Experimental Observation of Suspension Sedimentation in a Horizontal Annular Tube

Abstract

This study presents an experimental exploration of suspension sedimentation within a horizontal circular annulus, as a model for cement paste. The integrity of hardened cement sheaths with no pre-existing defects has been extensively studied for the oil and gas, but geometrical defects coming from cement placement has not been discussed, motivating this study. We mimic the water-cement suspension in the annular space with silicone oil and soda lime glass beads ranging in size from 25 to 500 μm. The annular cylinder has inner and outer diameter of ca. 90 and 140 mm, respectively, and a thickness of ca. 20 mm. It is filled the suspension, the oil representing the water and the beads the cement particles. The concentration of these beads is systematically varied, between semi-dilute (5%) and dense (ca. 45%) to reach typical value of cement particle concentrations. The experimental procedure involves initially shaking the circular annulus to reach a uniform particle distribution in the cell, before allowing it to settle undisturbed while recording videos with a Canon EOS 80D camera at 30 fps. This approach allows us to observe how particles settle. Specific areas within the circular space, i.e., the poles and the equator region, are of particular focus. Furthermore, different particle tracking and velocimetry techniques were used to generate velocity profiles and monitor individual and collective motion of particles. In summary, this study combines experimental investigation of suspensions, imaging and image treatment techniques to deepen our knowledge of particle sedimentation in horizontal circular annuli, which can help improve how we seal horizontal oil and gas wells with cement.