Corrosion occurs in oil and gas gathering lines containing high H2S and/or CO2. In the presence of scale and bacteria, corrosion can be aggravated. A combined corrosion inhibitor (CCI-2) was developed, which provides corrosion/scale inhibition and mitigates microbially induced corrosion (MIC). A scale inhibitor with great performance and tolerance to high calcium cation concentration was incorporated in CCI-2.

Autoclave tests were conducted using a synthetic brine of medium total dissolved solids with a gas phase of 520 kPa (75 psi) H2S, 350 kPa (50 psi) CO2, and 735 kPa(105 psi) N2. CCI-2 was found to reduce the corrosion rate by 96%. Biocide testing showed that CCI-2 could effectively kill acid producing bacteria (APB).

CCI-2 was successfully applied in the field gas lines with a high content of CO2 and H2S. The brine contained bacteria and had 12% of total dissolved solids with high scale tendency. The bacteria, residual CCI-2, iron and manganese in the field brine were periodically monitored. When the residual CCI-2 is above critical micelle concentration, CCI-2 performs very well in corrosion mitigation, scale inhibition and contribution to bacteria killing.

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