摘要
深水地层由于上覆海水密度低导致其压实程度低,破裂压力与坍塌压力之间的压力窗口窄,相应的钻井液安全密度窗口窄,这使得溢流和井漏频繁发生,如果处理不当易引发井喷事故。应用屏障与操作风险分析法,以事故发生实际概率相对于平均概率的增幅来描述风险高低,建立深水窄压力窗口钻井井控风险定量评价模型。以深水井涌为初始事件,在考虑呼吸效应的基础上,建立深水窄压力窗口钻井井涌事件树。初始事件井涌发生后,经过8项事件工序,最终可能产生22种结果,其中有7种结果为井喷及井喷失控的情况。根据建立的事件树设置7个预防性屏障,用以阻止井涌发展到井喷,并通过敏感性分析得出各屏障失效对整个屏障系统影响大小。根据国外文献计算出深水钻井井喷发生的行业平均概率为1.209×10^(-5),以一口已钻深水井为例,进行了风险定量计算,计算结果与该井实际情况一致,验证了模型的可靠性。
The compaction degree of the deepwater formation is low due to low overlying seawater density, which leads to the narrow pressure window between formation fracture pressure and collapse pressure and the corresponding narrow safe window of drilling fluid density. Therefore overflow and mud loss will occur frequently. The improper handling of the overflow and mud loss accidents can lead to blowout accident. For this reason, describing the risk level with the increase of the actual probability of accident relative to the aver- age probability, the quantitative evaluation model of well control risk under deepwater and narrow pressure window drilling was estab- lished using barrier and operation risk analysis method. Taking well burst as the initial event, a well burst event tree under deepwater and narrow pressure window was established based on the consideration of the breath effect. After the well burst, 8 events may eventual- ly produce 22 results, 7 results of which are blowout and blowout out of control. According to the established event tree, 7 preventive bar- riers are set to prevent the well burst developing to the blowout, and the influence of each barrier failure on the whole barrier system is obtained by sensitivity analysis. According to foreign literatures, the average probability of blowout in deepwater drilling is 1.209 × 10^- 5, the quantitative calculation of the risk of a drilled deepwater well has been carried out, and the calculated result is in good agreement with the actual conditions of the well, which verifies the reliability of the model. The research result can provide theoretical guidance for the well control safety of deepwater drilling.
出处
《石油工业技术监督》
2017年第2期54-59,共6页
Technology Supervision in Petroleum Industry
关键词
深水钻井
井涌
井喷
事件树
井控风险
deepwater drilling
well burst
blowout
event tree
well control risk