Enhancing the durability of oil and gas wells using metakaolin-modified cement: An investigation of compressive and shear bond strengths at 95 and 180 °C

This study is based on two laboratory experiments conducted to investigate the effects of different dosages (0 %, 5 %, 15 %, 25 %, 35 %, and 45 %) of Metakaolin (MK) on the compressive and shear bond strength of a modified G class oil well cement. The pastes were created and subsequently cured at two distinct temperatures, 95 °C and 180 °C. Following this, they were hydrated for varying durations, up to a maximum of 45 days. The microstructure and characteristics of hardened cement pastes were investigated using seven tests, namely: rheology, thickening time, compressive strength (CS), shear bond strength at the cement formation interface (CFI), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The test results of the selected samples (MK0, MK5, and MK35) cured at 95 °C and (MK0, MK25, MK35, and MK45) cured at 180 °C for 45 days show that both compressive and shear bond strength increased with extended aging time, particularly at 95 °C. The recorded CS of MK5 and MK35 is 20.4 % and 32.99 %, respectively, while the SBS is 16 % and 14 % respectively. At a temperature of 180 °C, the CS for MK25, MK35, and MK45 is 22.2 %, 49.11 %, and 124.89 %, respectively, while the SBS is 27 %, 48 %, and 79 %, respectively. These values are more significant than the CS and SBS of MK0 at the same aging duration of 45 days. The partial replacement of cement pastes with metakaolin led to the development of cementitious materials with lower porosity and increased strength. This improvement can be attributed to the creation of stable hydration products and a dense microstructure. Alongside, the presence of MK particles led to a reduction in porosity due to their ability to fill empty spaces. Based on this investigation, it can be concluded that using the modified OPC with a partial replacement of MK is more effective and ideal for deep and high-temperature wells.