| dc.description.abstract | Well abandonment operations can be expensive and time consuming, and thousands of wells will need to be permanently plugged and abandoned off the coast of Norway in the coming years. One potential cost-cutting measure during P&A operations is to leave the majority of the production tubing in the well, which would save significant rig time. However, a big problem with this technique is whether the cement can adequately displace the original fluid, due to tube centralization issues and possibly adverse flow dynamics in the annulus.
In this thesis we present an experimental study of annular displacements and effects of inner pipe vibration. This experimental study serves as a benchmark investigation regarding this vibration-tool when performing through-tubing abandonment. Thus, only Newtonian fluids are considered. The focus is on the effect of eccentricity and the effect of vibration. In an experimental setup, the displacing fluid is pumped into the annulus and displaces the original fluid. The density difference is achieved by adding sugar and salt as weighting agents to the displacing fluid. The fluids are scaled and modelled to simulate real field conditions. In several runs, the eccentricities 0, 0.46, and 0,82 are combined with different vibration intensities (Hz): 0, 2.5, 5, and 10. When the vibration is low and medium, it has an negligible effect on the annulus displacement process when compared to non-vibrating experiments. However, when the vibration intensity is set to 10Hz, we see a significant effect of the displacement process. The high level of vibration enables fluids to flow circumferential from the narrow side to the wide side and vice versa. | |
