S5: Peracetic Acid (PAA): An environmentally safe biocide for water treatment during hydraulic fracturing application

Shale gas in the US has become an important source of natural gas. Driven by the development of new technologies such as hydraulic fracturing and horizontal drilling, shale gas has led to increases in reserves of US natural gas. Hydraulic fracturing is the process that increases of fractures in the formation by the injection of chemicals and water at high pressure. Due to the large quantities of water needed in the process, many hurdles arise around water treatment and reuse. First, the water must be treated to avoid the introduction of microorganisms in the formation, which can result in problems such as reservoir souring, biofouling and microbiologically-influenced corrosion (MIC). Second, to reduce the demand for fresh water, the flowback water must be cleaned up and reused in subsequent applications. We have developed an improved formulation of the oxidizing biocide peracetic acid (PAA) to address these critical needs. To understand the potential use of PAA in fracturing application, we conducted tests in laboratory and field conditions and found that this chemistry showed superior results compared to other conventional biocides (glutaraldehyde, THPS, etc). These include: faster and persistent microbial kill, water cleanup and solids dropout. We also found that PAA had no adverse effects on chemistries present in the frac fluids, such as friction reducers and scale inhibitors. Additionally, PAA is a “green” chemistry as it breaks down into innocuous components - water and vinegar. Altogether, PAA represents an efficient and environmentally safe option for treatment of frac fluids during hydraulic fracturing.