Self-healing mechanism of Zn-enhanced cement stone: An application for sour natural gas field

Abstract This study investigated the self-healing of oilwell cement stone enhanced by basic zinc carbonate (BZC) in a highly corrosive and toxic H2S-rich, high temperature and high pressure (HTHP) environment. Cement stone with 1.5% BZC had improved durability with 24.0 MPa compressive strength remaining after being exposed to the H2S-rich environment for 28 d, which was much higher than the sample without BZC. In addition, the permeability and porosity were also significantly changed and a layer-like product was observed in the microstructure as a filler phase. Quantitative thermogravimetry analysis (TGA) was used to investigate the self-healing mechanism of the BZC, and revealed that the cement matrix dissolution was controlled. Based on the compressive strength results, the predicted lifetime of cement stone in the corrosive H2S-rich environment was almost doubled with the addition of BZC.