深水钻井阶段水下井口稳定性及其影响因素分析

Analysis of wellhead stability and influence factors in deepwater drilling stage

深水钻井阶段,水下井口在BOP和套管作业所产生的竖向载荷以及隔水管所受风浪流等环境横向载荷的作用下存在失稳风险。分析了深水钻井隔水管及BOP安装前后水下井口受力情况,建立深水井口稳定性分析模型;结合某深水井钻井实例,对深水钻井阶段水下井口进行力学计算,并对水下井口稳定性的影响因素进行了敏感性分析。算例分析表明:深水钻井阶段,水下井口受到的竖向承载力对其影响较小,横向载荷对其影响较大;顶张力与水下井口偏移和倾角呈正相关,弯矩受顶张力影响不明显;导管出泥高度对水下井口的稳定性影响较大;钻井液密度变化对水下井口弯矩几乎没有影响。

In the stage of deepwater drilling,there is a risk of subsea wellhead instability under the combined action of the vertical loads of BOP and the lateral loads of wind,wave and flow on the riser.This paper analyzes the subsea wellhead forces before and after the installation of riser and BOP,establishes a bearing capacity analytical model of the wellhead for deepwater drilling.Then,combined with an actual case of deepwater well drilling in China,it carries out the force calculation of the subsea wellhead in drilling stage and the sensitivity analysis of the influence factors affecting the stability of deepwater wellhead.The results indicate that in drilling stage,the vertical bearing capacity has no obvious influence on the subsea wellhead,and the lateral load has obvious influence on the subsea wellhead.The top tension is positively correlated with the deflection and inclination of the subsea wellhead,the bending moment is not obviously affected by the top tension,the conduct height above soil has a great influence on the stability of the subsea wellhead,and the variation of drilling fluid density has little effect on the bending moment of the subsea wellhead.