Guyana is divided into two Petroleum Basins named Guyana and Takutu, respectively. The Guyana Basin is further divided into two basins, Onshore and Offshore. Herein is a synopsis of the Basins.
Onshore Guyana Basin
The deepest part of the southern “boundary” is some 150 miles from the Guyanese Coastline. NABI Oil And Gas, Inc. and ON ENERGY Inc. companies have concessions within this part of the Basin.
Within the Onshore Guyana Basin, there was a chance of these blocks being subjected to competitive bidding, however this does not take away any one’s prerogative to apply for concessions within this area. There were 13 wells drilled within this part of the Basin from 1916 to present day. Only Rose Hall-1 drilled in 1941 and Drill-1 in 1967 had oil shows. The eastern part of the Onshore Guyana Basin has the largest thickness of sediments reaching some 2,500 m. It should also be noted that the gas found on the coast is nearly all biogenic, with a very small area yielding thermogenic gas.
Offshore Guyana Basin
REPSOL, ANADARKO, ESSO/HESS/NEXEN, Mid-Atlantic Oil and Gas, Inc., RATIO Energy/Guyana Ltd and CGX Resources Inc. have petroleum concessions in this part of the basin. Presently, a number of companies are negotiating for concessions in the offshore Guyana Area.
On the aspect of Offshore Guyana Basin, from the nearshore to around 80 miles to the north, the seabed is generally on the continental shelf then it moves to the slope and as one gets further it reaches the deep-water area. From the northwest (where the Anadarko concession is) to the Northeastern area depths can be from 1,000 feet to more than 10,000 feet. This area is known as the “ultra-deep waters”. In May 2015, ESSO made a significant discovery of petroleum while drilling in its Stabroek Block.
Guyana has never had a commercial petroleum discovery, although there are a number of wells that had oil and gas shows both onshore and offshore. Prior to the ESSO discovery, our “best” well has been Karanambo-1 well drilled by Home Oil in the Takutu Basin in 1982.
Located in the southwestern area of Guyana lies the Karanambo-1 well, which was drilled in 1982 by Home Oil Company. This was the best prospect drilled within this Basin. Located in southwestern Guyana a small amount of light crude was accrued. Tests conducted on samples from Karanambo-1 found that the oil is of good quality (420API) and is of a “sweet” variety, that is, it contains less than 0.5% hydrogen sulphide. However, its geological characteristics are mainly naturally fractured reservoirs, thus proving more difficult to find commercial petroleum than regular reservoirs. The other wells drilled in the Takutu are Lethem-1 (1980), Turantsink-1 (1992) and Apoteri K2 well (2011).