Aging characteristics of diesel and its impact on the gelation performance of organomontmorillonite

Toward the optimization of diesel-based drilling fluids, the effects of storage conditions on the stability of diesel and diesel–organomontmorillonite (OMMT) colloids were studied using continuous oxygen, single-dose oxygen, ambient air, and carbon dioxide. Changes in diesel acidity, viscosity, aromatic content, and composition of diesel, together with the gelation performance parameters of diesel–OMMT colloids, including colloid fraction, rheology, particle size, and zeta potential, were investigated during storage. Compared with the control, diesel sample aged under continuous oxygen exhibited a substantial increase in acidity, whereas aging under carbon dioxide reduced acidity. Aging also increased the viscosity and total aromatic content of diesel, while decreasing the contents of oxygen-containing substances, olefins, and cyclic compounds. Meanwhile, the colloid fraction of the aged diesel–OMMT (100.0 mL, compared with 26.3 mL for the control) indicates that aging improves colloidal stability. At the shear rate of 0.132 s −1 , the colloidal viscosity increased from 510.43 to 53436 mPa·s, and the shear stress increased from 0.0676 to 7.087 Pa after aging of the sample subjected to carbon dioxide treatment. After eight months of storage, the carbon dioxide-aged sample exhibited a smaller particle size (1732 nm) and a higher absolute zeta potential (0.479 mV) than the sample aged under single-dose oxygen (3976 nm). These findings demonstrate that oxygen and carbon dioxide affect diesel stability through different mechanisms and that storage atmosphere substantially influences the rheological behavior and stability of diesel-based organoclay colloids, providing a theoretical basis for the application of oil-based colloids, particularly oil-based drilling fluids.