Interfacial reactions for the modification of flow in porous media

A new diverting agent was developed to control water production from oil reservoirs. It is an organic-based fluid that reacts to form a gel upon contact with an aqueous phase. The in-situ reaction is intended to reduce permeability during injection into water-bearing reservoir zones, thus inhibiting water production. However, experiments indicated that standard injection treatments also caused damage to oil-producing zones because of reaction with residual water. A modified treatment method was subsequently developed that provided highly selective permeability reduction in coreflood experiments.; A fundamental study of pore-scale flow mechanisms was performed in order to understand why, under certain conditions, the gel appears to have no effect on oil permeability while significantly lowering water permeability. Analysis of the fluid transport showed that this phenomenon occurs only when pretreatment oil pathways remain open following the gelation reaction. After water is introduced into the gelled medium, an irretrievable loss of oil permeability occurs because its altered morphology causes a redistribution of phases. Surprisingly, relative permeability experiments indicated that the overall effect of the gel was more damaging to oil conductivity than to water conductivity.; Because the oil-water interface is an integral part of the reaction sequence, the placement of gel is highly dependent on pore-scale events. To simulate the process, a model for flow through a disordered bed of spheres was developed. The model begins with a comprehensive description of the bed, and then uses a Delaunay tessellation to map the pore space onto a network. Flow through the bed is simulated by numerical solution of the Navier-Stokes equations at the pore scale; this information is then used in the network to calculate overall flow patterns.; An algorithm for immiscible displacement that accounts for the interplay between viscous forces, capillary forces, and gelation rate was incorporated into the model. It was observed that the loss of fluid conductivity due to a rapid in-situ gelation reaction depends not only on the injection rate and reaction rate, but also the immiscible displacement mechanism.