Assessing Well Integrity Risk: A Qualitative Model

Abstract

For successful delivery of Well Integrity, there needs to be an understanding of the risks that can cause undesirable events such as safety hazards or loss of containment. Performing a risk assessment on a well, or type of well, will help determine and rank the potential risks and provide information that allows limited resources to be applied in the most effective manner. The main objectives of performing a risk assessment include: Follow a formal process to assess risk consistently and to enable comparison between well barrier failure mode scenarios;Qualitatively assess well barrier failure risk for every segment of a well;Document suggestions that are offered by the risk assessment team for mitigating well barrier failure risk; andProvide a report of the methodology, failure mode scenarios, risk ranking, and potential mitigation actions for use as a reference tool for managing well integrity on a routine basis. The Well Integrity Risk Assessment Model follows a common qualitative risk assessment process; a team-based, structured brainstorming format, utilizing the What-If Methodology, to identify potential hazards associated with well barrier failure modes. In addition, the model has the following attributes: Incorporates a unique method to segment well barriers into discrete sections, successively "failing" each section for evaluation. The list of analyzed well barrier failure modes, along with their risk ranking, becomes the risk register for the well or type of well.Is adaptable for assessing well barrier failure modes on a single well, or a group of wells, having the same general design parameters. An entire well portfolio can be assessed quickly by analyzing types of wells rather than individual wells.Can be used to assess well barrier failure risk for any type of well.The model can easily be modified to conform to any company's risk model. The Well Integrity Risk Assessment Model has been proven to: Successfully assess well barrier failure risk for thousands of wells;Focus specifically on well barrier failure modes, and as a result is an effective tool that should be incorporated into a "Best in Class" Well Integrity Program;Be utilized as a management tool to provide guidance for how limited resources can be used effectively to continuously deliver well integrity.

How to Design Rating Schemes of Risk Matrices: A Sequential Updating Approach

“…Risk matrices are easy to implement and can be implemented even where data are limited. Therefore, they have become popular decision‐support tools in both the public and private sectors, in areas such as well‐integrity risk, drilling hazard management, climatic change responses, and so on. However, despite its simplicity and wide usage, recent research has revealed several flaws in the risk matrix.…”

“…The answers to the first question (a) depend on the goals of using the risk matrix. If one employs risk matrices to assist in determining the acceptance of a risk, perhaps three risk ratings are sufficient, such as “broadly acceptable,” “as low as reasonably practicable,” and “unacceptable.” However, when risk matrices are used to prioritize several risks, risk matrices should have a higher resolution to better differentiate all the risks . As a result, when we design the rating scheme of a risk matrix, the method we use should work as well as possible regardless of the various inclinations for resolution.…”