Application of polymer gels for profile modification and sweep improvement of gas flooding

摘要

Early CO(sub 2) breakthrough can be a serious problem during miscible and immiscible CO(sub 2) flooding of reservoirs with heterogeneous formations. One potential method to reduce the problem of gas channeling is the use of a gel to restrict flow of fluids into the high-permeability zones. This study included evaluation of several different candidates for their potential as gelled polymer treatments for in situ profile modification. The objective of gel treatments is to restrict flow through fractures and high permeability zones without significantly damaging the adjacent oil productive zones. This involves injection of viscous polymer solution, hopefully into a high-permeability zone. In this study, layered sandpacks were used to show the effect of gelant mobility on gel penetration and placement. X-ray computerized tomography (CT) was used to visualize the flow path of the injected gelant and the location of gel placement. A conventional gel of xanthan and Cr(III) as a crosslinking agent was used for experimental model studies. The results of experimental model studies demonstrated the effects of viscous crossflow which may damage the oil productive strata. More specifically these studies of layered models showed that unless there is a very high-permeability contrast, such as a fractured zone, a considerable volume of viscous crossflow will occur with damage to oil productive strata. These results indicated the need for injection and placement of a low viscosity gelant prior to gelation.