Abstract
Conventional methods of mitigating fluid loss in drilling operations rely heavily on chemical additives and nanoparticles, which may alter mud properties and introduce environmental and cost challenges. While the technique of ultrasonication is widely used in the oil and gas industry, especially for mixing these additives and nanoparticles into mud samples, the direct impact of ultrasonication of the base drilling mud sample alone on fluid loss behavior has been largely overlooked. This study investigates the effectiveness of ultrasonication in modifying the filtrate loss characteristics of water-based mud without any fluid loss additives. Drilling mud samples were subjected to ultrasonic treatment and compared with unsonicated samples through a series of high-pressure high-temperature (HPHT) filtration tests using ceramic disks with average pore throat sizes of 5-35 μm. The results demonstrate that sonicated mud significantly reduces filtrate loss, particularly in disks with smaller pore sizes, compared with unsonicated mud. Reductions in filtrate loss of approximately 16-45% were achieved with the 5, 10, and 20 μm pore size disks when sonicated mud was tested. These improvements were associated with the thinner and less permeable (0.2-0.4 mm) filter cakes compared to those of unsonicated mud, contributing to improved fluid retention. However, at a pore throat size of 35 μm, a significant increase in fluid loss was observed, suggesting that the benefits of ultrasonication are limited when the pore sizes exceed the effective range of the modified particle size distribution in the mud. Particle size distribution and scanning electron microscopy (SEM) data confirmed that ultrasonication fragmented and dispersed larger particles/aggregations, leading to a more stable suspension in the mud and denser mud cakes. The findings from this study demonstrate that ultrasonication of the base drilling mud alone is sufficient to improve its filtrate loss properties in most cases without the need for loss additives while being environmentally friendly and cost-effective. However, the study also implies the importance of adapting mud systems to formation properties, highlighting the critical role of the interaction between the particle size and pore dimensions in influencing fluid loss behavior and mud cake properties.