Cost Effective Recovery of Low-TDS Frac Flowback Water for Re-use

Abstract

The project goal was to develop a cost-effective water recovery process to reduce the costs and environmental impact of shale gas production. This effort sought to develop both a flowback water pretreatment process and a membrane-based partial demineralization process for the treatment of the low-Total Dissolved Solids (TDS) portion of the flowback water produced during hydrofracturing operations. The TDS cutoff for consideration in this project is < 35,000 ~ 45,000 ppm, which is the typical limit for economic water recovery employing reverse osmosis (RO) type membrane desalination processes. The ultimate objective is the production of clean, reclaimed water suitable for re-use in hydrofracturing operations. The team successfully compiled data on flowback composition and other attributes across multiple shale plays, identified the likely applicability of membrane treatment processes in those shales, and expanded the proposed product portfolio to include four options suitable for various reuse or discharge applications. Pretreatment technologies were evaluated at the lab scale and down-selected based upon their efficacy in removing key contaminants. The chosen technologies were further validated by performing membrane fouling studies with treated flowback water to demonstrate the technical feasibility of flowback treatment with RO membranes. Process flow schemes were constructed for each of the four product options based on experimental performance data from actual flowback water treatment studies. For the products requiring membrane treatment, membrane system modeling software was used to create designs for enhanced water recovery beyond the typical seawater desalination benchmark. System costs based upon vendor and internal cost information for all process flow schemes were generated and are below target and in line with customer expectations. Finally, to account for temporal and geographic variability in flowback characteristics as well as local disposal costs and regulations, a parametric value assessment tool was created to assess the economic attractiveness of a given flowback recovery process relative to conventional disposal for any combination of anticipated flowback TDS and local disposal cost. It is concluded that membrane systems in combination with appropriate pretreatment technologies can provide cost-effective recovery of low-TDS flowback water for either beneficial reuse or safe surface discharge.

Exploring Geochemical Signatures in Production Water: Insights from Coal Bed Methane and Shale Gas Exploration—A Brief Review

“…Maximum permissible total suspended solid concentrations in produced water ranges from 1000 mg/L [131] to 10,000 mg/L [132]. The high total dissolved solid abundance (up to 200,000 mg/L) prefers the thermal desalination process [133]. The economic operation of thermal desalination units occurs between the 20,000 and 100,000 mg/L range of the total dissolved solids [123].…”

National Alliance for Water Innovation (NAWI) Resource Extraction Sector Technology Roadmap 2021

“…will be necessary to provide cost-effective, energy-efficient desalination of resource extraction wastewaters and brines. 174,175,176,177 Most methods of treatment and desalination of produced and mining wastewaters generate residual streams. Management of these residual streams is complicated by the quality, quantity, and potentially hazardous nature of concentrated brine streams.…”

Water Treatment: Are Membranes the Panacea?

“…Ion exchange and NF membrane softening are also viable options for hardness reduction, depending on source water quality, system size, and water quality objectives. Both TDS and hardness can be removed via RO, but starting TDS levels greater than ∼35,000 mg/L present economic challenges (110). Thermal processes, including MD, are promising for high-TDS PW, as MD is not significantly influenced by feed salinity (111).…”