|
Abstract
|
Proper annular sealing is imperative for isolating wellbores, preventing leaks to the surface and protecting groundwater during oil drilling operations. Cementing between the casing and borehole is crucial, yet cement failures potentially risk disastrous leaks and massive economic losses for exploration and production companies. Novel additives such as gilsonite nanoparticles (NPs) present a promising solution to enhance cement integrity. This study investigated the effects of incorporating gilsonite NPs on cement performance under conditions mimicking typical downhole environments. Cement slurries were formulated using a water-to-cement ratio of 0.44 and a calcium chloride content of 2% by weight of cement (BWOC). The concentration of gilsonite NPs varied from 0.01 to 0.04% BWOC. The slurries were tested for rheology, morphology, crystallization, and compressive strength following American Petroleum Institute guidelines and compared to the base slurry. Significant cement property improvements were achieved with gilsonite NPs. The addition of 0.04% BWOC gilsonite resulted in a significant 53% increase in compressive strength, from 4777 (base) to 7306 psi, after curing at 100 °C and 1000 psi. Real-time strength development showed an accelerated setting and higher ultimate strength. Fluid loss was reduced by 32% compared to that of the base slurry. The slurries exhibited enhanced shear-thickening behavior and gel strength. Young’s modulus decreased, while Poisson’s ratio increased, indicating improved flexibility. Porosity and permeability decreased by 29 and 76%, respectively, at 0.04% concentration. Microstructural analysis revealed a denser, more compact cement matrix with improved particle bonding. Further work should examine the performance following accelerated age testing. The mechanical, rheological, and physical enhancements could enable long-term cement sheath integrity over decades of good life, preventing leakage and associated consequences.
|