Towards sustainable oil/gas fracking by reusing its process water: A review on fundamentals, challenges, and opportunities

Due to the constraint of fresh water, the reuse of flowback and produced water (FPW) with high TDS, is critical to minimize the environmental impact of oil/gas exploration. The underlying challenge is the negative effect of salts present in FPW on the chemistry of fracking. The solution is to develop excellent fracking chemistry with salt- and temperature-resistant. Herein, we have comprehensively discussed FPW characteristics, and the technical challenges of reusing FPW; we then focus on the design strategy of developing fracturing fluids that are effective under harsh conditions. The environmental benefits and economic implications of using FPW in fracking are highlighted. In summary, we proposed that a new type of fracturing fluid should be developed in future, which contains a new functional gelling agent prepared by grafting the synthetic polymer on the biopolymer, bio-based nano-crosslinkers, cost-effective nano-breakers, and FRs with high elasticity and salt-resistance, which will have great potential for the reuse of FPW and the development of unconventional formations. We envision that this review will provide insights to stimulate new thinking and innovation in oil/gas fracking that is not only green/sustainable, but also economic/practical, while meeting the demand for high performance under harsh environments with high salt and high temperature.