Well Integrity Management - Application of Risk Assessment to Optimize Your Decisions

Abstract

Quantitative Risk Analysis (QRA) has been used to identify and manage risks in the Oil & Gas industry for decades. However, the important steps of well construction and well intervention operations have typically only been addressed using generic data, if even quantified at all. This data, which primarily is based on North Sea experience, may not be relevant for the specific well operations being evaluated. Further, using generic data does not provide a basis to identify relevant risks and support in identifying and implementing effective risk reducing measures. Quantitative Risk Assessments are used to improve safety while at the same time manage and assure cost effective risk mitigating measures are implemented. By identifying the key risk drivers and main contributors to the risk exposure, the QRA provides a tool to prioritize and focus on the most cost effective risk reducing solutions. Further, when different risk reducing, or risk mitigating, measures are proposed, the QRA is an effective tool to compare and evaluate the effect of these different risk reducing measures and help select optimal solutions. These evaluations are however only possible if the QRA model is relevant and includes information and relevant assumptions related to the specific well operation. Thus, only when the QRA incorporates information about the specific drilling or well operation being evaluated, can it be used to evaluate if: The drilling and well control equipment is adequate.The operating procedures are appropriate and address the relevant risks.That the crew and personnel have the required competence and experience. By incorporating the relevant and specific information related to the drilling or well operation being evaluated, the QRA can provide a powerful tool to prioritize and evaluate effective risk reducing or risk preventive measures, and systematically be used to manage well control and well integrity challenge related to the well and well operations. In this paper, a systematic approach and methodology to perform QRAs for well construction and well intervention operations is presented. Similar to traditional topside process QRAs, which evaluate the process layout (P&IDs), safety and shutdown systems, the well QRA addresses the specific well operations. The methodology considers and evaluates the actual well and subsurface conditions, the drilling rig, drilling and well control equipment, in addition to the procedures and the competence of the drilling crew involved in the operation. The methodology is demonstrated through a few case examples taken from specific well QRA studies.

Risk analysis and Assessment of Wellbore Integrity Failure in Underground Gas Storage Based on Bayesian Network

“…Where, Li is the risk value of the risk factor i; pi is the probability of occurrence of the risk factor; Ci is the severity of the risk factor. The severity of wellbore integrity risk barrier unit failure is divided into 5 levels [9] . The specific classification results of risk severity levels are shown below.…”

“…Table 2. Severity levels for different events [9] Number The wellbore integrity failure risk degree R [10] can be calculated according to equation :…”