Granite as Oil Reservoir
Monday, July 11, 2011 11:21:26 AM
More than twenty reservoirs have been found in basement rocks all over the world. A good example is from the Bach Ho (White Tiger) Field in Vietnam. In Vietnam, basement reservoirs are major reservoirs, which are providing something like 80-90% of the production rate.
In the Utsira High in the Norwegian part of the North Sea plenty of oil has now been found in a 439 million year old fractured and weathered “rotten” granite with good reservoir properties (average porosity 9% with a maximum in some zones of up to 20%) . A short test production produced 650 barrels of oil per day.
The porosity is due to weathering of the rock when it was exposed to air and water in the Triassic and Jurassic periods so that the feldspars were dissolved. Please bear in mind that the Triassic and Jurassic periods were hot and humid in this part of the world when Baltica and the Fennoscandinavian shield were situated much closer to the equator.
On the British shelf Hurricane Exploration is also looking for oil in the basement with a few finds.