Inderscience Publishers

Inderscience Publishers

Thermal stress on bottom hole rock of gas drilling

Gas drilling has higher penetration than mud drilling. The greatest reason for this phenomenon with gas is that the gas is greatly cooled by expansion as it passes through the bit and thereby cools the bottom of the hole. The thermal stress at bottom–hole occurs during this process. The concept of thermal crushing of rocks is analysed in this study. The theoretical methods are developed to analyse thermal stresses and fragmentation induced by cooling of rock. Then, the numerical computation is conducted for the thermal stress equations with the numerical result simulated for the temperature field at the bottom hole to explain the reason of high drilling rates in gas drilling. Furthermore, an experiment was conducted to verify the theory. Therefore, the theories and simulated results in this paper have a guiding signification for best understand the technique and possibly to extend its economic advantage still further. [Received: September 23, 2011; Accepted: November 20, 2011]

Keywords: gas drilling, low gas temperature, thermal stress, strain energy, fragmentation, numerical computation, bottom hole rock, thermal crushing, rock crushing, simulation, temperature field, drilling rates

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