Evaluation of Qusaiba Kaolinitic Shale as a Supplementary Cementitious Material in Lightweight Oil-Well Cement Formulation.

Metakaolin is a supplementary cementitious material produced through the calcination of kaolinitic rocks. The scarcity of high-grade and commercial quantities of kaolinitic-based rocks makes metakaolin expensive. The objective of this study is to evaluate the feasibility of the kaolinitic shale obtained from the mud-rich Qusaiba Member of Saudi Arabia as a source of metakaolin. The rock was dried, ground, and passed through a 75 μm sieve to obtain a fine powder. The powder was calcined at 1202, 1292, 1382, 1472, and 1562 °F for 1 h. The optimum calcination temperature required to convert the material into metakaolin was found to be 1562 °F using X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetry analysis techniques. The analytical techniques indicated that the kaolinitic shale is of high grade and less ordered, which would make it an excellent source of a highly reactive metakaolin. Cement systems designed at 12.5 ppg (1.50 g/cm 3 ) with the metakaolin produced from the Qusaiba kaolinitic shale as 30% cement replacement exhibits mechanical properties that would be ideal for downhole oil-wellbore applications.