Abstract: The water depth achieved by deepwater drilling in the South China Sea has been increasing annually, and three wells have been already drilled at a depth of more than 2000 meters, and the maximum depth exceeds 2600 meters. The increasing water depth results in the prolonged tripping time for drilling tools during operations in deep water, particularly ultra-deep water, and operational safety risks are increased due to the long-time exposure of drilling tools to deep water for extended periods. To reduce the frequency of tripping in deep water and enhance the efficiency of operations in shallow formations, the paper proposes an efficient "three-in-one" drilling technology for shallow formations in deep water, which is based on the analysis of regional shallow geological and mechanical parameters and practical experience from over 40 deepwater wells drilled in the South China Sea. Through the optimization of wellbore structure design, drill string and tool optimization, jet bit design, and subsea wellhead stability analysis, the "three-in-one" efficient drilling operation mode for shallow formations in deep water has been developed. This technology allows for the completion of the whole wellbore comprising surface conductor, surface casing, and intermediate casing in a single trip through innovative designs of drilling tools and tubular structure, thus simplifying operational procedures, significantly enhancing operational efficiency, and achieving the goal of deepwater drilling. The technology was applied in 10 deepwater wells in the deepwater areas of the South China Sea, such as Baiyun, Liuhua, Liwan, and Kaiping. The application results indicate that the "three-in-one" efficient drilling technology for deepwater shallow formations can reduce tripping operations by two trips compared to conventional jetting methods, by which the drilling efficiency in deepwater shallow formations can be increased by over 50 % , and the exposure time and frequency of drilling tools in deep water is also reduced.

Key words: deepwater drilling, "three-in-one" drilling technology, wellbore structure optimization, variable diameter joint, field application

摘要： 中国南海深水钻井水深逐年增加,目前已有3口井作业水深超2 000 m,其中最大水深超过2 600 m。由于水深的增加,导致在深水、尤其是超深水的浅层钻井作业中起下钻具不仅耗时长,而且钻具长时间暴露在深水中也增加了作业安全风险。为减少在深水中的起下钻具次数,提高深水浅部地层作业效率,基于中国南海已钻超40口深水井的区域浅层地质力学参数分析和实践经验,通过井身结构优化设计、钻柱钻具优化、喷射钻头设计和水下井口稳定性分析研究,提出了深水浅部地层“三合一”高效钻井技术,建立了深水浅部地层“三合一”高效钻井作业模式,该技术通过钻井工具和管柱结构创新可以实现一趟钻完成表层导管、表层套管及技术套管井段钻井作业,简化了作业流程,大幅度提高作业效率,实现了海水深钻的目的。该技术在中国南海的白云、流花、荔湾和开平等深水海域进行了10口深水井的钻井实践。应用结果表明,深水浅层“三合一”高效钻井技术相比常规喷射方法能够减少两趟钻具起下钻作业,提高深水浅层钻井作业效率50%以上,减少了钻具在深水中的暴露时间和次数。

关键词: 深水钻井, “三合一”钻井技术, 井身结构优化, 变径接头, 现场应用