Critical Mitigation Element methodology: An approach to achieving consistent risk evaluation results ☆

Abstract This paper introduces Critical Mitigation Element (CME) Methodology, an Occidental Oil and Gas Corporation (OOG) probability analysis methodology internally developed for the purpose of achieving consistent results when conducting risk evaluations throughout the company's worldwide upstream oil and gas operations. The methodology was developed as an efficient means of utilizing the strengths of Layer of Protection Analysis, LOPA. A CME is defined as a robust barrier (mitigation element) that reduces the probability by one level on the company's risk matrix or, in some cases, reduces the consequence level. In the past, OOG relied heavily on the industry historical approach to estimate event probability which resulted in very inconsistent estimations of event probability since the accuracy was based solely on the knowledge and experience of Process Hazards Review (PHR ∗ ) team members. In order to address this issue, OOG developed its CME Methodology which is similar to a LOPA approach but much more simplified in terms of determining what credit can be taken to reduce event scenario probability. The OOG CME methodology limits the layer of protection credit to those mitigation elements provided in a list of approved CMEs. CMEs are independent layers of protection that must be highly reliable upon demand. CMEs must be supported by verifiable field and test programs that are required to ensure overall CME integrity. These supporting elements are termed Key Mitigation Elements (KMEs). By using this CME methodology, OOG has demonstrated much greater consistency across their corporate-wide risk profile. Since prioritization of risk mitigation projects is based on risk levels, consistency provides an effective basis for resource allocation. OOG's implementation of the CME methodology has resulted in significantly improved PHA ∗ accuracy and consistency and, ultimately, a more efficient and effective risk management program.