Chromium (III) Propionate: A Crosslinking Agent for Water-Soluble Polymers in Hard Oilfield Brines

Summary Reservoir heterogeneity and channeling have limited the success of many EOR projects because the injected fluids are preferentially transported through the path of least resistance. Current technology uses water-soluble polymers gelled with a suitable crosslinker to block, either partially or totally, channels and high-permeability zones. Most of the known gel systems are not usable in hard brines because the crosslinking chemicals are either incompatible or unstable in those brines. This reports on the new chromium (III) (Cr+3) propionate gel system that was found suitable for in-depth, as well as near-well, gel treatments in both fresh water and hard brines. Laboratory coreflood testing of this gel system in various brines with hardness (calcium) levels up to 14,000 ppm resulted in high, long-lasting residual resistance factors (RRF’s). The stability and performance of Cr propionate in hard brines will extend gel treatments to reservoirs that have been excluded from consideration because fresh water was not available.