Environmentally Preferred Process for Efficient Boron and Hardness Removal for Produced Water Reuse

Abstract

Abstract Treatment and reuse of produced water has become increasingly attractive. The complicated nature of produced water, however, and its variability make it challenging to reuse. Boron (B), a common component in produced water, is a concern when reusing produced water for hydraulic fracturing fluids. Excess boron in water can interfere with the timing of crosslinking reactions in hydraulic fracturing fluids, and premature crosslinking can increase friction pressure (horse power) when the fluid is being pumped. Lowering the boron concentration in produced water, therefore, will help to prevent or reduce formation damage and increase the stability of the hydraulic fracturing fluid. This paper presents a patent-pending and environmentally preferred process for boron and hardness removal from produced water. The traditional approach to boron removal has been to add chemicals (like activated alumina (Al2O3) or cerium oxide (CeO2)) or a chemically impregnated material (activated carbon) and clay as sorbents for boron removal from produced water, but these techniques have seen limited success. In these conventional approaches, sorption efficiency was affected by solution pH, initial boron concentration and other contaminants in the water. The method presented in this paper, however, is an environmentally preferred and simple process of adding liquid sodium silicate (Na2SiO3) to produced water for boron and hardness reduction. Efficient boron removal from more than 150 mg/L to less than 30 mg/L was achieved using this process, while at the same time, total hardness (as CaCO3) was reduced by more than 80%. While the waste solids that were created do contain high levels of calcium and magnesium silicate, it is proposed that they could be used for cementing material for oil industry applications thereby reducing the environmental impact of the process. Compared with other methods such as boron-selective resin, reverse osmosis (RO) or chemical sorption, this process exhibited better performance in the efficient removal of boron and hardness from produced water.