Abstract
Oil and gas production pipelines are susceptible to internal corrosion at locations where flow conditions promote water accumulation and solid particles settlement (precipitation). These deposits form diffusion barrier between the produced fluids and underlying substrate, which results in water chemistry near the steel surface different from that in the bulk fluids. This can potentially lead to an accelerated localized corrosion through under deposit corrosion (UDC). Successful corrosion management of UDC is based on risk assessment, mitigation and monitoring. As a normal practice, mechanical scraping along with chemical treatment is commonly applied as the mitigation for UDC. However, for this case, installing a scraper facility was not economically viable for new pipelines connected to an ageing platform that was meant for temporary period. Therefore, an assessment was conducted to determine if solids deposition and associated corrosion risks could be completely eliminated or tolerated to an acceptable level for safe continuous operation before diverting the pipelines permanently and equipped with scraping facility. The assessment utilized a novel approach consisting of advanced precipitation modelling, UDC laboratory testing including solids characterization in addition to flow assurance and corrosion simulation. The results showed that the overall deposition and associated corrosion risk is low. By implementing the recommended measures, these pipelines can be operated safely without scraping facilities temporarily, after which the pipelines will be routed to future scraping facility
