The Cooling of a Borehole Drilled into an Area with a High Thermal Gradient
Abstract
Drilling technology is limited to temperatures less than 350° C. When drilling into magma, temperatures in the 350° - 1100° C range will be encountered, therefore the cooling of the drill bit environment to a temperature of approximately 350° C must be accomplished. The heat transfer properties of a fluid flowing through a single pipe were investigated, and it was found that the temperature-depth profile in the fluid was a function of the temperature difference between the fluid and wall rock and an energy balance parameter which depends on the dimensions of the hole and the properties of the fluid. It was found that as the energy balance parameter was decreased, the hole was cooled more efficiently. This was done most efficiently by increasing the diameter of the hole.
This analysis was extended to a concentric cylinder model analogous to the drilling operation. Here two differential equations were found and solved simultaneously. It was found that the heat transfer at the inner boundary was more critical to the temperature near the drill bit than the heat transfer at the outer boundary. It was also found that for an energy balance parameter sufficiently small, the borehole can be cooled significantly at shallow depths.
Description
Program year: 1978/1979Digitized from print original stored in HDR
Citation
Dyer, Robert Alan (1979). The Cooling of a Borehole Drilled into an Area with a High Thermal Gradient. University Undergraduate Fellow. Available electronically from https : / /hdl .handle .net /1969 .1 /CAPSTONE -HelmsB _1990.