Controls on Reservoir Stress Path

A reduction in fluid pressure within a reservoir due to hydrocarbon production promotes changes in the effective and total stress distribution, not only within the reservoir but also in the surrounding strata. This stress evolution is the responsible of many problems encountered during production (e.g. surface subsidence, casing deformation, fault reactivation etc.). This work presents the results of an extensive series of 3D numerical hydro-mechanical coupled analyses that study the influence of reservoir geometry and material (reservoir and surrounding rock) properties on the stress path parameter values. It is shown how stress arching is more important when the reservoir Young’s modulus (Er) is lower than that of the bounding material (Eb), especially if the reservoir is small or elongated in shape. In such cases, the stresses will not significantly evolve in the reservoir, and stress evolution occurs in the over and side-burden. The higher the ratio Er/Eb, the less important the development of stress anisotropy is, although for extensive geometries the behaviour of the system tends to the theoretical oedometric case governed by the reservoir Poisson ratio independently of the ratio Er/Eb.