Zero or Negatively Valued Waste Produced Water to Positively Valued Feedstock by Recovery of Valuable Minerals and Fresh Water

Abstract

The oil and gas industry consumes substantial volumes of fresh water and salts for various oilfield applications. At the same time, large volumes of various high-salinity brine streams are produced during the production of oil and gas. These produced water streams, not being utilized for any other applications such as reservoir reinjection for pressure maintenance, are becoming an increasing burden for the environment. From a societal and governance perspective, an economical Zero Liquid Discharge (ZLD) process coupled with mineral recovery is the most sustainable path to follow. Several existing water treatment technologies can be considered to obtain produced water ZLD. However, to meet the economic and environmental targets, a careful selection of technologies is adapted to achieve full recovery of water and minerals from a given produced water stream. A low temperature evaporation and crystallization dynamic vapor recovery is used for high salinity (up to 200,000 ppm TDS) produced water. The rejected brine from these processes is further treated to separate valuable minerals selectively. For the high salinity produced water, dynamic vapor recovery technology is proven to have a recovery efficiency of greater than 75%, generating less than 200 ppm TDS water for industrial and agricultural use. The reject stream (saturated salt solution) from this process is subjected to mineral recovery, resulting in the recovery of 99.3% pure NaCl as one of the first recovered salts. Several existing separation technologies are evaluated to recover additional valuable minerals (Calcium, Strontium, Magnesium, and Lithium products) from the reject stream of the NaCl recovery process. Lessons learned from other industrial brine treatment projects dealing with complex brines are carried over to the Oil and Gas applications to introduce the effective, reliable, and economical treatment of brines such as produced water. The revenue from the treated water and minerals can be more to offset the capital and operating costs. Thus, "any non-utilized Produced Water could be priced as positively valued feedstock instead of a zero or negatively valued waste product."