A New Analytical Model for the Prediction of Fluid Production and Gas Consumption of Gas Chamber Pumps
Ali Hernandez, SPE, Sergio Caicedo, SPE, Luisana Marcano, PDVSA INTEVEP., Juan Brown, PDVSA EP
Recent experimental studies on intermittent gas lift have shown that the lift efficiency of this method decreases drastically as the viscosity of the fluid to be lifted increases. As the viscosity increases more gas is needed to keep the fallback losses at a minimum. One way to get around this problem and eliminate fallback losses is to implement the use of Gas Chamber Pumps (GCP’s).
GCP’s are highly appropriate for shallow wells producing heavy oil in places where high-pressure injection gas is available. That is the case of some wells in Lake Maracaibo and in some places in the eastern oil fields in Venezuela that are currently producing oil of 14 to 23° API from reservoirs located at depths between 2000 and 3500 ft.
A variety of different GCP configurations can be found in the literature, from highly complex and compact units to simple types of completion that can be implemented with minor changes of current gas lift completions. The advent of simple and highly reliable programmable surface controllers is making it possible to simplify subsurface completion. The simplicity of these new completions implies a new and economical way of implementing GCP’s where they are appropriate.
A description of how different GCP’s work and the most popular configurations are given in this paper. It is also explained in detail a new and simple engineering procedure to estimate the liquid production and gas consumption of a well producing with a GCP. This procedure takes into account the inflow capability of the well and couples this capability with the pressure losses across the different parts of the completion and the flow and pressure capacity of the gas lift system.