Experimental and numerical simulation of cuttings transportation in coiled tubing drilling

• A computational fluid dynamics model simulated the cuttings transportation.
• The model could accurately predict minimum transportation velocity.
• A flow loop was built to validate the CFD results.
• Higher viscosity fluids distribute the cuttings more in the annulus space.
• Generally, bigger cuttings require more energy to be transported in deviated holes.

Coiled tubing technology (CTT) showed its capabilities in oil and gas (O&G) drilling in many cases. Some of the advantages of CT drilling are rapid mobilization/demobilization and rig up/down times, faster tripping in and out of the hole, small hole size capability, faster drilling operation, and less environmental footprint. Because the CT does not rotate, a down-hole motor/turbine, which needs high flow rate, is required to rotate the drill-bit. The cuttings transport in the small size annulus space is the core part of this research study. This was done through both laboratory experiments using a flow loop and numerical modeling.The results of flow loop experiments determined the minimum transportation velocity (MTV) to effectively bring all the cuttings to the surface. Directional boreholes were tested and the effect of cuttings size as well as mud properties was investigated. Testing actual cuttings in CT drilling presented different results than those observed in the literature for conventional O&G drilling. The different outcomes, for instance on the effect of rheology on cuttings transportation, necessitates conducting this research to develop a model for cuttings transportation in CT drilling.Computational fluid dynamics numerical simulation with Eulerian Granular approach was applied in this study to investigate the effect of different parameters in cuttings transportation. The simulation results were validated against the experimental results of the flow loop. Various flow patterns were simulated by changing different parameters.