从井底岩石受力分析研究气体钻井对机械钻速的影响

采用气体钻井时机械钻速较高,目前已被钻井界普遍认可;但对气体钻井是如何提高机械钻速的研究还不多。为此,通过有限元软件对井底岩石所受应力及其垂向应力积分曲线进行分析,结果发现,气体钻井过程中井底岩石上凸,表现为类似"张力"的外张趋势,其垂直于井底平面向下应力影响范围也比常规钻井液的大,由于没有钻井液静液柱压力的压持效应,岩石开始从塑性向脆性转变,这和所预期的结果一致;这一转变更利于钻头切削面与岩石接触,提高岩石破碎效率;也就是说,如果在使用相同的钻头、钻具组合以及机械参数等作用下,岩石破碎的区域更大,钻进速度也更快。

Research on the Influence of Gas Drilling on Penetration Rate

This article analyzed the stress and vertical stress integral curve of the core of bottom hole through finite element software,we found the rock of the bottom hole was " convex" during gas drilling,and the effecting scope of the down stress was large than the conventional drilling fluid.Having no hydrostatic column chip hold down effect of drilling fluid,rock began to transit from plasticity to brittle,this was just accord with expected result.This alteration benefited the touch of the bit cutting face and rock,and improved the efficiency of rock breaking.That is to say,the region of rock breaking is larger and the rate of the penetration is also higher with same BHA and other mechanical parameter.