Use of Natural Gas as a Driving Force in a Diluent-Gas Artificial-Lift System Applied to Heavy Oils

Abstract

Abstract The diluent-gas method is an artificial lift system for heavy oils (as low as 8.5 °API), where a light crude is used as diluent and it is injected into the well along with natural gas in order to reduce the viscosity of the crude oil therefore increase oil production. This method is unique in the world and has been long used in Venezuela. Due to high maintenance costs, 20,000 US$ annually, incurred in replacing and repair diluent pumps (reciprocating pumps), which are used to inject at 900-1,000 psig the diluent (28-35°API) into the well, those pumps are considered as a critical system, basically, because of high operational pressures and oil production deferred, which is estimated in 2,500 barrels per year. This project was based on analyzing a novel way to pump the Diluent and Gas down the well. The equipment designed is denominated Gas Displacement Pump and utilize the same gas lift (900 – 1,000 psig) as a driving force to inject the Diluent into the well. The system is made up of a vessel, a group of valves, pipes, level control systems, etc. This novel design will allow minimizing; deferred oil production, environmental damage and maintenance costs, OPEX is reduced considerably (85%), as the Gas Displacement Pump will not have moving parts thus maintenance expenses would be low, generating this significant savings to the company. Finally, it was demonstrated that there is no slug flow formation using this new system and that the flow regime governing the system is stratified.