New biopolymer for high-temperature profile control. Part 1. Laboratory testing

An extracellular polysaccharide produced by Alcaligenes bacteria has been crosslinked to form firm gels that are stable for long periods at elevated temperatures. The biopolymer can be gelled with multivalent ions such as Cr+3; it can also be gelled at the 2,000-to-4,000-ppm level without Cr+3 in high-salinity [ approximately 20% total dissolved solids (TDS)] brines. Gel samples have been stable for 2 years at 74 and 93°C. Gels could be formed over a wide pH range, but best long-term stability was achieved in the pH range of 7 to 8. A flow test of Alcaligenes biopolymer gel in Berea sandstone at 74°C showed that the gel gave a brine permeability reduction factor of 320.