Cuttings lifting improvement of different drilled cutting sizes using polypropylene beads with and without pipe rotation

Abstract

Directional wells become a successful field-development method to meet higher energy demands worldwide and to increase the recovery factor. However, the most challenging problem encountered in drilling such wells is inefficient wellbore cleaning. Therefore, this study was conducted to investigate the performance of polypropylene copolymer (PP) beads in water-based mud to hamper the wellbore cleaning issue. The study includes sample characterization and investigation of the effect on mud rheological and filtration properties. The presence of ethylene in the PP beads composition has led to an increase in their melting point up to 159°C (318°F), which is higher than typical reservoir temperature reported in Malay Basin. Therefore, the mud rheological and filtration properties tests were conducted up to 250°F only. Also, the PP beads were discovered to degrade at 278.59°C (533.46°F). The effect of hole cleaning have been scrutinized using a flow loop test section (20-ft of transparent PVC having a 3.042-inch ID simulated as wellbore, and a rotatable Class B carbon steel with 1.346-inch OD which simulates a drill pipe) and were compared with basic water-based mud (WBM) at various wellbore inclination angles (from 0° to 90°) and pipe rotation speed (from 0 to 150 rpm). The experimental work was executed using several PP beads concentrations (from 0 to 10 ppb), which were introduced in water-based mud, and their performances were compared with basic WBM in terms of rheological properties and cuttings transport performance (CTP). CTP is an extent measure to lift unwanted cuttings out of the wellbore and was performed by employing 0.25% (by volume) of different cutting sizes, ranging from 0.5 to 4.0 mm, in the prepared mud. The comparison also made based on PP beads concentration, cutting sizes, wellbore angles, and pipe rotation speed with basic WBM. The experimental results showed that the rheological properties are slightly increased when mingling the PP beads with mud, and the opposite outcome was obtained for filtration properties. Furthermore, the CTP improved once commingled with PP beads for all different cutting sizes and hole angles due to the buoyancy and impulsive effects. This experiment also detects the critical angle between 30° to 60°, which indicates by decreasing of CTP and the lowest CTP was found at 60°. Since buoyancy and impulsive force at the horizontal hole is negligible, a combination effect of pipe rotation, mud rheology (mud viscosity of 15 cP) and flow regime (turbulent flow) has rendered improvement towards lifting performance. Besides, smaller cuttings appeared to be easier to be transported compared to the larger cuttings in both vertical and deviated wells, for each rotary speed and drilling muds. Additionally, pipe rotation contributes to cuttings transport by increasing the CTP for all experimental variables. Conclusively, the presence of PP beads in the mud has reduced the cuttings concentration in the wellbore for all cutting sizes and hole angles, and thereby enhances the CTP. Henceforth, making the PP beads a promising additive for drilling mud in lifting drilled cuttings out of the hole effectively.