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Abstract
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In this study, hydrophilic gilsonite fine particles were produced by reaction of natural gilsonite with a mixture of sulfuric acid and nitric acid followed by a planetary ball mill process. The hydrophilic gilsonite was characterized using FTIR, XRD, FE-SEM, DLS, elemental analysis, and mass spectroscopy. All experiments showed that the characteristics of the hydrophilic gilsonite, due to its surface modification, were different from those of natural gilsonite. Moreover, hydrophilic gilsonite molecules were dispersed in water as fine particles with an average diameter of 300 nm without adding any dispersant. The effects of hydrophilic gilsonite on the rheological properties as well as the fluid loss of the water-based drilling mud were investigated before and after the hot-roll process. The results showed that simultaneous adding of 10 g of hydrophilic gilsonite fine particles to the base fluid and reducing the starch concentration to half of its initial value resulted into the best composition for efficient water-based drilling mud. In this case, the rheological properties of the mud were stabilized with a minimum change in the decrease of the yield point, foam formation was prevented after the hot-roll process, and the pH of the system was stabilized in a suitable range at high temperatures. Moreover, this composition could reduce the fluid loss by 50.8% and the filter cake thickness by 66.7% in low-temperature, low-pressure conditions, while the fluid loss
reduction was 75% in high-temperature high-pressure conditions. Moreover, the results revealed that hydrophilic gilsonite was an effective additive during the 16 h hot-roll process.
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