Fluid-Solid Coupling Analysis on Evolution of In-Situ Stress Field by Water Injection in Oilfield

Water injection in oilfield may break initial balance of reservoir and lead to re-distribute of stress and deformation of strata. For further research of the evolution characteristics of in-situ field by water injection, the influence on reservoir by water injection was analyzed and different variables were set to study the effects of depth, injection-withdraw ratio and elastic modulus on strain and stress of strata based on fluid-solid coupling theory. Research shows that: As the water injection, the formation pressure around injection well is greater than that of the production well and the effective stress around injection well is less than that of production well. The deeper the formation is, the smaller the normal strain and vertical displacement are. Besides, the largest shear strain is on the top of reservoir, while the smallest is in central reservoir and different injection-withdraw ratios have significant influence on formation pressure. Elastic modulus mainly influences the deformation of the formation and deformation size is negatively related to the elastic modulus. This study provides a reference for casing damage under the effect of water injection.