气体钻井井下燃爆界限计算模型

Calculation Model of Downhole Explosion for Gas Drilling

为明确气体钻井过程中引发井下燃爆的原因,确定井下混合气的燃爆界限,根据现行气体钻井施工规范及现场从业经验,归纳出气体钻井施工时环空不畅或封闭、钻具与地层岩石的摩擦生热、钻头破岩产生火花是引发燃爆的原因,并结合燃烧与爆炸学理论知识从引燃方式入手,建立了以热自燃、热板点火、热球点火和火花点火为引燃能量表现形式的燃爆界限计算模型。以A井施工为例,该模型可根据钻井参数变化动态计算不同井段的燃爆界限,为及时调整钻井方案和防控井下燃爆事故提供了依托。

In order to clarify the cause of gas drilling downhole explosion during and the explosion limit of downhole mixed gas,according to the current gas drilling operation specifications and field experience,it is concluded that the annulus is not smooth or closed,the heat generated by the drilling tool and the rock friction,the sparks generated by the drill bit breaking the rock are the reasons for the downhole explosion.Combining the theoretical knowledge of combustion and explosion theory,a calculation model for the downhole explosion limit was established with thermal spontaneous combustion,hot plate ignition,hot ball ignition and spark ignition as the forms of ignition energy.Taking the construction of well A as an example,the model can dynamically calculate the explosion limits of different well sections according to the changes in drilling parameters,which provides a basis for timely adjustment of the drilling plan and prevention and control of downhole combustion and explosion accidents.