Pipelines Risk and Integrity Management in Shared Right of Way: Case Study

Some pipeline operators evaluate risk on an individual pipeline basis even if the right of way (ROW) is shared with other pipelines. Determining a ROW strip risk condition may be complex or quite simple, according to the model adopted by the analyst. If the pipelines allocated in a shared ROW belong to different operators it is very likely that they apply different methods to evaluate a risk condition. The relative risk contribution cannot be added to estimate the risk of a ROW strip. In Mexico insurance companies request studies of collective risk in pipelines to decide whether to increase a prime or reduce coverage. This request does not have technical support or engineering guidelines to perform the analysis. In Pemex there are few documented events where a pipeline failure affects parallel pipelines, known as collateral damage. There are some methods to estimate a potential collateral damage as a function of soil damping and separation between pipelines ^(Ref.2). This scheme applies for gas pipelines and has to be complemented with an ignition scenario probabilistic analysis. In the case of hazardous liquids scenarios of leak and rupture have to be considered, including potential shed routes, product concentration sites and operator response capability. Since risk is assessed with particular and specific attributes of a pipeline the probability of failure cannot be directly added to adjacent pipelines. There are some failure mechanisms common for pipelines sharing the ROW, such as external corrosion and stress corrosion cracking (SCC), with different intensity when considering coating and corrosion protection (CP) efficiency. Internal corrosion depends on other factors such as product features so it does not necessarily repeat with the same magnitude in all pipelines. Pipeline threats can be expected to be the same in this case — with different intensity. For instance, third party activity and weather can threaten all pipelines allocated in the same ROW. These pipelines may present similar symptoms with different magnitude. Cover depth, additional protection and wall thickness play an important role in reducing third party (TP) and weather and outside forces (WOF) threats. The paper provides risk results of a ROW strip based on probability of failure values. Pipelines with biggest risk contribution were identified and integrity management alignment diagrams were obtained to correlate with risk values. A simple algorithm was developed to process risk results in terms on shared ROW buffer dimensions. The study is complemented with the results of a consequence simulation analysis for a gas pipeline