Cost-efficient and Improved Treatment Technology for Produced Water Reuse

Abstract

Abstract Produced water reuse for hydraulic fracturing fluids is becoming more attractive for oil and gas completions, especially in areas with limited access to fresh water. However, components in produced water such as suspended solids, bacteria, and certain ions (boron, iron, etc.) may reduce fluid stability or cause formation damage. This paper presents a cost-efficient and innovative system for produced water treatment and reuse along with a comparison with traditional technologies. The presence of iron and boron is common in produced water. Iron may cause formation damage by forming iron sulfide scale and interfere with proper gel formation in cross-linked fracturing fluids. Excess amounts of boron can interfere with crosslinking reactions in fracturing fluids, causing them to crosslink prematurely or excessively. The constant fluctuation of these components makes it challenging to apply a single technology or traditional technology for efficient treatment. The new system presented in this paper has a unique design and combines several technologies to overcome these limitations. Traditional methods for iron removal, such as oxidation or pH increase, can be compromised by the high level of hardness in produced water. Accurate real-time analysis is required to adjust the dosage of the chemicals applied, resulting in extra costs. Traditional chemical methods for boron removal need large volumes of chemicals and generate considerable amounts of waste. Conventional boron-selective resins have shown high efficiency for reducing boron concentration, but the hydrocarbons and suspended solids in produced water limited this method's efficiency. With the new innovated process, lab scale testing and a field trial have demonstrated efficient boron removal from over 120 mg/L to below 5 mg/L, allowing a conventional delayed cross-linked hydraulic fracturing fluid to be successfully prepared using 100% treated produced water. In addition, this technology has been demonstrated to be faster and more efficient in iron reduction than traditional methods. Iron removal from a level greater than 900 mg/L to less than 5 mg/L from high-concentration oil contained water was achieved with less than 5 minutes of contact time. This new process exhibited significant bacteria control capabilities as well, reducing the risk of bacteria-caused formation damages that can result in a loss of well productivity, corrosion, or HSE issues. Compared with traditional technologies, this new method has exhibited cost-efficient remediation of produced water, especially in the removal of iron, boron, suspended solids and bacteria, using minimal amounts of chemicals and generating a relatively small waste stream.