Turbodrill is a type of hydraulic axial turbomachine that rotates a bit by the action of the drilling fluid on turbine blades, which converts the hydraulic power provided by the high pressure from drilling fluid into mechanical power through turbine stages. The evaluation of hydraulic turbine performance characteristics are important to define feasible rotational speed and mass flow to attend the bit torque requirements during drilling through the post-salt and salt layers. As a result, optimum operational parameters are proposed for gaining the required rotational speed and torque for post-salt environments. The turbine motor presented in this study was established by design methods based on classical aeronautical turbomachinery blade profile to supply 30k Newton-meters (Nm) of torque requested by a polycrystalline diamond compact (PDC) bit to power the complex heterogeneous layer of rock. The performance evaluation of this innovative hydraulic turbine with 200 stages was carried out using computational fluid dynamics (CFD). The simulation considers two different drilling fluid types, sea water and brine. Besides, different flow rates were considered to investigate how velocity vectors, pressure profile, output power and other performance parameters are affected. Due the large amount of data, the first and second stages of the turbine have been used to predict the performance characteristics. This assumption gives interesting results and avoids too heavy computational costs. A commercial CFD solver (ANSYS CFX 15.0®) was used to calculate the governing equations based on Reynolds-Averaged Navier-Stokes (RANS equations) with the addition of turbulence model. The two-equation Shear-Stress Transport (SST) turbulence model was used to account the effects of flow eddy viscosity.

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