Von Mises stress reaches the maximum points at x1/a1 = −1, 1 when Ematrix = 5/3Ereservoir and minimum points at x1/a1 ≤ −1, or ≥ 1
Fluid production or hydraulic injection in a subsurface resource would like to change the pore pressure and temperature within the reservoir, which generally induces the alteration of stress distribution within and around the reservoir

Summary

Introduction

The International Energy Agency projections indicate that an increasing supply gap for liquid fuels will arise if discovery and investment in new fields are unable to meet the urgent requirements with the rapidly increasing consumption of resources. The fluid flow connecting the fracture and surrounding rocks, heat transport, and temperature changes within the resource may significantly disturb the stress fields and deformation of the unconventional oil reservoirs including the shale and tight sand reservoir. The problems of two interacting ellipsoidal inclusions and inhomogeneities with arbitrary orientation are solved to determine the elastic stress and strain components using Eshelby’s technique, and such method can be extended to discuss the pressure induced fracture [16, 17]. The stress fields around a penny-shaped reservoir with thermo-porous eigenstrains in a full space are investigated via the numerical equivalent inclusion method. Parametric studies and examples on the Biot coefficient, distribution of a reservoir, effect of linear thermal expansion, temperature changes, pore pressure fluctuation, and elastic stress disturbance are provided.

The Eshelby Model

Discussion

Conclusions