Employing Effective Water Treatment in West Texas to Mitigate Surface Equipment Failures

Abstract

Effective bacterial control is a key component of a successful fracturing stimulation. Currently water sources can have extremely high levels of aerobic and anaerobic bacteria that can lead to chemical degradation, microbial induced corrosion (MIC) and souring of wells due hydrogen sulfide generation. Oxidative biocides are widely used per rapid kinetics of disinfection with the capability to provide good control of bacteria loadings with short residual lifetimes. This paper reviews steps taken to mitigate failure in fluid cylinders and flow iron surfaces that come in contact with the fluids, causing them to degrade much quicker than the normal expected life when used oxidative biocides. Premature failures of fluid ends and iron missiles are capital intensive for most hydraulic fracturing companies in the current oil and gas market. In the duration of 2 months in summer 2016, there was an unsustainable increase in maintenance costs by an estimated USD 4 million for two fracturing fleets. MIC and overtreatment of water with chlorine dioxide have been implicated in this premature failure of iron surfaces. The water treatment process was implemented in the field in summer 2016. The mitigation process involves pretreating produced water with chlorine dioxide with no residual, which is then complemented with conventional biocides and combos for longer term bacterial control at the start of each job. Water samples of the circulating fluids are taken every 2 hours to get the relative light unit (RLU), which determines the proper timeframe for retreating the water on location. RLU values were also correlated to typical sulfur-reducing bacteria (SRB) and acid-producing bacteria (APB) levels in West Texas. The water treatment process, with continuous monitoring, implemented over a 3-month period dramatically increased the life of stainless steel fluid ends and missiles from the 300 pumping hours and 5 months respectively. Further analysis of the effectiveness of the treatment is conducted later when the equipment is retired.