表层导管是深水钻井作业中支撑水下井口和下部管串及水下防喷器的重要结构,研究影响表层导管承载能力的相关理论和现场实践对水下井口的稳定性至关重要。研究了作业期间各种因素对水下井口稳定性及导管承载力的影响规律。建立了适用于深水钻井的表层导管轴向承载能力理论模型及计算方法,考虑流体密度变化,提出了表层固井作业过程中水下井口轴向载荷变化的计算方法,确定了井口轴向受力最危险工况,提出了提高井口稳定性的措施。研究认为海底浅层土壤性质、表层导管承载力、喷射作业参数、固井内外流体变化引起水下井口轴向载荷变化等是导致水下井口失稳或下沉的主要影响因素。研究结果可为深水钻井表层作业提供参考。

The surface conductor is a critical structure in deepwater drilling operations, supporting the subsea wellhead, lower casing strings, and subsea blowout preventers. Researching the factors influencing the load-bearing capacity of the surface conductor, as well as the relevant theories and field practices that impact the stability of the subsea wellhead, is of paramount importance. This paper investigates the influence patterns of various factors on the stability of the subsea wellhead and the load-bearing capacity of the conductor during operations. It establishes a theoretical model and calculation method for the axial load-bearing capacity of the surface conductor applicable to deepwater drilling. By considering changes in fluid density, a calculation method for the variation of axial loads on the subsea wellhead during surface cementing operations is proposed. The most critical operating conditions for axial forces on the wellhead are identified, and measures to enhance wellhead stability are suggested. The study concludes that the properties of shallow seabed soil, the load-bearing capacity of the surface conductor, jetting operation parameters, and changes in axial loads on the subsea wellhead caused by variations in fluids inside and outside the cementing process are the primary factors leading to instability or subsidence of the subsea wellhead. The research results can provide a reference for deepwater surface drilling and completion operations.