Injectivity and Gravity Override in Surfactant-Alternating-Gas Foam Processes

Abstract

Abstract Surfactant-alternating-gas (SAG) foam processes can in principle combine high gas injectivity with low mobility at the front of the foam bank. Such a process can give the appearance of extremely shear-thinning behavior, in that the pressure gradient is remarkably low near the well. However, this appearance is due to the effects of declining water saturation near the well, not to the effects of high near-well flow rates on foam mobility. Preliminary simulation results suggest that as long as mobility is low in a region away from the well, high gas mobility near the well need not lead to gravity override. Indeed, since increased injectivity allows higher injection rates and thereby increased flow rates and pressure gradients away from the well, increased mobility near the well may help to reduce the risk of gravity override.