Primary recovery relies on the naturally high differential pressure between reservoirs and the surface. While underground oil reserves are already higher in pressure than wellbores, this difference is maximised by drive mechanisms, such as water drive, where water is pumped into the well, displacing the hydrocarbons, increasing their pressure, and forcing them up the wellbore.
Another common drive mechanism is gas drive, used when oil reserves contain dissolved and free gas. This expands as the reservoir pressure lowers, forcing the hydrocarbons up to the surface. Often, this rapid expansion of energy creates oil geysers.
Key fact: The ultimate recovery ranges are 5-30% OOIP for gas drive mechanisms and 35-75% OOIP for water drive mechanisms
When the pressure is no longer high enough for oil to flow to the surface, pump jacks are used. Sometimes referred to as rod pumps, these are artificial life systems that pressurise the well downhole and pump hydrocarbons out.
Benefits
Increases flow rate of hydrocarbons
Low capital investment
Improves productivity
