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Título: Water Management in Shale Gas: A Perspective from the Cooperative Games Theory
Autor/es: Ruiz-Femenia, Rubén; Salcedo Díaz, Raquel; Caballero, José A.
Título: Combining Forward and Reverse Osmosis for Shale Gas Wastewater Treatment to Minimize Cost and Freshwater Consumption
Autor/es: Salcedo Díaz, Raquel; Ruiz-Femenia, Rubén; Carrero-Parreño, Alba; Onishi, Viviani C.; Reyes-Labarta, Juan A.; Caballero, José A.
Resumen: One of the challenges for the future of the shale gas production industry is the water management due to the large demand of water for wells drilling and fracturing and the high volumes of liquid effluent produced. On-site treatment is a convenient option for the reuse of the shale wastewater as drilling water for subsequent wells, which simultaneously reduces the freshwater consumption and the waste volume. While conventional desalination technologies are suitable for the treatment of flowback water, they are not appropriate for the hypersaline produced water, which is typically disposed into underground injection wells. In this work, we propose a mathematical model to address the optimal design of an on-site treatment for both flowback and produced waters, combining reverse and forward osmosis, to simultaneously minimize the freshwater consumption and the specific cost of the fracturing water. The results obtained show a clear trade-off between both objectives and highlight the potential of the proposed technology combination to give an environmentally friendly solution to the shale gas produced water.
Título: Optimal Shale Gas Flowback Water Desalination under Correlated Data Uncertainty
Autor/es: Onishi, Viviani C.; Ruiz-Femenia, Rubén; Salcedo Díaz, Raquel; Carrero-Parreño, Alba; Reyes-Labarta, Juan A.; Caballero, José A.
Resumen: Optimal flowback water desalination is critical to improve overall efficiency and sustainability of shale gas production. Nonetheless, great uncertainty in well data from shale plays strongly hinders the design task. In this work, we introduce a new stochastic multiscenario optimization model for the robust design of desalination systems under uncertainty. A zero-liquid discharge (ZLD) system composed by multiple-effect evaporation with mechanical vapor recompression (MEE-MVR) is proposed for the desalination of high-salinity shale gas flowback water. Salinity and flowrate of flowback water are both considered as uncertain design parameters, which are described by correlated scenarios with given probability of occurrence. The set of scenarios is generated via Monte Carlo sampling technique from a multivariate normal distribution. ZLD operation is ensured by the design constraint that allows brine concentration near to salt saturation conditions for all scenarios. The stochastic multiscenario nonlinear programming (NLP) model is optimized in GAMS, through the minimization of the expected total annualized cost. Risk analysis based on cumulative probability curves is performed in the uncertain search space, to support decision-makers towards the selection of more robust ZLD desalination systems applied to shale gas flowback water.
Descripción: Presentation at the 27th European Symposium on Computer-Aided Process Engineering (ESCAPE-27), Barcelona, 2017, 1-5 October.
Título: Holistic Planning Model for Sustainable Water Management in the Shale Gas Industry
Autor/es: Carrero-Parreño, Alba; Reyes-Labarta, Juan A.; Salcedo Díaz, Raquel; Ruiz-Femenia, Rubén; Onishi, Viviani C.; Caballero, José A.; Grossmann, Ignacio E.
Resumen: To address water planning decisions in shale gas operations, we present a novel water management optimization model that explicitly takes into account the effect of high concentrations of total dissolved solids (TDS) and temporal variations in the impaired water. The model comprises different water management strategies: (a) direct wastewater reuse, which is possible because of new additives tolerant to high TDS concentrations but at the expense of increasing the costs; (b) wastewater treatment, separately taking into account pretreatment, softening, and desalination technologies; and (c) the use of Class II disposal sites. The objective is to maximize the “sustainability profit” by determining the flowback destination (reuse, degree of treatment, or disposal), the fracturing schedule, the fracturing-fluid composition, and the number of water-storage tanks needed for each period of time. Because of the rigorous determination of TDS in all water streams, the model is a nonconvex MINLP model that is tackled in two steps: first, an MILP model is solved on the basis of McCormick relaxations; next, the binary variables that determine the fracturing schedule are fixed, and a smaller MINLP is solved. Finally, several case studies based on Marcellus Shale Play are optimized to illustrate the effectiveness of the proposed formulation. The model identifies direct reuse as the best water-management option to improve both economic and environmental criteria.