A Well-Specific Approach to the Quantification of Well Control

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 124024, ’KickRisk - A Well-Specific Approach to the Quantification of Well-Control Risks,’ by O. Arild, SPE, E.P. Ford, SPE, T. Loberg, SPE, and J.W.T. Baringbing, SPE, IRIS, originally prepared for the 2009 SPE Asia Pacific Oil and Gas Conference and Exhibition, Jakarta, 4-6 August. The paper has not been peer reviewed. Drilling wells in which there is a small pressure margin often is challenging with respect to well-control issues. A kick, which occurs if the wellbore pressure drops below the pore pressure, is one of the major risks being dealt with in the planning phase of the well. A kick can occur as a result of several factors. Because the ultimate consequence of a kick may be a blowout, it is essential to be able to assess and reduce the probability of a kick occurring. Introduction The oil and gas industry is taking on increasingly challenging drilling operations; drilling in severely depleted mature reservoirs, high-pressure/high-temperature drilling, deepwater drilling, and ultradeep wells are some examples. In any drilling operation, proper well control is essential. Loss of well control may lead to a blowout, which represents one of the most severe threats associated with exploration and exploitation of petroleum resources, involving the risk of human lives and environmental and economic consequences. The more challenging the operation, the more effort should be spent in the planning phase on assessing the risks related to loss of well control. When analyzing new and unproven drilling technology, or drilling in challenging environments, statistical data or experience rarely are available. Thus, to assess risks related to such operations, a well-specific approach often is the only option. A well-specific approach can be undertaken by using a probabilistic risk-assessment (PRA) approach, which provides a body of practical techniques that can help engineers and risk managers predict and manage risks. The kick risk-evaluation model (REM) uses this approach. Proper well control typically is ensured by using two independent barriers. The primary barrier is the mud or fluid column, and the secondary barrier is the blowout preventer (BOP). The REM addresses the potential loss of both these barriers; however, the full-length paper addresses only the loss of the primary barrier (i.e., a kick occurring). Avoiding the occurrence of kicks is important because blowout probability is proportional to the kick probability; efforts made to reduce kick probability directly reduce blowout probability. The objectives of the full-length paper are to provide the reader with an appreciation of probabilistic risk analysis, insight into the REM, and an understanding of the practical application of the REM tool.