51316-7815-Understanding the role of microbes in frequent coiled tubing failures

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Product Number: 51316-7815-SG

ISBN: 7815 2016 CP

Author: Mohita Sharma

Publication Date: 2016

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Understanding the role of microbes in frequent coiled tubing failureMohita Sharma1 Dongshan An1 Kristen Baxter2 Matthew Henderson2 Lem Edillon3 Gerrit Voordouw11Petroleum Microbiology Research Group Dept. of Biological Sciences University of Calgary 2500 University Dr. NW Calgary AB Canada T2N 1N42Fusion Technologies Inc. 3750-46 Ave. SE Calgary AB Canada T2B 0L13Step Energy Services 300 505 - 3rd Street SW Calgary AB T2P 3E6The use of coiled tubing has strongly increased in the oil and gas industry in recent years. Potential corrosion problems arise from re-use of low quality water in closed loop coiled tubing operations. These problems frequently result in failures. Water chemistry corrosion rates using the weight loss method microbial counts and microbial community compositions were monitored for 5 samples from a site in field A and for 15 samples from a site in field B. The samples from field A represented a failure. At both sites source water injected for fracturing was produced stored and then re-injected. Four samples of recycled produced waters retrieved from field A had high salt (1.13M) and ammonium (24-54 mM). Source water A had a lower salt concentration (0.58 M); this was the only sample that had significant acid-producing bacteria (APB 2.4x106/ml) and sulfate-reducing bacteria (SRB 9.4x106/ml). Such high numbers were not found in recycled produced waters A which had 0 to 102 APB/ml and 0 SRB/ml. All these samples had general corrosion rates of 0.1 mm/yr as determined by weight loss. Recycled produced waters B showed a gradual increase in salt (from 0 to 0.46 M) and ammonium (from 0 to 7.7 mM) concentrations with increased cyles of reuse. Source water B had 2.4x103 APB/ml; 0 APB/ml following biocide treatment. Nevertheless recycled produced waters had high numbers of APB (up to 107/ml) indicating growth. None of these samples had SRB. The general corrosion rates of samples collected from field B for incubations initiated in the lab ranged from 0.09 to 1.31 mm/yr (average 0.25 mm/yr). The high rate was for a recycled water taken from a tank prior to re-injection. Interestingly general corrosion rates for this same recycled produced water for incubations initiated on site were also very high (0.89 0.84 and 0.99 mm/yr) relative to those from an other site (0.12 and 0.08 0.08 0.08 mm/yr). The reasons for these high rates are currently under investigation. DNA sequencing may indicate whether specific microbes contribute.