This research focuses on the three-phase separation of oil-water-solids that may be encountered in oil-bearing media. Developing a process to perform this three-phase separation downhole in the oil-bearing media leads to significant financial advantages. This research involves the use of a hydrocyclone unit to perform the separation. The unit is then used in conjunction with a centrifugal separator to further purify the streams. A separation efficiency is developed to predict the maximum separation possible for each of the phases present in the system. At specific operating conditions, a good separation is demonstrated for removing solids, as well as the separation of the liquids into two separate streams. The removal of the solids, with the remaining liquids exiting together in a separate stream, is also accomplished using the hydrocyclone unit. The research spans a range of feed compositions to simulate the possible process fluids that may be generated in an oil production process. This research indicates that the hydrocyclone can operate very efficiently in the three-phase system of a downhole oil-bearing media. Performance of the hydrocyclone can also be readily predicted for the solid and liquid separations.