The largest known hydrocarbon deposit in the world, the Orinoco Belt in Venezuela, contains oil with a gravity ranging from 9 to 14degrees API. The Hamaca project encompasses more than 400 square miles of the Orinoco Belt and is believed to contain more than 30 billion barrels of extra-heavy oil (9degrees API). Production of the project started in November 2001 and the target is to produce some 30,000 m(3) (190,000 barrels) a day over a life span of more than 35 years. This study found that using propane as a steam additive can accelerate oil production and improve the effect of steam injectivity in the Hamaca field. In our laboratory study, steam-propane injection accelerated the start of oil production by 21% compared to that with pure steam injection. In the field, this could translate into significant gains in discounted revenues and a reduction in steam injection costs. Second, steam injectivity with propane as an additive was up to three times higher than that for pure steam injection. Third, accelerated oil production and increased injectivity were practically the same for all of the runs using propane as a steam additive (irrespective of the propane-steam mass ratios). Propane appears to be a viable steam additive at propane-steam mass ratios as low as 2.5:100.