Independent energy consultant and reservoir engineer Les Anthony said more than 180 million barrels of oil remain recoverable from ExxonMobil’s Liza 1 project offshore Guyana, even as production from the country’s first oil development shows signs of decline after starting up in December 2019.
Anthony, chief executive of U.S.-based Teyshas Energy, shared in a LinkedIn post last week that Liza 1 has produced about 265 million barrels of oil since starting output in December 2019, based on publicly available data from Guyana’s Ministry of Natural Resources. He estimated remaining recoverable volumes at around 182 million barrels, based on public statements from Exxon that the project will target roughly 450 million barrels of oil production.
Using government-published production figures, Anthony said output from the Liza Destiny floating production, storage and offloading (FPSO) vessel began a “clear decline” in December 2024, following several years of variable production and incremental capacity increases that lifted output capacity from about 130,000 barrels per day (b/d) to as much as 165,000 b/d.
Liza 1 production trending back to nameplate levels | OilNOW
“The onset of decline in a producing oil field may be the result of several factors, including a loss of reservoir energy, or the limitation of the facility to handle the associated gas or water which is being produced with the oil,” Les explained.
He said the onset of decline could reflect natural reservoir depletion or facility constraints, such as limits on handling produced gas or water, but stressed that determining the cause would require well-by-well production, injection and pressure data that are not publicly available.
Anthony noted that Guyana’s published data covers only aggregate FPSO oil output, limiting the ability of outside analysts to forecast long-term reservoir performance with precision.
Liza 1, operated by ExxonMobil with partners Hess and CNOOC in the Stabroek Block, was Guyana’s first commercial oil development and has now been overtaken in output by newer projects, including Liza 2, Payara and Yellowtail.
Anthony also said the field may retain a smaller volume of recoverable gas at abandonment, potentially less than 200 billion cubic feet, which could be considered for future monetisation as part of the broader Stabroek development, depending on commercial and infrastructure conditions.
Gas from the Liza 1 project is expected to flow to shore next year as the completion of the Gas-to-Energy project development draws near. Liza 1 and 2 are expected to deliver gas at a rate of 50 million cubic feet per day (b/d).
