2018034 PRODUCED WATER RECLAMATION IN THE PERMIAN BASIN USING CHLORINE DIOXIDE

High disposal costs and a limited availability of freshwater have led many industry players in the Permian Basin to reclaim produced water and use it in subsequent well fracturing. This reclamation process typically involves pumping produced water from numerous production batteries to a central location where it is placed in storage in large surface impoundments until such time that it is needed in fracturing operations.  Unfortunately, a natural process referred to in the oil and gas industry as “souring” can occur within these impoundments during the time period when the produced water is being stored.  Souring can occur quickly and render produced water completely unsuitable for subsequent use in fracturing without extensive and costly in situ chemical and/or physical treatment, thereby negating all incentives the industry has for recycling this water. Produced water also typically contains a high concentration of dissolved ferrous iron (Fe2+), which has the potential to cause significant operational issues downhole if used in fracturing without some form of pretreatment.

This paper describes in detail how constituents present in produced water cause surface impoundment souring to occur, and demonstrates, with supporting field application data, how chlorine dioxide (ClO2) can facilitate economical reclamation by simultaneously treating both problematic aspects of produced water prior to its subsequent storage in surface impoundments. First, ClO2 readily oxidizes undesirable soluble ferrous iron present in produced water to the insoluble ferric form (Fe3+).  Second, ClO2 helps break the natural “chain of causation” that leads to impoundment souring by destroying bacterial emulsions, which in turn allows entrained oil to effectively separate from the water, and suspended solids, including precipitated ferric iron, to drop out via gravitational settling and/or mechanical filtration. Finally, because ClO2 is a highly penetrating gas, it quickly pervades any volume of produced water requiring treatment, thereby allowing for process adaptation to virtually unlimited flowrates.