This paper reviews steps taken to mitigate coiled tubing string failures resulting from microbial-induced corrosion (MIC) in the Eagle Ford by initiating an effective water treatment process alongside the use of coiled tubing with bias weld in sour fatigue similar to base tube performance.
Premature failures of coiled tubing strings can be capital intensive for most coiled tubing companies in the current oil and gas market. In 2015 there was a total of three string failures resulting from MIC in the Eagle Ford—with an estimated cost of USD 750,000. MIC has been implicated in few corrosion related challenges in the well service industry in the past.
The water treatment process was implemented in field on 21 December 2015. The mitigation process involved treating the circulating fluid in the fracturing tanks on location with chlorine dioxide, peracetic acid, or BDNP quick killer biocides. These are combined with glutaraldehyde or combination solution of glutaraldehyde and quaternary ammonium (glut/quat combo) for longer term bacterial control at the start of each job. Water samples of the circulating fluids are taken within 8 hours to get the relative light units (RLU), which determined the proper time to re-treat the water on location. RLU values were also correlated to typical sulfur reducing bacteria (SRB) and acid producing bacteria (APB) levels in South Texas. The water treatment process has been administered, along with the continuous metering of the bacteria and introduction the new coiled tubing technology, for 12 months with no string failure has been encountered. Further analysis of the effectiveness of the treatment will be conducted later in the string life when the involved strings are retired.