深水油气井表层导管下入深度计算方法

深水表层导管是深水油气钻井与生产的重要通道,是水下井口装置的主要持力结构,表层导管下入深度直接影响到水下井口的稳定性以及海上作业安全。基于表层导管基本功能和主要安装方法,针对不同海底的土力学特性,开展了钻入法和喷射法安装表层导管适应性及选择方法研究。基于油气井表层导管垂向受力分析,揭示了表层导管及上部井口载荷与表层导管外表面摩擦力之间关系,建立了钻入法和喷射法表层导管合理下入深度模型。从油气井表层导管横向受力分析出发,揭示了井口载荷、表层导管尺寸、表层导管钢级壁厚、表层导管出泥高度对水下井口稳定性影响规律,建立了水下井口出泥高度设计方法和计算模型。表层导管下入深度计算方法已在中国南海水深300~2 619 m的几十口深水井得到成功应用,该研究成果支撑了这些油气田的钻完井安全高效作业和后期油气生产安全运行。

Calculation method of surface conductor setting depth in deepwater oil and gas wells

The surface conductor is an important channel for oil and gas drilling and production in deep water. It is the main holding structure of underwater wellhead equipment. The setting depth of surface conductor plays an important role in the stability of underwater wellhead and the safety of offshore operations. Based on the basic functions and the main installation methods of surface conductor, according to the different submarine soil mechanical properties, a study has been carried out on the applicability of the drilling method and jetting method used to install surface conductor. Based on analyzing the vertical force of surface conductor in oil and gas wells, this study reveals the relation between the surface conductor, the upper-wellhead loading and the friction on the outer surface of surface conductor, and then establishes a reasonable setting depth model for surface conductor under the drilling method and jetting method. Based on analyzing the lateral force of surface conductor in oil and gas wells, this study discovers the influences of submarine current loading, the size, steel grade, wall thickness and sludge height of surface conductor, on the stability of underwater wellhead, and then sets up the design method and calculation model for the sludge height of underwater wellhead. The calculation method of surface conductor setting depth proposed herein has been successfully applied in dozens of deepwater wells below 300-2 619 m in the South China Sea. The research results support the high-efficient drilling and completion of wells, and guarantee the safe operation during oil and gas production.