深水钻井隔水管与防喷器紧急脱离后的反冲响应分析

Recoil Analysis for Deepwater Drilling Riser after Emergency Disconnection with Blowout Preventer

深水钻井中,若底部隔水管总成与防喷器紧急脱离,隔水管会反冲,易导致钻井事故。为了解隔水管紧急脱离后的反冲响应规律,分析了隔水管反冲产生的原因及反冲响应过程,明确了隔水管反冲响应的机理和关键影响因素。在此基础上,建立了隔水管张紧器及钻井液下泄分析模型,以探究张紧力随活塞冲程变化的规律及钻井液下泄时作用在隔水管上的摩擦力随时间变化的规律。综合考虑各关键影响因素,基于ANSYS有限元分析软件,建立了隔水管反冲响应分析模型,并以1 500m水深钻井中的隔水管为例,计算、分析了不同紧急脱离时刻和顶部张紧力条件下的反冲响应。分析结果表明,与防喷器紧急脱离后,隔水管在顶部张紧力作用下加速向上反冲,伸缩节冲程减小。研究认为,紧急脱离的时间与顶部张紧力的大小对隔水管反冲响应有重要影响,因此应合理选择紧急脱离时刻和顶部张紧力,以保证紧急脱离条件下深水钻井隔水管系统的作业安全。

During deepwater drilling process,recoil behavior of drilling riser will occur once the lower marine riser package is quickly disconnected from the blowout preventer,which could lead to serious drill- ing accidents. In order to understand riser recoil behavior, the reason for riser recoil and the recoil process were analylzed,and the main factors that influence riser recoil response were determined. Based on these studies, the analysis model of the tensioner system was built to investigate the relationship between tension force and piston stroke. Drilling fluid flow model was built to work out the relationship between friction force imparted by drilling fluid on riser and time. Finally, the modeling method for main influence factors in finite element software was studied, and the recoil analysis model was built in ANSYS software. Taking the riser in 1 500 m deep water drilling as an example,riser recoil response at different points of disconnection and top tension forces were calculated and analyzed. The results showed that the riser recoiled upward quickly after being disconnected from blowout preventer under the effect of top tension, resulting in signifi- cant shortening of telescopic joint stroke. The riser recoil response was heavily dependent on the point of disconnection and top tension force. Proper timing of disconnection and top tension force could result in a sensible riser recoil response,ensuring operation safety of deepwater drilling riser.