Desander mini-hydrocyclones applied to the separation of microspheres and sand in non-Newtonian fluid: Efficiencies and drag analysis

In an oil well drilling operation, the control of the pressure exerted by the fluid occupying the annular region is essential for the success and reliability of this expensive operation. If the pressure exerted by the fluid is less than the pore pressure of the formation, the undesirable invasion of fluids trapped in these pores into the well will occur. If, in contrast, the pressure exerted by the fluid is very high, the fracture of the rock formation can occur, which in extreme cases can lead to the collapse of the well. In deepwater and ultra- deepwater drilling, the difficulty in controlling the pressure of the fluid is even greater since the operating window is narrower. To adjust the pressure of the fluid in the annular space, there is often a need to reduce the density of the drilling fluid. One way of achieving this goal is to add thin and low-density particles to the fluid, like hollow glass microspheres. A great recovery of these microspheres, for later reuse, is essential to ensure the economic and sustainable viability of this procedure. Mini-hydrocyclones are equipment with good potential to be applied in the recovery of this kind of solid. Thus, assays were conducted in a modular hydrocyclone to select the most appropriate geometric configuration for hollow glass microspheres separation. The results showed high microspheres (close to 80% in the overflow) and sand (94% in the underflow) total separation efficiencies. Regarding the possible drag of microspheres in the sand, the study showed that for sand feed volumetric concentrations equal to 9%, the total sand separation efficiency decreases to 68% in determined conditions. However, this did not promote significant changes in the microsphere total separation efficiency, demonstrating that sand is not responsible for the drag of hollow glass microspheres to the underflow stream.