ABSTRACT:

Fractures shows strong stress sensitivity when the effective stress changes. Oil production causes the decrease of pore pressure and then leads to the change in subsurface stress. Re-open or closure of fractures bears significant influence on the fluid flow and oil production. The purpose of this work is to develop a general coupling between fluid flow equation and deformation of fractured media. To quantify the deformation of fracture during production, the geomechanical part used a porous elastoplastic damage model as its basis to investigate relationships between fracture dynamic change and pore pressure vary, and a numerical solution for the distribution of continuum damage variables is obtained by using the finite element method, and permeability of fractures was mathematically expressed with the damage variables. A model involving water-oil flow and fracture deformation was built to verify the coupled geomechanics-flow model and illustrate the nature of flow in a dynamic fractured formation. The corresponding damage evolution during production as well as the distribution of fracture permeability and formation pressure were obtained in the simulation. The results suggest that fractures gradually close and permeability decrease during production which can negatively impact the productivity. An uncoupled reservoir simulation may overestimate the oil production capacity of fractured reservoirs.

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