Fracturing operations consume relatively large amounts of fresh or groundwater, especially in the area of unconventional resources where multi-stage fracturing is required to obtain an economical production rate and improve recovery. In an attempt to conserve groundwater, treated sewage effluent (TSE) has been evaluated and optimized for fracturing treatments to provide the required transport property for the proppant and not induce formation damage by maintaining compatibility with formation brine. Extensive laboratory work has been conducted including viscosity measurements, compatibility testing, and a microbial study to optimize an TSE-based fracturing fluid for unconventional operations. Based on laboratory recommendations, the TSE-based fracturing fluid has been applied successfully on well-A.

Twenty stages of unconventional proppant fracture stimulation utilizing the Plug and Perf (P-n-P) technique across the carbonate source rock have been applied successfully. Two base fluids, freshwater and TSE, were used to evaluate the effectiveness of TSE as a substitute for the freshwater in unconventional fracturing operations. Each water was used in 10 stages. The post-fracturing production results of well-A showed comparable results with the offset wells treated only with freshwater-based fracturing fluids. The pressure logging tests (PLT) conducted on this well confirmed that contribution of intervals treated with TSE-based fracturing fluid was comparable with those treated with fresh water-based fracturing fluid. There was no evidence of scaling issues during the flowback period for both fluid systems. Microbial evaluation of water samples collected during the flowback of well-A showed no presence of bacteria in these samples. This paper will discuss the laboratory work and the field application of TSE-based fracturing fluid.

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