Accumulation of fine particles in invert emulsion drilling fluids is known to adversely affect drilling performance and pose severe risks such as “stuck pipe”. Solid control systems fail to separate these particles mainly because of gelation and stable oil wet particles. As a result, the performance characteristics of the drilling fluid degrade over time. When a drilling fluid no longer meets operation requirements, or it is no longer cost effective to treat the fluid, the fluid is replaced and a mud changeover is performed and the old drilling fluid becomes a waste. This research looks into the technologies capable of removing fine particles and recycling invert emulsion fluid to extend operation life or facilitate disposal.
Two novel technologies (i.e. microwave and ultrasound) are investigated to enhance phase
separation and fine particles removal in invert emulsion drilling fluids. These two methods selectively target emulsion droplets and fine particles by heat generation (microwave) and orthokinetic, acoustic wake effect and mutual radiation pressure interaction mechanisms(ultrasound). In this thesis, invert emulsion drilling fluid was first contaminated with rev dust
particles and aged for 24 h to simulate used drilling fluid. The contaminated samples underwent two treatments (i.e. microwave and ultrasound) for 5 minutes and centrifuged for 20 min at 3000 RCF, left at a standstill and visually observed for phase separation. The electrical stability and density of supernatant oil were measured along with microscopic analysis to provide an understanding of the mechanisms of phase separation after microwave and ultrasound radiation.
Microwave was proven to be very effective for dewatering invert emulsion and phase separation. More than 50% of the initial base oil in the invert emulsion was recovered by the microwave treatment after centrifugation. Ultrasound was not as effective as microwave in terms of phase
separation; however, very large aggregates of rev dust particles were formed after 5 min of sonication. Both methods greatly improved the phase separation and centrifugation efficiency.