Study on effects of metakaolin on the silica-cement slurry performance under ultra-high temperature conditions

In oil and gas exploration and development, the complex working conditions of high temperature and high pressure are increasing, and the strength decline of silica-cement often occurs under such conditions. In this work, the metakaolin influence on the mechanical properties and micro-structure of silica-cement at 240 ℃ and 21 MPa condition is comprehensively studied. XRD technique investigated the chemical composition of cement crystal phase, and SEM observed the micro-morphology of high temperature cement. Results showed that the loading metakaolin has reduced porosity by 12.86%, air permeability while greatly increased nanopore (＜50nm) by 36.47% and increased nanopore (＜10 nm) by 10.34%. Thus, the cement permeability reduced greatly or its anti-channelling enhanced, that is, such results improved the comprehensive performance of cement slurry. These observations, combined with the previously reported the remarkable enhancement of the MK cement compressive strength, represent a major step toward the development of strength retrogression-resistant material at high temperature.