Recycling Fracturing Flowback Water for Use in Hydraulic Fracturing: Influence of Organic Matter on Stability of Carboxyl-Methyl-Cellulose-Based Fracturing Fluids

Recycling oilfield wastewater for hydraulic fracturing requires a good understanding of the water chemical characteristics and how these interact with the fracturing fluid. The viscosity and rheological properties of fracturing fluids affect proppant placement, length and width of fractures, fracture conductivity, and, consequently, the success of the treatment. The objective of the research described here was to understand if dissolved organic matter (DOM) at high concentrations influences subsequent fracturing with a gelled fluid. Experimental studies were conducted on four types of water: (1) model water with low DOM, (2) recycled water from an industrial-treatment facility (medium DOM), (3) untreated early-time flowback (ETFB) water (high DOM), and (4) untreated produced water (high DOM). A low-pH, zirconium-crosslinker-gelled fluid at 200 degrees F was examined in the study. All three water samples that had significant levels of organic matter [total organic content (TOC) > 1000 mg/L] exhibited lower peak viscosities and more-rapid viscosity decay than the model water without organic matter. The destabilizing influence of organic matter on carboxyl methyl cellulose (CMC) gelled fracturing-fluid viscosity is thought to be caused by secondary crosslinking of the short-chain polymer residuals in the flowback, resulting in lower initial viscosity and stability.