Exploration of The Bahamas region by multinational oil companies occurred continuously from the mid 1940s until 1988. Peak industry activity, which resulted in exploratory well tests, occurred in approximately twelve year intervals.
Early exploratory activities (1946 to 1947) included small local gravity and magnetic surveys that were performed by contract for eight oil companies. Some of these companies included Gulf Oil, Standard Oil (Chevron), Superior Oil and Shell. This early activity resulted in the drilling of the first Bahamian well-the Andros Island #1 well on Andros Island (target depth (“T.D.”) 14583 feet). The well was plugged and abandoned with no significant hydrocarbon shows reported.
From 1948 to 1955, the region experienced only limited exploratory activity. However, this limited activity (by Gulf in 1948 and 1950) did include the first experimental underwater seismic and gravity surveys. The Gulf 826-Y well was drilled west of Key West, Florida. It is the only well to successfully flow oil. This well flowed 18 barrels of 22-24API gravity crude oil from an interval of anhydrite and carbonate lithologies below 10,000ft.
In 1956, Bahamas California Co. (Chevron) and Bahamas Exploration Co. (Gulf) performed a detailed seismic and engineering survey of the Cay Sal Bank area. The second exploratory test in The Bahamas, the Cay Sal #1 (T.D. 18906 feet), was a joint test by the two companies in 1959. This well encountered common “live oil shows” from 12682 feet to T.D., but with no commercial quantities of hydrocarbons tested.
From 1959 to 1968, active lease holding occurred where up to eight companies held the entire Bahamas region under concession. Gulf and Chevron led the majority of the exploratory activity by completing many experimental marine seismic programs (including the use of dynamite as an energy source). The lack of success in the acquisition of this primitive interpretive quality marine seismic data in the bank regions did not encourage well tests during this period.
In 1970, Gulf, Chevron and Mobil drilled a joint test, the Long Island #1 well (T.D. 17,577 feet). This well was plugged and abandoned after having encountered only minor live hydrocarbon shows in the 15,900 feet depth interval. The rig was then moved to the Great Isaac Bank where the Great Isaac #1 well was drilled by Chevron to a total depth of 17,847 feet. This well did encounter minor live hydrocarbon shows in the 16,900 feet to 17,700 feet depth interval with an overpressured reservoir containing gassy water at 17,436 to 17,495 feet depth interval. Drilling fluids were 9.2ppg drilling into the overpressure pressured reservoir and were eventually increased to 16.0ppg before drilling on to TD. However, no commercial quantities of hydrocarbons were reported on tests.
From 1970 to 1983, industry exploratory activity involved primarily new digitally-based seismic, gravity and magnetic surveys. Academic institutions and the Deep Sea Drilling Project were actively involved in attempting to understand the nature of the carbonate bank of The Bahamas through the acquisition of subsea and subsurface samples as well as new seismic and potential field data.
By early 1980s, Esso, Arco, Getty, Natomas and Breoco had attempted to obtain licence positions over major portions of The Bahamas. Final licence positions did change hands and by 1984 the companies that were strongly interested included Esso, Amoco, Tenneco, Texaco, Arco, Breoco and Shell. By 1985, industry exploratory activity included the completion of then state of the art seismic surveys, gravity and magnetic surveys, surface and subsea geochemical surveys, and geotechnical site surveys. Tenneco Oil Company was the leader in employing the greatest amount and variety of exploratory surveys. During this time interval the international scientific Ocean Drilling Program drilled a series of tests to gather shallow subsurface data.
Map showing previous Exploration Licences held
By late 1986, Tenneco had spudded the Doubloon Saxon #1 well, the deepest test drilled in The Bahamas. The well, drilled to 21,740 feet, did not report commercial quantities of hydrocarbons but did have live oil shows over a thick interval. Following this exploratory test, licence interests remained with Tenneco and Shell (Shell acquired Arco’s position). Additional post-drilling new experimental seismic surveys were performed by Tenneco and Shell during 1986 and 1987.
All licences expired in 1988 due to a work commitment for 1989 of $250m, and low oil prices.
Location of Well Log Section
Table showing Petroleum Exploration Wells, Onshore Bahamas and Bahamain Waters
Overall, the well results suggest the presence of active petroleum systems, based on the presence, especially in the pre-mid Cretaceous Unconformity sections, of oil shows of varying quality, abundant reservoirs and seals, indications of source rocks, and hydrocarbon saturations from log interpretation.
