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

Key words: gas drilling, thermal stress, gas drilling stress in the rock, low-temperature, coefficient of thermal expansion