空气钻井井下燃爆控制技术探讨

DISCUSS ON PREVENTION AND CONTROL OF DOWNHOLE EXPLOSION DURING AIR DRILLING

空气钻井条件下,若钻遇地层含油气流体,且温度和压力满足井下燃爆条件需要,易发生井下燃爆事故。井下燃爆不仅造成钻具、套管被烧毁破坏,还会造成井眼破坏,后续处理困难,造成井眼报废等,其成为了阻碍空气钻井技术的发展瓶颈。文章从燃爆极限、点火方式着手,分析了空气钻井井下燃爆机理,提出了防止井下燃爆控制措施,首先是详细研究地质资料,尽量避开油气层段;在空气钻井作业期间,防止井下燃爆的重点是对井下可燃的流体进行监测,及时发现,及早转换钻井方式;在钻具组合中加入灭火阀也可达到阻燃的目的;在可能出气的层段采用氮气钻井,是避免井下燃爆的有效手段;雾化钻井、泡沫钻井等技术在控制井下燃爆方面也有一定效果。

Air drilling tends to cause downhole fires when drilling through oil/gas-bearing formations and the downhole temperature and pressure within the explosion and burning range. The blasting not only leads to the loss of drilling tools and casings,it will also damage the hole,making subsequent disposal hard or even resulted in well abandonment,which has become a bottleneck for air drilling technology development. Starting from explosion limits and ignition modes,the downhole explosion mechanism of air drilling is studied,and downhole explosion prevention and control measures are proposed here in this paper.The first thing is to study geological information thoroughly,trying to avoid the petrolum layers. While during air drilling,the major thing to prevent blasting is to monitoring the flammable fluids. Once the flammable fluid detected,to transform the drilling mode is very important. And adding the fire-prevention valve into BHA can also help to prevent fires,nitrogen drilling adopted to drill layers which may have gas is also an effective way,and mist/foam drilling is helpful for downhole explosion prevention and control.