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Scheduling for the completion phase in each well.
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This work presents a mathematical programing formulation for the optimal management of flowback water in shale gas wells considering economic and safety aspects. The proposed formulation accounts for the time-based generation of the flowback water, as well as the options for treatment, storage, reuse, and disposal. The economic objective function i...
Context in source publication
Context 1
... the flowrate required in each well during the completion time is 428.57 m 3 /d; while the flowback water obtained after this phase has Figure 3. In this figure, the hydraulic fracturing crew 1 completes the wells 1-8, hydraulic fracturing crew 2 works the wells 9-15 and finally crew 3 operates the wells 16-20. ...
Citations
To manage wastewater produced by hydraulic fracturing operations in the production of shale gas, this chapter presents a mathematical programming approach for strategic planning. The goal of the presented approach is to choose the best course of action for treatment, storage, and reuse. Along with the long-term produced water, the technique also considers the unpredictability of wastewater properties, such as the short-term flowback and transition water. Wastewater segregation is taken into consideration as a potential solution due to the variations in the pollutant contents found in the different kinds of wastewater. Moreover, seasonal variations in freshwater supply are taken into consideration by the model. Environmental and economic objectives are considered. Finding the lowest possible overall cost—which includes freshwater, treatment, storage, and transportation expenses—is the goal of the economic objective function. Water that is reused is rewarded. The primary goal of the environmental objective is to decrease the amount of freshwater required for the hydraulic fracturing process. The presented model establishes trade-offs between costs and water usage. Results from a case study demonstrated that up to 32.43% less freshwater can be used and up to 12.26% of the total wastewater from wells can be recycled for hydraulic fracturing requirements.
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.
One of the critical problems in cooperative shale gas supply chains and production systems design is life cycle optimization of the economic and environmental performance under uncertainty. This study develops an inexact multi-criteria decision making (IMCDM) model with consideration of shale gas production profiles and recoverable reserves. The IMCDM framework is based on an integration of life cycle analysis, interval linear programming, multi-objective programming, and multi-criteria decision analysis approaches. An application to the Marcellus Shale supply chains is presented to demonstrate capabilities and effectiveness of the developed model, where the future spread in shale gas output follows from the variation in drilled well counts according to different scenarios. Design and operational decisions with respect to well drilling schedule, shale gas production, freshwater supply, wastewater disposal, and greenhouse gas (GHG) emissions are then generated. An optimal strategy is further provided for stakeholders after evaluation of the trade-off among multiple criteria.
This study develops a multi-level programming model from a life cycle perspective for performing shale-gas supply chain system. A set of leader-follower-interactive objectives with emphases of environmental, economic and energy concerns are incorporated into the synergistic optimization process, named MGU-MEM-MWL model. The upper-level model quantitatively investigates the life-cycle greenhouse gas (GHG) emissions as controlled by the environmental sector. The middle-level one focuses exclusively on system benefits as determined by the energy sector. The lower-level one aims to recycle water to minimize the life-cycle water supply as required by the enterprises. The capabilities and effectiveness of the developed model are illustrated through real-world case studies of the Barnett, Marcellus, Fayetteville, and Haynesville Shales in the US. An improved multi-level interactive solution algorithm based on satisfactory degree is then presented to improve computational efficiency. Results indicate that: (a) the end-use phase (i.e., gas utilization for electricity generation) would not only dominate the life-cycle GHG emissions, but also account for 76.1% of the life-cycle system profits; (b) operations associated with well hydraulic fracturing would be the largest contributor to the life-cycle freshwater consumption when gas use is not considered, and a majority of freshwater withdrawal would be supplied by surface water; (c) nearly 95% of flowback water would be recycled for hydraulic fracturing activities and only about 5% of flowback water would be treated via CWT facilities in the Marcellus, while most of the wastewater generated from the drilling, fracturing and production operations would be treated via underground injection control wells in the other shale plays. Moreover, the performance of the MGU-MEM-MWL model is enhanced by comparing with the three bi-level programs and the multi-objective approach. Results demonstrate that the MGU-MEM-MWL decisions would provide much comprehensive and systematic policies when considering the hierarchical structure within the shale-gas system.
