热膨胀系数对气体钻井井底岩石应力场的影响

气体钻井中高压气体通过喷嘴发生焦耳—汤姆逊效应，导致井底温度降低，井底低温影响井底附近岩石应力分布。在热膨胀系数为常数和随机变量两种情况下，研究了低温对气体钻井中井底岩石应力分布的影响。结果表明：井底温度降低，切向应力增大，径向应力减小，意味着井底温度降低，岩石变得容易破裂，有利于提高机械钻速；热膨胀系数为常数和随机变量两种情况下，应力分布趋势相同，只是数值上有所差别，热膨胀系数为随机变量时的切向应力数值大于热膨胀系数为常数时的切向应力。

Influence of the Coefficient of Thermal Expansion on the Stress of BottomHole Rock in Gas Drilling

In gas drilling the high-pressure gas results in the Joule Thomson cooling effect through the nozzle which causessignificant temperature gradient at bottom hole which should result in non-uniform reduction of compressive stress in the rockdue to thermal contraction of rock. In this paper，low-temperature impact on the stress distribution of the rock in the bottomin gas drilling the thermal expansion coefficient is random variables and constants is studies in the conditions that. The resultsshow that：low-temperature drilling fluid can significantly reduce the radial stress and increase the tangential stress in the nearbottom hole region. This stress condition makes the rock easy to fail by the crushing action of drill bit teeth，resulting is in theremarkable increase in rate of penetration. When the thermal expansion coefficient is random variables and constants，the stressdistribution in the same trend，only different in values. The tangential stress is greater when thermal expansion coefficient israndom variable than when it is a constant.