Management of Internal Corrosion Threats Can Improve Long Term Integrity of Midstream Pipelines

Abstract

Abstract Midstream pipelines moving produced fluids from shale plays are susceptible to a number of potential internal corrosion threats. Although the quality of transported commodities is governed by sales agreements between producers and pipeline operators, there are practical limitations to continually monitoring and enforcing fluid compositional parameters at exchange points. Since many midstream pipeline systems were constructed in the last five years, the integrity threat of internal corrosion has yet to have an impact on operation and maintenance costs; however, corrosion is an issue that may emerge over time. Experience from over 50 years of gathering, storage and transmission pipeline corrosion history can be applied to proactively managing internal corrosion of midstream pipelines, helping to ensure the life of the assets for decades to come. Owners and operators of new midstream pipelines have an advantage over owners of older systems when developing a corrosion management plan. First, the fact that the pipeline system is new and has been subjected to no or few asset transfers (e.g. sold to another party), has not been rerouted, repaired, or otherwise modified from the as-installed condition, and likely has up-to-date construction and inspection records, can provide a solid foundation for baseline condition assessments. Second, these up-to-date design documents, construction records, and operating data can be used in conjunction with flow models and corrosion rate estimates to identify locations along the pipeline that may be susceptible to internal corrosion threats before pipeline wall loss occurs. These locations can then be monitored to provide early indications of internal pipe wall loss and to determine the need for corrosion mitigation. A corrosion allowance in pipeline design is typically based on an estimated general corrosion rate at the assumed operating conditions, however; this allowance may not be sufficient to address localized corrosion mechanisms that often occur at a higher rate. In addition, actual operating conditions may change over time, as will the rate and type of internal corrosion mechanisms. The expectation that the pipeline system will not corrode beyond the design basis during the life of the asset can lead to catastrophic, unnecessary consequences and expose the operator to significant business risk if assurance measures are not in place. To reduce this risk, pipeline owners/operators can develop and implement proactive corrosion management plans that are scientifically sound, guided by industry standards and best practices, compliant with regulations, and maintained by corrosion professionals.