Two dedicated flow rigs have been established as part of previous projects at UiS. The first one was made to study liquid – particle flow as with cutting in near horizontal wells. A second project focused of automated pressure control (MPD, Carlsen 2012) in cases of gas kicks and blow-out prevention. A master project developed a small scale rig for study of bed dynamics with rotating drill pipe.
During the first project (Rabenjafimamantsoa) the focus was on determination of dynamics of the cutting dunes and the interaction with the drill mud. It was found that the dynamics is much more complex than described in the model by Doron and Barnea. Formation of dunes at low and moderate flow velocities modifies both extended (axially) as well as locally, both the cuttings concentration as well as hole cleaning efficiency, and the frictional pressure gradient.
A variety of different secondary flows have been identified in these previous works which modify the traditional lifting mechanisms and also introduce other shearing and friction mechanisms. It will be important to see how these mechanisms depend on particle loading, pipe inclination and presence of other phases (oil-water and gas-liquid) in addition to the rheological parameters and drag reducers. It is known that pipe rotation and agitation via various modes of drill string movement increases cleaning efficiency and the effect of these should be evaluated in terms of basic flow mechanisms, turbulence characteristics and bed properties.
Also “chemistry”, via surface active agents and agglomeration enhancement is likely to have a major impact - in addition to more mechanical types like viscous pills.
In addition to traditional pressure measurements and flowmeters ( for gas and liquids), the flow rigs have been gradually developed, and are now equipped with advanced instrumentation
These include Laser – Doppler Anemometry for velocity measurements, and two different PIV (Particle Imaging Velocimetry) systems. One unit is dedicated for low speed flows (8 double frames per second) and a high speed (“Time resolved”) TR-PIV system with 2000 double frames per second in full resolution mode. This system also operates in stereo mode (3D) and can also do diffusion studies (PLIF) using a third installed camera. All these are Dantec-Dynamics equipment.
Two different ultrasonic systems are also in use. One is a commercial velocity profile unit (Metflow), while the other is a unit developed in a PhD project (Wrobel) to measure cuttings concentration in slurries. There is also an X-ray unit for cuttings bed measurement, and impedance instrumentation for measurement of multi-phase fluid fractions.