Effects of Silica Fume Nano-Particles As Micro Annuli Additive on Calcium Oxide Expanded Cement for Gas Well

Unlike oil well, gas well cement formulation requires special additives to take care of the microannuli that may arise as a result normal water cement ratio. The normal water cement mixing ratio usually yield low volume of cement slurry with attendant problem, chief of which is shrinkages. Hence, calcium oxide is used to expand the cement to mitigate against shrinkages and subsequently increase the slurry’s yield. The expanded cement ensures the integrity of wellbores and prevents the migration of fluids into the wellbore.Traditional oil and gas well cements are composed primarily of Portland cement, water, and admixtures. However, concerns over environmental sustainability and resource depletion have driven the exploration of alternative cement additives, such as pozzolanic materials.Pozzolanic materials, such as silica fume, rice husk ash, and palm oil fly ash, have emerged as promising alternative additives in formulating cement slurries due to their sustainability benefits and potentials to enhance cement properties.The fracture pressure of the weakest formation is usually considered when formulating cement slurry. In formulating the cement slurry under investigation, a fracture pressure of slurry density of 15.4 ppg equivalent was used.The normal mixing ratio of 0.44 as per API standard would give 15.8ppg. With a specific gravity of 3.25, calcium oxide is a density increasing material which allowed for the use of considerably lower amount of water, silica fume is a density reducing material, hence the use of higher amount of water. The incorporation of calcium oxide (25 % BWOC) and silica fume (15 % BWOC) lowers the slurry density to 15.4ppg. The results obtained at 100 Bc consistencies showed a gradual decrease in thickening time with increase in temperature in both the expanded and nonexpanded cements. The porosity of the expanded was determine using fresh and saline water and was found to be lower than 0.05 % which shows that the silica fume acted on the micro spaces in the cement.