Abstract
Bacterial contamination of fracturing fluids leads to a number of serious problems in the oil field. If the fracturing fluids are poorly treated or untreated, sulfate-reducing bacteria (SRB) and acid-producing bacteria (APB) can become established downhole, in production lines, gas / fluid separation, storage equipment, and in the gas gathering and transportation systems. This may result in hydrogen sulfide production, iron sulfide production and microbially influenced corrosion (MIC). Many of these fracturing fluids contain polyacrylamide or sugar-based polymers and other organic compounds which serve as food sources for bacteria. As a consequence of the water volume required for the fracturing process, the water used for preparation of these fluids is obtained from rivers, lakes, or oil field wastewater and is heavily contaminated with bacteria. This paper presents a case history discussing the background survey of various fracturing water sources, the biocide selection process, bacterial mitigation program implementation, monitoring and optimization of a Barnett Shale fracturing biocide program. Various biocides were tested including glutaraldehyde, a glutaraldehyde/quaternary ammonium compound blend, isothiazolin, tetrakishydromethyl phosphonium sulfate (THPS), 2,2-dibromo-3-nitrilopropionamide, and bronopol. THPS consistently performed well providing both quick kill of aerobic, fermentative, and sulfate-reducing bacteria and long-term preservation of the produced fluid. The glutaraldehyde and glutaraldehyde blends did not perform well on the general aerobic and acid-producing bacteria.
