The Exxon Mobil Corp.-led consortium searching for oil and gas to produce offshore Guyana have struck net pay again, growing estimated discovered recoverable resources beyond the 9 billion barrels of oil equivalent or so on the Stabroek Block.

The company said June 9 the Longtail-3 well encountered 230 ft of net pay, which included newly identified, high quality hydrocarbon-bearing reservoirs beneath the original Longtail-1 well. The size of the discovery’s estimated oil and gas reserves was not specified.

The Koebi-1 exploration well on the same block, however, was deemed non-commercial, Exxon said.

Longtail-3 was drilled by the Stena DrillMax drillship in more than 6,100 ft of water about 2 miles south of the Longtail-1 well, the 2018 discovery that hit oil.

The latest find brings the discovery count on the block to 20 for Exxon and partners Hess Corp. and the China National Offshore Oil Co. Ltd., further highlighting the value the hydrocarbon-lush 6.6 million-acre Stabroek Block has for increasing future output. It follows news in April of the consortium’s oil find at the Uaru-2 well.

“Longtail-3, combined with our recent discovery at Uaru-2, has the potential to increase our resource estimate within the Stabroek block, demonstrating further growth of this world-class resource and our high-potential development opportunities offshore Guyana,” Mike Cousins, senior vice president of exploration and new ventures at ExxonMobil, said in a statement. “We will continue to leverage our core competitive advantages in our ongoing exploration campaign, delivering substantial value to the Guyanese people, our partners and shareholders.”

In a separate statement, Hess CEO John Hess said the discovery combined with the others “underpin future development opportunities for the Stabroek Block.”

The companies also said June 9 the Mako-2 appraisal well confirmed the quality, thickness and areal extent of the reservoir. The original Mako discovery was announced in December 2019 as the consortium’s 15th oil discovery on the block.

“When integrated with the previously announced discovery at Uaru-2, the data supports a potential fifth floating production storage and offloading vessel (FPSO) in the area east of the Liza complex,” they said.

During first-quarter 2021, Exxon deployed the fifth and sixth drillships offshore Guyana as it continues exploration, appraisal and development drilling as part of a 15-well campaign on the block. The company said June 9 the DrillMax will move to the Whiptail-1, and the Noble Sam Croft will support development drilling for Liza Phase 2.

Speaking during the Credit Suisse Energy Summit in March, Hess COO Greg Hill described Whiptail as “a very large structure.” During the summit, he explained that the partners’ objectives this year included filling out the mosaic of potential in the upper Campanian reservoirs of the block, getting some penetrations in the deeper Santonian to better understand that area and appraising additional discoveries to help underpin future developments beyond Yellowtail.

Source: Hess Corp./Credit Suisse Energy Summit presentation (March 2021)

In a statement, the government of Guyana welcomed news of the latest discovery.

The government of Guyana anticipates that this new development will further increase the potentials for more floating production storage and offloading vessels (FPSO),” it said. “Additionally, this will increase the estimated recoverable resource given by the operator, Esso Exploration and Production Guyana Limited (EEPGL). As such, the ministry and the petroleum sector regulatory agencies will continue to work with other operators to expedite their drill program as we seek to expand the sector.”