Transporting waterflood mobility control agents to high permeability zones

摘要

A method for improving the a real sweep efficiency of a waterflood process is described. Reservoir heterogeneity results in the waterflood being diverted to the thief zones, bypassing much of the in- place hydrocarbon fluids. Existing remedial options are sensitive to water chemistry and temperature and are mostly effective near the wellbore. The unique advantages of this process is that it is insensitive to the water phase, in-depth in its placement, and can be triggered by pressure change which no other existing process offers. The process works by dispersing a low viscosity gas like plugging solution in the injected water phase, the dispersed plugging solution phase being a combination of some solvent phase like carbon dioxide, or light hydrocarbons, or mixtures of the same, in which a very high viscosity solute like a polymer is dissolved the composition of the dispersed plugging solution phase can be adjusted so that it is essentially homogeneous when injected with the aqueous phase and offers no additional resistance to the injection or movement of the water phase through the reservoir. However, as the water phase with dispersed plugging solution penetrates the reservoir rock, increasing temperature or decreasing pressure, or a combination of the two causes the plugging solution phase to destabilize releasing a gas and leaving behind a liquid like phase of increasing viscosity. This dispersed phase of increasing viscosity can be expected to plug the pore throats of the reservoir rock through which the water phase is flowing, and this increased resistance to flow will cause the waterflood to bypass the plugged zones to access larger volumes of the reservoir rock.