Characterization by microcomputed tomography of class G oil well cement paste exposed to elevated temperatures

During the life cycle of an oil well the cement paste is subjected to various forms of deterioration which affect its durability. One of these forms of deterioration is due to the effect of elevated temperatures that can reach 350 degrees C. In the present study, class G cement paste cylindrical specimens were subjected to temperatures of 100 degrees C, 200 degrees C and 450 degrees C for 1 h. The temperatures of 100 degrees C and 200 degrees C were chosen due to the in service operation of an oil well while 450 degrees C was selected based on the results of previous studies. X-ray computed tomography (microCT) was used to generate three-dimensional images of the internal structure of the specimens before and after the heating procedure, and to quantitatively assess the evolution of pores and cracks. X-ray diffraction (XRD) and mechanical tests were performed with the intention of making a correlation with the results of microCT. The increasing appearance of cracks with increasing temperature was evident and expected. In this study this growth could be visualized in 3D and quantified. Finally, as a partial conclusion, the Class G Oil Well Cement Paste can be used for operations with in service temperatures up to 200 degrees C, as it showed small amounts of narrow cracks and the mechanical tests showed that the strength of this material did not decrease.