Change of in-situ stress regime by injection/production in isotropic and transversely isotropic media using fundamental solutions

Change of in-situ stress regime by injection/production in isotropic and transversely isotropic media using fundamental solutions

Original in-situ stresses of hydrocarbon reservoirs control the faulting regimes in the field. Any change of pore pressure due to injection or production into/from the reservoir cause changes in the in-situ stresses that should be considered precisely in reservoir geomechanics studies. In this paper, the induced stresses by injection/production into/from reservoirs are studied through utilizing available analytical solutions, deriving new Green’s functions, and transforming some closed-form solutions from thermoelasticity to poroelasticity for isotropic and transversely isotropic rocks. The analytical solutions are used for studying of the variation of in-situ stress regimes. Isotropic in-situ stress field and different faulting regimes as normal, reverse, and strike-slip having varying differences between the principal stresses are used for this study. The shape of the altered stress regimes are shown graphically and numerically for different stress regimes for both cases of having production or injection from/into the reservoir. The volumes of the changed regimes are numerically calculated and shown for better illustration of the influence of the original stress regime on the shapes and volumes of the altered regions. Effect of poroelastic parameters on this phenomenon is examined and discussed in detail. The effect of anisotropy on the stress regime change is also investigated by comparing the results of a transversely isotropic rock with the two bounding isotropic cases, isotropy of symmetric plane and the one normal to it. This work carries a lot of practical benefits; this is because alterations in the stresses may result changes in hydraulic fracturing design, refracing, fracture aperture and its conductivity. Reservoir compaction, wellbore failure, shearing and damage of the well are also some consequences of stress changes via production from reservoirs. The induced stresses by fluid injection and production in the reservoirs may also generate seismicity in the field; create large earthquakes, thereby having destructive effect on surface structures