Particle transport and hole cleaning in wells during drilling

Abstract

The purpose of the thesis was to look at particles in different rheology to develop a methodology for measuring settling velocities in static systems. There was built a small-scale cell with an inner pipe and a discharge system. In advance there was done a feasibility test on which particles to use. As a result of this test, it was decided to use glass beads with the diameter of 0.001 m, 0.002 m and 0.003 m, and steel spheres with the diameter of 0.004 m and 0.015 m.

The fluids used were water and PAC in order to compare behavior in Newtonian versus non-Newtonian. Two different concentrations of PAC were used. Rheology and density measurements were done prior to the experiment. PAC-4g/l was heavier and more viscous than water, and PAC-8g/l was heavier and more viscous than PAC-4g/l.

The terminal velocity of the particles was determined by theoretical formulas found from literature and by looking at pictures from the camera recordings. Both regular and high-speed camera was used. The results from the experiment in water show that the experimental velocity is coherent with the theoretical velocity.

There was done a second feasibility test on the fluids with different rheology. The velocities and movements of particles of each size were studied, both in single and cluster movements. Here it was ascertained that the velocity decreases with increasing viscosity of the fluid. It was also observed that particles moving together in clusters have a higher velocity than a single particle. As a result of this test, it was decided to look at a two-phase system, where Bayol 35 was used as an oil solution and PAC-4g/l was used as a water solution. The results from this experiment showed similar velocities as previously found for water and PAC.