Enhancing the Solidification Between Mud Cake and Wall Rock for Cementing Applications: Experimental Investigation and Mechanisms

In conventional cementing operations, the mud cake on the well wall cannot be completely removed， which can easily lead to annular channeling. In order to reduce the influence of loose and fragile mud cake on cementing, a kind of mud cake curing agent is used to effectively improve the curing quality of mud cake and rock. In this article, the mud cake compressive strength are tested by compression-testing machine. The samples are analyzed using X-ray diffractometer (XRD), scanning electron microscopy (SEM), and energy disperse spectroscopy (EDS). The results showed that the cementing agent can significantly improve the cementation strength between mud cake and wall rock. A variety of hydration products were resulted such as CaAl₂Si₂O₈ · 4H₂O, Ca(SiO₄)₂(OH)₂, and Mg₄Al₂(OH)₁₄ · 3H₂O, as revealed from the XRD analysis. In addition, it was found that the formation of hydration products is the main reason for the increase of cementation strength. The flocculent inclusions filled with solid particles are formed on the solid particles of the mud cake, which makes an integrated cementation at the interface between mud cake and wall rock. A large amount of cations including Ca²⁺, Mg²⁺, and Al³⁺ are collected at the cementation interface, which is the basic condition for various hydration reactions and helps to enhance the cementation strength of the mud cake and rock interface.