邛崃1井氮气钻井事故分析(Ⅱ)——事故过程的还原及教训

Analysis on the nitrogen drilling accident of Well Qionglai 1,western Sichuan Basin(Ⅱ):Restore of accident process and lessons to learn

上文针对邛崃l井氮气钻井中的井喷失火事故,对构成事故的重要事件进行了分析。在此基础上.基于事故调查资料、实时录井资料和必要的计算与数模分析结果,按照安全工程学中故障树的分析原则,分析了构成邛崃1井氮气钻井恶性井喷失火事故的重要事件的各种可能组合、发生概率和时间顺序,还原了事故的全过程,并完整地解释了综合录井数据所表达的事故内幕。研究结果认为:①该次事故的客观原因是严重"岩爆"的发生及其诱发事件;②主观原因是该井排砂管线不能适应"岩爆"产生的大股碎屑而堵塞,进而由堵塞产生井口高压引发排砂管线爆裂,导致失控井喷和着火。最后,基于对裂缝性致密砂岩气层中实施气体钻井时井下岩爆是一种客观的、必然的现象的认识,提出了需要进一步改善排砂管线、井口组合和钻具附件特性的技术建议,以从根本上防止井下岩爆诱发的地面事故。所得到的认识与建议将有助于扭转该事故对气体钻井技术所造成的不利影响。

After discovering and analyzing the root of causes was discovered and analyzed for the drilling accident of Well Qionglai 1 in the paper part I , we will restore the accident process to draw the lessons from that in this paper part Ⅱ. Based on the investiga- tions, well log data and the necessary calculated and simulated results, and according to the analysis method of the fault tree of safe engineering, any possible compositions, possibilities and their time schedule of the events of the accident were analyzed, the process of this accident was restored, and the implicit meanings behind the logging data were revealed. The following conclusions were a- chieved. First, the induced events leaded to rock burst, which was the objective causes of the accident, while the subjective cause of the accident was that the discharge pipeline could not bear the flow burden of the chips from rock burst so as to be blocked by the chips. Then, the blocking of discharge pipeline caused high pressure at wellhead and front part of discharge pipeline, resulting in the discharge pipeline burst, well blowout and flared fire. Last but not least, the rock burst in gas drilling in fractured tight sandstone gas zones was objective reality and not avoidable, but the inducement events resulting from rock burst could be controlled reasonably so that the potential accident would be avoided effectively. On this basis, some technical proposals were presented here to further im- prove the explosion bearing capabilities of discharge pipelines, wellhead equipment and drilling tools. The papers of both part I and Ⅱ will help us draw lessons from those painful accidents and have a better understanding of gas drilling.