Geologist Publishes Update on Natural Hydrogen Exploration Offshore Southern Cuba

      Petroleum geologist Marcello Rebora recently published an article in GeoExPro about natural hydrogen exploration offshore Southern Cuba. He first notes that it is generally accepted that most natural hydrogen is generated by ophiolites of the mantle reacting with water. Cuba has both surface ophiolites and ophiolites at depth.

“This author believes that the sprinkling of islets (cayos) and larger shoals in the West Cuba Caribbean, a paradise for lobster and fish lovers, are generated by gas and fluids seeping to the surface as mud volcanoes, hydrate mounds and seep-related reefs, gradually encouraging growths on the sea bed.”

     Ophiolites are sections of oceanic crust and mantle that have been uplifted, often overtopping existing oceanic or continental crust. Metamorphic rocks known as serpentinites are associated with ophiolites as well as considered to be a major source of mantle-derived natural hydrogen seeps. 

     He notes that on good quality seismic data, gas chimneys and hydrothermal vents can be identified. He also notes that it is not uncommon to find “hand-size disks of plastic bitumen,” likely expelled from far below by hydrothermal waters and gas.

     Rebora mentions two wells drilled in the area, one back in the 1950s, Stanolind well Tortuga Shoal (TS-1), which was drilled to 9,700 ft. That well encountered reef fragments in a basinal setting and a gas kick at 9300 ft.

     The other well was drilled in the 90s by Swedish, Italian, Spanish, and Canadian companies. This was the Ana Maria- AM-1, which:

“… tested 20 m of overpressured gas in a porous Cretaceous limestone. The basinal Cretaceous section contained fragments of rudistic reefs. A side-track (AM-2) drilled into 190 meters of an ophiolite complex. The Cretaceous sediments contained crystals of sphalerite, saddle dolomites, and uranium believed to be associated with hydrothermal waters. Neither of the two wells found obvious source rocks.”

     Both wells, as shown below, were not drilled to test the reefs that were interpreted later.

     Another well was planned in the 2000s to test the Bajo Corales reef, about 800 meters updip from the gas show tested in the 90s. The reef, like several in the area, has a direct hydrocarbon indicator (DHI) known as a flat spot. DHI’s have been very successful in predicting commercial discoveries. Reefs are also known to have excellent porosity, with a massive 30% porosity possible.  

“These wells were practically blind stratigraphic holes, as seismic control was skimpy and quality was poor below the Tertiary; AM-1 found 33 degree dips in the Cretaceous section. At that time, the Upper Cretaceous reefs could not be recognised, let alone mapped. New, good-quality seismic of the late nineties revealed a number of these reefs, many with DHIs such as flat spots.”

     Below is a two-way-time structure map based on seismic, of the top of the Cretaceous, which shows the five large reef complexes along with several other smaller ones to the north and east. He notes that:

“…the total potential gas reserves of these five reef bodies is calculated to be 18 trillion CF of mainly hydrogen and methane.”

     This is certainly an interesting prospect area. However, the ongoing political situation in Cuba may be a factor in its not being drilled. Other issues are uncertainty about source rocks for the natural gas, although the source of the hydrogen is the mantle. He does not give any information about the hydrogen percentages encountered in the two old wells.  

   

References:

 

Natural hydrogen exploration offshore Southern Cuba: Will Cuba be the first country to produce commercial quantities of hydrogen? Marcello Rebora. GeoExPro. December 5, 2025. Natural hydrogen exploration offshore Southern Cuba - GeoExpro