ExxonMobil Corp. (NYSE: XOM) and partners have added a 10th discovery to its blossoming exploration success story offshore Guyana, where discovered recoverable resource estimates have now surpassed 5 billion barrels of oil equivalent (Bboe).

The Irving, Texas-headquartered company said Dec. 3 the Pluma-1 well, which was drilled by the Noble Tom Madden drillship, hit about 37 m (121 ft) of high-quality hydrocarbon-bearing sandstone reservoir. The well is located about 27 km (17 miles) south of the Turbot-1 well.

Drilled to a depth of 5,013 m (16,447 ft) in a 1,018 m (3,340 ft) of water, the well-targeted Upper Cretaceous reservoirs.

“The discovery of a resource base of more than 5 billion oil-equivalent barrels in less than four years is a testament of our technical expertise and rigorous evaluation and pursuit of high-potential, high-risk opportunities in this frontier area,” Neil Chapman, ExxonMobil senior vice president, said in the release. “We will continue to apply what we’ve learned to identify additional exploration prospects and potential future discoveries that will deliver significant value to Guyanese people, our partners and shareholders.”

The drillship is set to drill the Tilapia-1 prospect next. Tilapia is located about 5.5 km (3.4 miles) west of the Longtail-1 well, ExxonMobil said.

The Pluma-1 discovery followed news in August of the Hammerhead-1 discovery, which opened a new play concept for potential development.

So far, ExxonMobil has announced five discoveries in the Stabroek Block this year with the latest bringing the total count to 10. Others include Liza, Liza Deep, Payara, Snoek, Turbot, Ranger, Pacora, Longtail and Hammerhead, proving the hydrocarbon-prolific nature of the 26,800-sq-km block.

“Our ongoing work will evaluate development options in the southeastern portion of the block, potentially combining Pluma with prior Turbot and Longtail discoveries into a major new development area,” said Steve Greenlee, president of ExxonMobil Exploration Co.

The Stabroek Block is operated by ExxonMobil affiliate Esso Exploration and Production Guyana Ltd., which holds a 45% interest in the block. Partners are Hess Guyana Exploration Ltd. (30%) and CNOOC Nexen Petroleum Guyana Ltd. (25%).

“Guyana is a truly world class investment opportunity with multi billion barrels of additional exploration potential,” John Hess, CEO of Hess Corp. (NYSE: HES), said in a statement. “The growing resource base on the Stabroek Block further underpins the potential for at least five FPSOs producing more than 750,000 barrels of oil per day by 2025.”

The latest find was made as work progresses on development of Liza Phase 1, the play-opening discovery. Sanctioned in June 2017, Liza Phase 1 is expected to mark first oil by early 2020, producing up to 120,000 barrels per day (bbl/d) of oil from the Liza Destiny FPSO.

The larger Liza Phase 2 development will have a capacity of 220,000 bbl/d. “Pending government and regulatory approvals, Liza Phase 2 project sanction is expected in early 2019 and will use a second FPSO designed to produce up to 220,000 barrels of oil per day,” the release said.

A third development, Payara, is also on the horizon. If sanctioned, a decision for which is expected next year, production could begin in 2023. The Payara Field is located about 12 miles northwest of Liza.

The total resource base on the block, which increased from the previous estimate of more than 4 Bboe, “reinforces potential for at least five floating storage, production and offloading vessels producing more than 750,000 barrels of oil per day by 2025,” according to Hess.