And the Persian Gulf oil states have yet to apply the new gas/fluid injection technology that could tremendously extend the life of many oilfields. Once the injection technology comes into use there, they could extract oil at current production rates for possibly 80 years or more.
You may be surprised at what is already used. Secondary and Tertiary recovery methods have been used their for many years.
For example:
Ghawar: The Arabian Granddaddy
http://www.epmag.com/ghawar-arabian-granddaddy-775846#p=4
Gas injection was introduced in 1958, according to “Hydrocarbons Technology,” and water injection began in 1964 to provide pressure support. Today water is pumped by pipeline from the Qurayyah Seawater Treatment Plant.
In 1995 Aramco conducted a 3-D seismic survey to examine the reservoir structure and fracture distribution to guide future development of the field. More recently the company began the Haradh III project, which relies on maximum-reservoir-contact wells and downhole interval control valves for flow control. Geosteering also has been used, and wells have been equipped with intelligent sensors for continuous monitoring.