Gulf of Mexico: Further hydrocarbon upside potential on the horizon as initial drilling ops show promise

While the intermediate logging of an exploration/appraisal well in the U.S. Gulf of Mexico is said to have confirmed high-quality, hydrocarbon-bearing sands in upper target sections, the U.S.-headquartered oil and gas exploration and production player, LLOG Exploration, still has several deeper targets to spud.

Following LLOG’s approval of the drilling operations at the Who Dat East appraisal/exploration well in the Gulf of Mexico, the MC 509-1 well was spudded at the end of April 2024, with Noble Corporation’s Noble Valiant drillship. The Who Dat East joint venture (JV) participants are LLOG (operator, 40%), Karoon (40%), and Westlawn (20%). 

According to Karoon, the Who Dat East exploration/appraisal well has reached a measured depth (MD) of 6,614 meters in the 12-¼” hole section, with intermediate wireline logging completed before setting 9-⅞” casing. The well is now expected to drill ahead in an 8-½” hole to a planned final total depth (TD) of 7,900 meters.

The borehole angle through the 12-¼” hole section is around 45 degrees and the logging while drilling (LWD) and wireline logging data indicate that multiple hydrocarbon-bearing sandstones have been encountered within the targeted Middle Miocene turbidite sequences.

Karoon points out that the interpretation of this data indicates a hydrocarbon-bearing aggregate total net pay thickness of 44 meters MD within the targeted intervals, with 31 meters MD within two discrete reservoir units.

In addition, there are indications of net pay porosities average of 25% and correspondingly good permeabilities between 300-meter depth to greater than 1,000-meter depth. Karoon underlines that a gas condensate hydrocarbon fluid type has been interpreted at the well.

Dr. Julian Fowles, Karoon’s Chief Executive Officer and Managing Director, commented: “Preliminary interpretation of the well data from the Who Dat East exploration/appraisal well is positive. The early results indicate potential for a continuous hydrocarbon phase in a number of high quality sands correlated to the nearby MC-509 Exxon #1 exploration well.”

Moreover, wireline logging data, reservoir fluid samples, and other geoscience data will be subject to laboratory analyses and further studies to gauge the resource potential of the hydrocarbon zones encountered to date. Moving forward, the plan is to complete running 9-⅞” casing before drilling to the planned total depth of around 7,900 meters MD to test the remaining targets.

The Who Dat East asset is estimated to contain 17 MMboe of gross unrisked 2C contingent resources and 35 MMboe of gross unrisked 2U prospective resources, with an aggregate geological probability of success estimated to be 62%.

Fowles highlighted: “Once the remaining targets have been drilled and final TD logging completed, we shall be in a better position to evaluate any potential impact on hydrocarbon volumetrics at Who Dat East, with a view to determining the commerciality of a potential development.

“Furthermore, this early success at Who Dat East supports our belief that there is exploration upside potential that can be unlocked surrounding Who Dat. Once drilling is complete the well will be suspended as a potential future producer, pending the results of further analysis.”

The Who Dat conventional deepwater oil and gas development, which came on stream in 2011, is located in 800 meters of water offshore Louisiana within federal waters of the U.S. Gulf of Mexico. The asset produces around 60% oil and 40% gas from nine wells processed through the Who Dat floating production system (FPS) and transported to markets through common carrier pipelines.

LLOG will start drilling the MC 545-1 exploration well in the Who Dat South prospect toward the end of Q2 2024, using Seadrill’s West Neptune drillship to test two targets in the Miocene section, with the shallower target being similar to the reservoir in the G-1 well in Who Dat.