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. 

Takutu Basin,

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). 

GENERAL INFORMATION

Petroleum includes all naturally occurring carbonaceous liquids such as crude oil, natural gas, and natural asphalts.  Petroleum is very common in small amounts and is widely distributed, however, it is rare that large accumulations that contain commercially important quantities are found.

Commercial accumulations of petroleum are dependent on technical, economic and political factors that influence whether an accumulation is worth developing in the existing circumstances.  Profitability is based on the following factors: 

  • Depth,
  • Geographic position,
  • Properties and amount of oil or gas,
  • Operations cost including drilling, production, and refining,
  • Price,
  • Fiscal regime, and
  • Political stability.

Petroleum Reservoir – A reservoir is a formation of mostly solid rock with tiny openings, or pores, which can hold fluids.  Reservoir rock usually contains hydrocarbons as well as water (mainly salt water).  Usually, these fluids are layered; gas (the lightest) on top, oil in the middle, and water (the heaviest) at the bottom.  It is preferred that reservoirs contain all three fluids; oil and gas are valuable minerals, and the gas and water often providing the driving force for oil to reach the surface.  This makes pumping unnecessary.

To accumulate a commercially valuable petroleum deposit, a reservoir must have the necessary configuration:

  • Porosity of 10% or more pore space,
  • Permeability of 10% or moreso that pores must be connected so oil, gas, and water can flow through it by moving from one pore space to another, and
  • The right seal and trap mechanisms that keep the petroleum from escaping.

Geology is the science that deals with the structure and history of the earth and its life forms, especially as recorded in the rocks.  This science is essential to the petroleum industry, for it is used to predict where oil accumulations may occur.  Petroleum geology involves those aspects of geology associated in the discovery and production of petroleum.  Petroleum geology involves all aspects of geology and other related disciplines such as geophysics, paleontology, geochemistry, and other engineering fields.

The first principle is that the present is key to the past; i.e., the processes acting on the earth today are the same as those that operated in the past.

Some of the Largest Oil Fields (based on future recoverable reserves) are:

  • Ghawar, Saudi Arabia                                          75 billion bbl
  • Burgan, Kuwait                                                    66 billion bbl
  • Bolivar Coastal Fields, Venezuela                         30 billion bbl
  • Safaniya-Khafji, Saudi Arabia/Neutral Zone          25 billion bbl

 

One of the Largest Gas Fields

  • Urengoi, Western Siberia           285Tcf (dry gas)

 

Petroleum Production Rates

Varies from 1 bbl/day (stripper wells) to more than 10,000 bbl/day.  Many stripper wells (they are so called because they produce from 1 to at least 20 bbl/d) are found in Oklahoma, Texas, Arkansas, and Louisiana, USA.      

 

Well Depths:

Well depths range from a few feet to 40,000 feet.  The deepest producing oil well is 22,000 feet in Southern Louisiana, and for the deepest producing gas well it is 26,500 feet in Oklahoma.  Most production is in the range of 2,000-10,000.