RESEARCH ARTICLE


Numerical Simulation of Fracture Permeability Change in Production of Pressure-sensitive Reservoirs with In-situ Stress Field



Shaohua Gu1, *, Yunqing Shi1, Zhangxin Chen2
Petroleum Exploration and Production Research Institute of Sinopec, Beijing 100083, China.


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© 2015 Gu et al.;

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Correspondence: * Address correspondence to this author at the Petroleum Exploration and Production Research Institute of Sinopec, Beijing 100083, China; Tel: +86 010 82312121; Fax: 010-82312751; E-mail: cc0012@126.com


Abstract

In pressure sensitive reservoirs, interaction effects among the porous media flow field, the fracture field and the stress field can cause some specific flow characteristics entirely different from those in conventional reservoirs. Dynamic fracture behavior is one of them, which generates a change in the value of fracture aperture and even a variation in the anisotropy of permeability. In this paper, we focus on the dynamic behavior of fractures and some affecting factors, including driving pressure and in-situ stress. Numerical discrete fracture network (DFN) models are built and solved by the finite element method to investigate what the range-ability the fracture presents and what impact these affecting factors have. In these mathematical models, both dynamic fractures and the fluid-solid coupling are taken into account, and a stress-strain model, a flow field model and a fluid-solid coupling model are included. Based on the models, the variation of fracture aperture in pressure sensitive reservoirs is studied and the results show that a different direction and connectivity of fractures lead fracture dilation to varying degrees as pressure changes so that the idea of anisotropic fracture porosity is proposed for reservoir scale simulation. The study also indicates that the drop of formation pressure determines the conductivity of fractures and anisotropy of permeability but just has a slight impact on the direction of principal permeability. Finally, the study shows the interaction of the in-situ stress pressure and the fracture field.

Keywords: Anisotropy, DFN model, fractured reservoir, in-situ stress, pressure sensitive.