Experimental Investigation of Flow Velocity Dispersion in Annuli

Deviated well sections are common in modern well construction. In mature areas like the North Sea region, practically all producers or injector wells will have highly deviated sections. These wells must be completed in an optimal manner including annular barrier integrity. This is important for zonal isolation through all stages of the well’s life cycle. Since all wells must be permanently plugged before abandonment it is important to ensure that annular barriers are designed with a long term perspective and not only to minimize construction time and cost. Controlled laboratory environments with various fluid compositions and flow parameters are important to develop, validate and improve models and practices. Cement displacement is normally the objective for such studies. Due to selection of fluids, data for casing cleaning operations are in reality derived. Fundamental flow properties are investigated qualitatively. Water with and without viscosifiers is used to displace similar fluids from the annular section. The effects of inner pipe rotation are included. It is shown how this gives fundamental data providing a relevant background for understanding displacement processes. The experiments have been performed in a flow loop that consists of a 10 meters long test section with 5″ OD transparent pipe inside a 6,5″ transparent pipe. Experiments were performed with concentric and eccentric horizontal annulus and both with rotating and non-rotating inner pipe. The applied flow loop dimensions are designed so that the results should be relevant for highly inclined sections in field operation.