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UBC Theses and Dissertations

Optimization of hydraulic fracturing wastewater management using hybrid multi-objectives linear programming Shamloo, Nazila


Hydraulic fracturing (HF) generates a large volume of wastewater with a high level of contaminants during unconventional oil and gas production. HF wastewater management has emerged to support sustainable economic development in North America. In this study, a novel hybrid multi-objective linear programming (HMOLP) model was developed to optimize HF wastewater management operations. The objectives of this model were to minimize overall wastewater treatment cost, environmental impacts, and deviations from different goal constraints, simultaneously. The main goal constraints were the maximum concentration of total dissolved solids (TDS) that can be treated, and their maximum concentration in the treated wastewater for reuse or discharge. Onsite treatment, deep well injection, and offsite treatment were considered as HF wastewater management strategies. The developed model was applied to two case studies that used actual ranges of data for 31 weeks of operations. As results, the model identified the optimal treatment strategies in which the volume of HF wastewater to be transported to each management strategy, and the volume of the returned treated wastewater for reuse were determined. The model selected onsite treatment for reuse in subsequent fracking as the optimal strategy in those weeks that all constraints were satisfied. When the volume of HF wastewater was lower than that capacity of onsite treatment, the model recommends two strategies as optimal. The volume equal to the capacity of onsite treatment, i.e., 3000 bbl (barrel) of HF wastewater was delivered to the onsite treatment, and the remaining volume was delivered to the offsite treatment. When there was no water demand for the next fracking, the model selected deep well injection rather than treatment options. A sensitive analysis was conducted by using weighting objectives and the conditions with different partially pre-filled storage. Environmental impacts had significant impacts on the optimal strategies selection. Similarly, 0%, 30%, and 50% pre-filled storage did not affect the selection of optimal strategies. However, due to an increasing TDS level over time, the optimal strategy selection might be different for other case studies. The prepared model can be used for similar problem to optimize wastewater management operation in unconventional oil and gas production.

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