Application of Qusaiba Kaolinite Clays as Secondary Cementitious Material in Oil Well Cementing

The oil and gas industry, constituting 90% of Saudi Arabia's exports, relies on essential operations, including oil-well cementing. This crucial process ensures zonal isolation and wellbore structural support. While traditional cementing involves Saudi Class G cement, water and additives, recent attention focuses on secondary cementitious materials for enhanced mechanical properties and durability. Kaolinite is a type of clay mineral investigated as a supplementary cementitious material in various applications, including concrete and mortar. The objective of this study is to use Qusaiba kaolinite as a secondary material in oil and gas wells cementing. Six heavyweight cement samples with different kaolinite concentrations were prepared under high pressure and high temperature (HPHT) conditions. The effects of incorporating several kaolinite dosages on the cement's segregation, microstructure, mechanical, elastic, and petrophysical properties were assessed. The results of this study revealed that 1% by weight of cement (BWOC) is the optimum concentration of kaolinite to be used. Using kaolinite improved the mechanical strength of the cement, where both the compressive and tensile strengths of the cement were increased by 13% and 73%, respectively, when adding kaolinite. It also resulted in a 6.4% reduction in Young’s modulus and a minor increase in Poisson’s ratio, indicating improved cement elasticity. Cement segregation was also reduced by 74.4% after adding kaolinite, as noted in the direct density variation method and confirmed by the CT scan. As indicated by the SEM images, the ability of the kaolinite to fill the pore spaces reduced the cement permeability by 74.4% for the samples prepared with kaolinite.