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Abstract

Gas cutting typically occurs in deepwater drilling of highpressure gas reservoirs. If gas cutting is not detected in a timely manner or if the designed well control capacity is insufficient, blowout and other accidents may occur. To address this problem, this paper presents a gas-liquid flow model and kill model in deepwater drilling for the simulation analysis of the gas cutting and killing processes in deepwater drilling. By calculating the maximum allowable killing casing pressure, well control risks under various overflow rates, formation pressures, and kill rates were analyzed, and a well control capacity-based risk analysis method for gas cutting in deepwater drilling was established. In this method, the well control capacity under various drilling conditions was considered. Moreover, by using this method, the well control risk after a gas cut under various conditions can be analyzed to obtain the safe construction parameter range and overflow monitoring index. An example is presented to demonstrate that the established method can be used to recommend safe overflow range, maximum allowable formation pressure prediction error in the current condition, and safety kill rate range under specific working conditions. Thus, the proposed method has practical application in dynamic risk assessment of gas cutting in deepwater drilling.

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