Full-Scale Solids Control Testing of a Light Density Hollow Glass Beads Drilling Fluid

Light density drilling fluids with hollow glass beads (HGB) are growing in applications for drilling depleted formations with minimal losses and increasing rate of penetration. However, there is a lack of studies on how best to utilize typical solids control equipment, as current practices and procedures based on barite weighted muds are inefficient. We report a systematic full-scale test program to study and optimize solids control efficiency with shale shaker, hydrocyclone and centrifuge with such fluids. A non-aqueous-based hollow glass bead drilling fluid was formulated in the lab and a large batch (>40bbl) was prepared and tested using field scale solids control equipment. The inlet and effluent streams were monitored for density, particle size distribution, retort, rheology, and rheological properties and evaluated to determine the optimal equipment conditions to maximize solids control efficiency while minimizing loss of beads in the discharge stream. Variables included shaker screen sizes, flow rates and deck angles, hydrocyclone flowrates and operating pressures, centrifuge flowrates, differential speeds and other parameters. The amount of glass beads in the fluid was also varied. The drilling fluid was contaminated with a variety of sized solids which mimic drill solids. Based on the data gathered, effective procedures were developed for monitoring hollow glass beads and drill solids in each stream. Through the systematic test program, conditions could be identified to achieve high solids control efficiency from the shale shaker, the hydrocyclone, and the centrifuge. This was achieved at hollow glass beads concentrations of around 11% and 22% by volume. While some previous field experiences had indicated severe challenges with centrifuge usage with these fluids, effective centrifuge operation could be demonstrated once the proper settings were identified. Overall, the testing results showed that most of the drill solids can be removed using conventional solids control equipment and fluid properties (e.g. rheology, fluid loss, etc.) can be maintained at desired levels without the loss of any significant amount of beads with the discharged solids. Since the beads are lighter than base oil, their behavior in the solids control equipment is quite different from conventional solids. As such, equipment procedures and conventional settings had to be updated or changed. It was demonstrated that high solids control efficiency can be achieved even at high bead concentrations. This work addresses a barrier in the field application of these fluids and points towards practices that allow optimizing the application by minimizing drilling fluid dilution.