Grout‐Induced Temperature Rise Surrounding Wells

Abstract

ABSTRACTCement grout surrounding a well casing generates heat, called heat of hydration, as it hardens. This heat can raise the temperature of the casing‐grout‐soil system significantly. Because the strengths of plastic casing materials decrease relatively rapidly with increasing temperature, it is important to have some idea of the temperature increase to be expected. Solution of the radial heat‐flow equation predicts temperature rises at the outer casing boundary of 9°C (16.2°F) to 55°C (99°F) as the grout envelope around a 6‐inch, water‐filled casing varies from 1.5 inches to 12 inches. The time required for the peak temperature to be reached varies from 7 to 22 hours. The temperature increase is relatively insensitive to casing diameter and thermal properties of the casing and soil. It is relatively sensitive to the type of cement used in the grout and the material filling the casing while the grout is curing. All types of plastic casing have been used successfully for years. This is due partly to the fact that in most grouting operations from the bottom up, forces on the casing are such that there is little or no tendency for collapse. However, if an air‐filled, plastic casing were grouted from the top down, heat‐induced collapse would be much more likely, particularly in zones where caving took place during well drilling.