No abstract

The disaster of Macondo of 2010 changed the rules in reliability and safety standards during drilling operations. New regulations were developed in order to improve the control level on blowout risk, and all upstream operators adopted innovative technologies capable to reduce the potential risk of uncontrolled release, either by decreasing its frequency of occurrence or the expected impacts. The objective of this paper is to present a Quantitative Risk Analysis (QRA) of well blowout and measure the beneficial contribution of intervention technologies in terms of expected reduction of spill volume and associated costs. The QRA is applied to any kind of well operation (drilling, completion, workover, light intervention) and well type. The methodology relies upon different risk analysis techniques able to quantify the residual blowout risk, as well as the mitigation provided by each technology. Through Fault Tree Analysis (FTA), a value of blowout probability is calculated for each well operation. The initial blowout condition is associated with a blowout flow rate, calculated with fluid dynamic computational models depending on well flow path and release point into the environment. The evolution of each release scenario is then studied with the use of Event Tree Analysis (ETA), where a set of events, able to reduce or stop the flow, are considered with their probability of success and occurrence time (well bridging, water coning, surface intervention through killing/capping techniques, relief well operations). The value of each intervention is estimated through Decision Tree Analysis (DTA), calculating the amount of spill volume reduction and avoided spill costs. Results of spill volume and cost reduction are calculated for a set of specific wells, considering the application of killing/capping systems as well as Eni innovative technologies. The benefit of these interventions is measured in terms of Expected Monetary Value (EMV) in relation to a potential release extinguished by a relief well, which is the decisive intervention to stop the blowout, considered as the worst case scenario. Surface interventions with killing/capping techniques are the major contributors to the reduction of blowout impacts, and all additional measures which can be adopted should act in the fastest way possible before the arrival of heavy capping stack system. The main innovative contribution of the proposed QRA methodology is the association of an expected economic value to post-blowout mitigation techniques, which takes into account all possible uncertainties related to their success and intervention time. Moreover, by evaluating an economic impact of the residual spill cost, it is possible to prioritize and increase the overall efficiency of the oil spill response plan for each operational and geographical context, and improve the control on blowout risk mitigation process.

With the goal to exhibit leadership in industry process safety, North Caspian Operating Company (NCOC), Eni, and Kinetic Pressure Control have collaborated to evaluate the feasibility and potential process safety benefits from use of the Kinetic Blowout Stopper (K-BOS®) technology in High-H2S and high-pressure drilling and completions and intervention applications from artificial islands in Kashagan field. The study focused on efforts to detect any showstoppers for the application of K-BOS, quantify the reduction in the blowout probability due to its application, and summarize the information currently available about the technology. Using the Eni proprietary e-wise™ fault tree analysis approach, a quantitative risk assessment was performed to compare the probability of a blowout in Kashagan field using conventional BOP systems to the probability of a blowout with the K-BOS added to the stack. The study also reviewed OEM provided operating procedures, a risk assessment for running the equipment, as well as a feasibility study regarding any height restrictions in the BOP stack and the position of the K-BOS in the stack. The impact of alternative equipment for risk reduction such as additional redundancy was also assessed. The application of the 13 5/8" 10M K-BOS system during reservoir drilling, completion and intervention operations significantly reduces the probability of a blowout by at least an order of magnitude. For drilling operations in the most challenging Rim portion of the reservoir, the blowout probability decreases by more than 90% and the residual value is below the blowout frequency for Producing Wells. The improved shearing/sealing capacity and reduced closure time provided by the K-BOS enable a reduced likelihood of a blowout and enhance the risk profile for the oil and gas industry.