水下井口套管悬挂器偏磨事故预防技术

为了防止半潜式钻机施工过程中水下井口套管悬挂器及其连接短节发生偏磨，破坏油气井的完整性，以海上高温高压探井M井钻井过程中?273.1 mm套管悬挂器及其连接短节发生严重偏磨事故为例，分析了作业时海况、钻井平台偏离井口的程度、隔水管挠性接头是否扭卡和套管悬挂器耐磨补心的内径等可能造成套管悬挂器偏磨的因素，结合有限元软件计算结果，提出了以精确监测钻井平台偏离井口程度和选用与套管内径一致的套管悬挂器耐磨补心为主的预防技术措施。M井填井侧钻及后续的11口井进行钻修井、弃井作业时，4台半潜式钻井平台在施工中严格采取相应的预防技术措施，套管悬挂器及连接短节未发生明显偏磨。现场应用表明，预防技术能够有效保护水下井口套挂悬挂器，保证油气井的完整性。 

Prevention Technologies in the Eccentric Wear of Subsea Wellhead Casing Hangers

In order to prevent the highly uneven, eccentric wear of the subsea wellhead casing hanger and its connecting nipple during the operation of semi-submersible rig, and to further ensure the integrity of oil and gas wells, research was conducted and a preventative technology of subsea wellhead casing hanger eccentric wear is proposed in this paper. Taking high temperature high pressure (HTHP) offshore exploration well M as an example, the ?273.1 mm casing hanger and its connecting nipple experienced severe eccentric wear and the residual casing thickness failed to meet the integrity requirements. The following factors can cause eccentric wear of casing hanger: as the sea conditions during operation, the degree of drilling rig deviating from wellhead, whether the flexible joint of riser is twisted, the inner diameter of casing hanger. All factors were studied. Then, combined with the calculation results of finite element software, this paper proposes preventive measures of accurately monitoring the deviation of rig from the wellhead to correct the eccentric wear in time, and selecting the wear bushing of casing hanger with the same inner diameter as the casing. During well filling/sidetracking of well M and the subsequent drilling, workover and abandonment in 11 wells, preventive measures were adopted during operations of the four semi-submersible rigs and the casing hangers and connecting nipples didn’t experience significant eccentric wear. Field applications showed that the prevention technologies could effectively protect the subsea wellhead hanger and ensure the integrity of oil and gas wells. Thus this study showed the potential for wide application and adoption.