Mathematical modelling of borehole grouting in permafrost

Abstract

The process of borehole grouting in the regions of permafrost is more complicated than in normal climatic conditions due to the possible thawing of the frozen rock, which can be induced by the heat produced during cement hydration. In order to prevent thawing of the surrounding formation, the main conditions that should be imposed on the grouting off technology and properties of the cementing slurries are rapid cement hydration and low heat generation during chemical reaction. Mathematical model of the grouting off process in permafrost, presented in this study, accounts for heat transferred from the borehole circulating mud and heat generated due to cement hydration. The problem is solved analytically by the approximate integral-heat-balance method. As a result, the close-form solutions for the temperature field in the cemented region and surrounding formation are obtained. On the basis of these analytical solutions, analytical criteria for the borehole grouting off regimes that take place without thawing of the frozen rock are proposed. These criteria can be readily used for assessing physical and chemical properties of the cement slurries and their suitability for grouting off the borehole in permafrost. © 2004 Elsevier Ltd. All rights reserved.