Effect of viscosity and pressure on a poor boy downhole gas separator under continuous gas-liquid flow

Downhole gas separators are ubiquitous devices needed for the proper functioning of subsurface pumps. Contrasting its widespread use, the knowledge of its performance is quite limited. Among the various types of separators, the “poor boy” design stands as a simple, robust and easy to build device. These features have been appreciated in the oilfield during decades. Nevertheless, its performance is still not well understood. In this paper, progress on the research in static downhole gas separators are presented. A 3 1⁄2-inch poor boy type gas separator was evaluated with a continuous gas-liquid flow resembling an above perforations downhole arrangement with a 7-inch production casing. Tests were carried out using an standard ISO 150 viscous oil and air in a large scale experimental facility. As was previously found with water and air, results with oil corroborate the existence of two separation efficiency regions. The first one is a high, nearly constant, efficiency zone for low liquid flow rates. The second zone, the efficiency is an almost linear function of the liquid flow rate. The main effect of a higher viscosity is to increase the separation efficiency in a significant amount. Gas flow rate and pressure play a lesser role influencing the behavior of the separator. On the other hand, gas-liquid flow pattern arises as an important factor. An improved formula for the separation efficiency calculation based on dimensionless parameters is provided to be used for a wide range of conditions. This formula is suited for continuous flow downhole pumps such as progressing cavity pumps.Paper HOLA-10