The unique and reactive chemistry of acrolein enables a 3-fold approach to oilfield problems stemming from sulfate reducing bacteria (SRB): 1) it is an effective biocide, 2) it scavenges H2S, and 3) it dissolves iron sulfide.
In this study, the utility of acrolein for remediation of problems with SRB and biogenic sulfides in a gas plant water disposal system at an facility near Mobile, Alabama is presented. The disposal system, designed to handle produced water from offshore, process water from gas plant operations, and surface water drainage within the plant, was losing capacity due to iron sulfide fouling of the surface equipment and plugging of the disposal wells.
Bacterial monitoring indicated that SRB originating from the drain water had become established in the tanks and flowlines. These SRB were generating 8-10 ppm dissolved H2S that was ultimately responsible for the iron sulfide formation. The iron sulfide resulted in poor water quality (Millipore® rates = 200-300 ml/5 min), tank fouling, filter plugging, injection line scaling, and loss of injectivity due to near well bore damage in the disposal wells.
The treatment design consisted of 1) initial remediation of injection wells by acrolein squeeze stimulations using a coiled tubing unit, 2) removal of iron sulfide pads from the tankage and iron sulfide build up in the disposal lines, and mitigation of SRB populations via batch treatments with acrolein, and 3) preventive maintenance using a continuous and batch treatment program with acrolein.
Immediately following squeeze treatment of the disposal wells, a 30% increase in capacity was observed. The topside treatment program has resulted in a 400 to 500% improvement in Millipore® rates, decreased levels of SRB, greater than 90% decrease in soluble H2S and a 65% decrease in filter replacements. Overall benefits of the program include acceptable injection rates and pressures and reduced operating costs through decreased filter changes, remedial expenses to maintain the disposal wells, and water trucking expenses.