Artificial Lift Methods

Most oil wells, at the early stages of their life, flow naturally to the surface. These are called flowing wells. The basic prerequisite to ensure flowing production is that the pressure at well bottom be sufficient to overcome the sum of pressure losses occurring along the flow path to the surface. When this criterion is not met, the well stops to flow naturally and dies. There are two main causes of a well's dying: either the bottomhole flowing pressure drops to a level that is no longer sufficient to overcome pressure losses in the well, or the flowing pressure losses increase above the bottomhole pressure necessary for the well to produce. The first case happens due to the removal of fluids from the underground reservoir, which entails a gradual decrease in reservoir pressure. In the second case, mechanical problems (tubing size too small, downhole restrictions, etc.) or a change in the composition of the flowing fluid (usually a decrease of gas production) tend to increase the flow resistance in the well. Surface conditions, such as separator pressure, flowline size, etc. also have a direct impact on total pressure losses and can prevent a well from flowing.

To produce wells that are already dead, or to increase the production rate from flowing wells, some kind of artificial lifting equipment is needed. Several lifting systems are available to choose from, and all work on the principle of supplying the energy needed from the surface in order to move well...