Reinjection of Produced Water with High Salinity After Applying a Novel Treatment Method
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AbstractThis study investigates a novel method to reduce TDS in produced water to enable safe and effective reuse in hydraulic fracturing. In particular, we test whether evaporative technology can effectively separate dissolved solids from high-TDS wastewater produced in abundance in oil fields.Experiments were conducted with distilled water (E1) and produced water (E2), among which the distilled water experiment served as a control experiment for comparison purposes. Produced water (PW) samples were taken from the Southern Midland Permian Basin. An evaporative air cooler was used for the experiments. We replaced the cellulose filters in the air cooler with Pozzolan filters as the latter is resistant to corrosion and can be easily regenerated. The filter was wet continuously by the water sample stored in the reserve tank of the evaporative cooling unit. Each experiment was run for 4 hours. To determine the systems cooling efficiency, we measured inlet and outlet ambient temperatures, wet-bulb temperatures, dew point temperatures, and relative humidity every hour using a temperature humidity meter. In addition, the water samples were characterized before and after each experiment by measuring total dissolved solids (TDS), pH, particle size, and zeta potential.Our experiments showed that E1 had a cooling efficiency of 21% while E2 had 16% in the laboratory environment, which does not have continuous airflow in and out like on the wellheads in an oilfield. Hence, we expect higher efficiencies in an oilfield. The reduction in cooling efficiency from E1 to E2 is primarily attributed to the precipitation of the suspended solids on the filter. Therefore, we recommend removing suspended solids from the water before filtering it through the evaporative cooling unit. In addition, we observed that the amount of water treated through the process was slightly less for E2 (35% of the initial volume) than E1 (40% of the initial volume). We believe this treatment efficiency can increase further if the experiments are conducted on the wellhead rather than in a laboratory. Furthermore, we observed a reduction in particle size and an increase in zeta potential in the reserve water post-experiment. In other words, the TDS was mainly eliminated and remained in the untreated water body, while the treated water contained significantly less amount of TDS with higher stability.We prove that evaporative cooling is a novel method for low-cost TDS reduction. As a result, it can be instrumental in solving the decade-long problem of large volumes of high TDS wastewater produced during hydraulic fracturing, particularly in the Permian Basin.
