| Gelled polymer systems are widely used in petroleum production to modify permeability of reservoir rock and physically block flow through high permeability zones. To achieve in-depth permeability modification, gelled polymer systems must be injectable into the reservoir as a low viscosity gelant and then triggered in situ to form high viscosity gel. Many of the gelled polymer systems currently available use toxic or regulated compounds to trigger the delayed gelation reaction. More environmentally friendly gelled polymer systems which eliminate the need for toxic chemicals are desired.;This research examined a novel technique of using metabolism of alkaliphilic bacteria to trigger curdlan-type biopolymer gels. Two strains of alkaliphilic bacteria were isolated from Soda Lake in the Mojave Desert in California. Both isolates were mesophilic, halotolerant, and obligately alkaliphilic. Phylogenetic analysis using 16S rDNA sequences was used to identify the isolates. Strain SL-1A, a facultative, gram-positive, coccobacilli, grouped closest to a branch of carnobacteria. Based on the alkaliphilic and halotolerant nature of strain SL-1A, it was classified as a new Carnobacterium sp. Strain SL-2A, a spore-forming, gram-variable, anaerobe was placed with a group of alkaliphilic Bacillus sp. Because the genus Bacillus is categorically aerobic, strain SL-2A was classified as a new Bacillus sp.;When the alkaliphilic isolates were used to trigger the biopolymer gel, gelation time was inversely proportional to inoculum concentration and was delayed up to 285 hours after inoculation. Treatment of Berea sandstone cores with the microbially gelled biopolymer system decreased brine permeability by more than 99 percent. In parallel corefloods the polymer system was able to block high permeability brine channels and divert increased flow into low permeability zones. Permeability modification with the polymer system improved sweep efficiency and improved oil recovery above waterflooding alone. The oil recovery efficiency in coreflood experiments was 26 to 30 percent for permeability modification alone and 56 percent for permeability modification combined with an alkaline-surfactant-polymer flood. The use of the polymer system for environmental remediation was evaluated in native soil cores. Hydraulic conductivity of soil was reduced by three to four orders of magnitude with the polymer system. |
