自升式钻井平台穿刺分析

 自升式钻井平台是近海石油和边际油田开发的重要设备。据统计，穿刺事故占自升式钻井平台总事故的比例超过了50%，造成平台严重损坏和人员伤亡。以Arab drill 19自升式钻井平台和中国某自升式钻井平台的穿刺事故为例，分析穿刺事故发生的原因，说明穿刺事故的危害。采用投影面积法，分析了中国某自升式钻井平台在渤海某井位发生穿刺事故的可能性，结果表明，该平台存在较大的穿刺风险，并预测了穿刺后的插桩深度。对比平台实际插桩深度，预测结果存在较大误差。结合穿刺研究的最新成果，分析两者存在误差的原因：实际插桩过程中，桩靴底部将形成砂土塞，该砂土塞会极大地提高土体的极限承载能力，导致实际插桩深度比预测插桩深度浅。

Investigation of the Punch-through in Jack-up Rigs

Jack-up rigs are widely used in offshore oil and marginal oil field development. According to statistics, punch-through accidents account for more than 50% of jack-up rigs' accidents, leading often to serious damages of the jack-up rigs and casualties. Taking the Arab drill 19 jack-up and a Chinese jack-up as examples, the causes of the accidents and the seriousness of consequences are analyzed. The projected area method is used to study the possibility of punch-through for a domestic jack-up at a well site in Bohai Bay. It is found that the punch-through risk at the well site is high. The calculated penetration depth does not agree very well with the actual operational record, with a great error, which is analyzed in this paper based on new research results of punch-through. It is shown that during punch-through in a jack-up rig, a sand plug will be formed under the spudcan of the jack-up rig, which increases the ultimate bearing capacity of soil, and reduces the actual depth.