(347f) A Recycle/Reuse Network for the Optimal Water Management in Hydraulic Fracturing Operations

Recently, there have been substantial discoveries of shale gas reserves in North America. Hydraulic fracturing technologies have facilitated the production of shale gas trapped in tight formations. According to the Energy Information Administration (EIA), by the year 2035 shale gas is expected to provide about half of the total natural gas supply in the U.S. The EIA also estimates that the U.S. has enough natural and shale gas to meet domestic electricity demands for 575 years at current electricity generation levels. Certainly, this information highlights the importance and the enormous potential of shale gas in the future. However, this industry deals with several challenges, where the most important concern is related to the water owing to huge amounts of water demanded by hydraulic fracturing phase to be successfully implemented and once the completion phase has finished a portion of the injected water during the fracking returns to the surface and according to the time (and even the quality water is different) it can be classified in flowback, transition and produced water. Then, a key process consists in treat and storage these streams with the purpose to recycle or reuse them and reduce the fresh water consumption. This aspect is essential for regions with a strong water scarcity. In developing a water recycle/reuse strategy, it is important to consider the segregation and avoid the mixing of flowback, transition and produced water to be treated and storaged. The recycled water is able to be sold and used in other activities.

Thus, this work proposes a formal optimization formulation for the recycle/reuse network implemented in shale gas operations considering the economic target, which is composed by the costs of fresh water, treatment, storage, disposals (including operating and capital costs) and transportation as well as the sale of the recycled water. The environmental objective aims to minimize the fresh water requirements. The methodology considers a fixed scheduling for the completion operations in order to implement the approach. Finally, an example problem is presented to show the applicability of the proposed methodology