A Modified Numerical Model for Production-Induced Stress in Refracturing Gas Well

Abstract

Technical key points of deflection refracturing are the selections of the most reasonable refracturing time and parameters, based on the changes of original geostresses. Production-induced stress due to pore pressure change is one of the dominant factors influencing geostress reorientation; however, displacement discontinuity of the fracture surface has hardly been considered in numerical models for production-induced stress both at home and abroad; also the solution procedures of the present models are relatively complicated, and the convergences are relatively poor. In this paper, based on poroelasticity theory and seepage mechanics, a modified fluid–structure interaction model for production-induced stress in refracturing gas well was established and solved by the hybrid method of displacement discontinuity method (DDM) and finite difference method (FDM), and then the distribution characteristics of the production-induced stress with time and space were obtained. Calculations indicate that decreasing range of maximum horizontal principal stress is greater than that of minimum horizontal principal stress due to pore pressure reduction, and this is a major factor leading to stress reorientation. The higher the production time and production pressure drop are and the smaller the original horizontal stress difference is, the easier it will be to form stress reorientation area. Meanwhile, shear stress around the fracture increases due to the fluid–structure interaction during production, which helps increase the complexities of new fractures. The new numerical model for production-induced stress takes discontinuous displacement of the fracture section into consideration. In addition, the calculation method is simple and has satisfactory convergence. The study results have certain significance to improve the success rate of refracturing in oil gas well by providing scientific guidance for well and layer selection and construction time selection.

Copyright 2017, Shaanxi Petroleum Society.

This paper was prepared for presentation at the 2017 International Field Exploration and Development Conference in Chengdu, China, 21–22 September 2017.

This paper was selected for presentation by the IFEDC&IPPTC Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the IFEDC&IPPTC Committee and are subject to correction by the author(s). The material does not necessarily reflect any position of the IFEDC&IPPTC Committee, its members. Papers presented at the Conference are subject to publication review by Professional Committee of Petroleum Engineering of Shaanxi Petroleum Society. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of Shaanxi Petroleum Society is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of IFEDC&IPPTC. Contact email: paper@ifedc.org or paper@ipptc.org.