Subsea7 secures Who Dat East Deepwater contract from LLOG Exploration
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Subsea7 has secured a new offshore contract from LLOG Exploration for the Who Dat East development, adding another deepwater project to its US Gulf portfolio as operators continue to invest in developments connected to existing production infrastructure.
The contract, announced Sept. 2, covers the fabrication, transportation and installation of subsea infrastructure linking Who Dat East to the existing Who Dat floating production system. Subsea7 classifies the award as “sizeable,” putting its value between $50 million and $150 million.
Located in Mississippi Canyon Block 509, Who Dat East sits in approximately 1,300 metres of water. Subsea7’s scope includes a 29-kilometre steel catenary riser and pipe-in-pipe system, together with the installation of an umbilical and subsea controls. Project management and engineering work will begin immediately at the company’s Houston office, with offshore activity expected to start in 2028.
The timing puts Subsea7’s offshore campaign on a similar schedule to the planned start of production from Who Dat East. Harbour Energy and its partners approved the development in August, with first production targeted for the second half of 2028.
For Subsea7, the award adds to its backlog in a market where subsea engineering, construction and installation remain essential to bringing deepwater resources into production. For Harbour Energy, which acquired LLOG earlier this year, Who Dat East represents an early example of how it intends to develop the inventory acquired through its $3.2 billion entry into the US Gulf.
Who Dat East turns existing infrastructure into an advantage
The engineering involved in Who Dat East is substantial, but the development concept itself is relatively focused.
Rather than constructing a new standalone production facility, the partners plan to connect the field to the existing Who Dat floating production system. The project comprises one well, using the Who Dat East discovery well drilled in 2024, with production transported approximately 29 kilometres to the existing facility.
That model places existing infrastructure at the centre of the project’s economics.
According to information released by project partner Karoon Energy, the development also requires subsea controls and minor upgrades to the Who Dat floating production system. Once operational, oil and gas from Who Dat East will be commingled with existing production, processed through Who Dat infrastructure and transported through established routes to market.
Initial gross production is forecast at approximately 6,500 barrels per day of liquids and 50 million standard cubic feet per day of gas. Karoon, which holds a 40 percent working interest, has estimated its share of development capital at $155 million to $165 million.
The company expects the project to generate an internal rate of return of more than 20 percent under its mid-case assumptions. That estimate remains dependent on factors including regulatory approvals, contractor performance, commodity prices and execution against the planned schedule.
The joint venture structure gives LLOG, the operator, a 40 percent working interest. Karoon USA also holds 40 percent, while Westlawn Americas Offshore owns the remaining 20 percent.
For Subsea7, delivering the connection will require an established suite of deepwater capabilities. A steel catenary riser provides the connection between subsea infrastructure and a floating production facility, while the pipe-in-pipe system provides an insulated transportation route for produced fluids. Umbilicals and subsea controls provide the communications, power and hydraulic functions needed to operate equipment on the seabed.
The individual components help explain why even a one-well subsea tieback can support a contract valued in the tens of millions of dollars.
Craig Broussard, senior vice president for Subsea7 US, pointed to the contractor’s existing relationship with LLOG when announcing the award, saying the companies share a commitment to generating greater value from LLOG’s US developments.
Harbour Energy puts its $3.2 billion LLOG acquisition to work
Who Dat East also has significance beyond Subsea7’s order book.
Harbour Energy completed its $3.2 billion acquisition of LLOG in February, marking the London-listed producer’s entry into the deepwater US Gulf and establishing another core business alongside its operations in Norway, the UK, Argentina and Mexico.
The transaction gave Harbour a fully operated, predominantly oil-weighted portfolio with producing assets and an inventory of potential future drilling and development opportunities.
Production from the acquired LLOG business averaged 36,000 barrels of oil equivalent per day during 2025. Harbour expects that figure to increase to between 65,000 and 70,000 barrels of oil equivalent per day by 2028.
That growth target puts projects such as Who Dat East into sharper focus.
Harbour has repeatedly identified infrastructure-led projects as part of its investment strategy. In its 2026 half-year results, the company highlighted a pipeline of projects using or connecting to existing infrastructure, including developments in Norway as well as Who Dat East in the US.
The attraction is relatively straightforward. Existing production hubs can provide a route for bringing additional resources into production without replicating every element of the infrastructure required for a standalone development.
Who Dat East follows precisely that model.
Its hydrocarbons will flow to a production system that is already operating, while the field itself requires a comparatively concentrated subsea development. Harbour described Who Dat East as one of the high-return, infrastructure-led opportunities competing for investment across its global portfolio when the project received final investment approval.
It also adds another development to a US business that Harbour is positioning for significant growth.
The acquisition of LLOG brought the company interests in the Who Dat and Buckskin hubs as well as Leon-Castile. Harbour said Leon-Castile started production in October 2025, while its strategy for the wider portfolio includes infill drilling, subsea developments and additional opportunities around established infrastructure.
In that context, Who Dat East is both a discrete project and part of a broader investment thesis.
Subsea tiebacks underpin the next phase of US Gulf investment
The Who Dat East award also illustrates the role contractors such as Subsea7 play as operators seek to turn discovered resources into producing assets.
The company is not entering the relationship with LLOG for the first time. Subsea7 has described the relationship as longstanding, and Who Dat East follows other recent work in the region.
In December 2025, Subsea7 announced a contract from LLOG for the Buckskin South Expansion project. That development includes the installation of subsea equipment and flowlines, with offshore activity scheduled across 2026 and 2027.
Who Dat East extends that sequence into 2028.
The significance for the subsea supply chain is not simply the number of wells involved. Deepwater tiebacks still require sophisticated engineering, specialist vessels, fabrication capacity, subsea equipment and detailed integration with existing offshore facilities.
They can also allow operators to develop discoveries around existing hubs in stages.
For Harbour, that characteristic fits its stated focus on high-return and short-cycle investments. Its May trading update highlighted infill drilling and tiebacks to infrastructure, particularly in Norway, the US and UK, among the areas it was advancing as it sought to convert resources into reserves and production.
The approach does not eliminate project risk. Deepwater developments remain exposed to complex engineering, offshore execution, commodity markets and cost pressures across the supply chain. Who Dat East itself is not expected to begin producing for another two years.
But the project already has several of the elements needed to move forward. The discovery well has been drilled, the partners have taken a final investment decision, existing processing infrastructure is available and a major subsea contractor has now been selected for the connection.
That makes 2028 the key date for both sides of the contract.
For Subsea7, it is when the engineering and project management work now beginning in Houston is expected to move offshore. For Harbour and its partners, the second half of that year is when Who Dat East is scheduled to begin contributing production.
If those schedules hold, a 29-kilometre subsea connection will turn a discovery in 1,300 metres of water into another producing component of the Who Dat system. It will also provide an early test of Harbour Energy’s strategy for the deepwater portfolio it spent $3.2 billion to acquire.
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