Key Highlights

  • Maiden Contingent Resources assigned to both Zydeco-1 oil discoveries: gross best estimate (2C) of 48,000 barrels for the Borsum Sand and 40,000 barrels for Homeseeker B, with high estimates (3C) of 60,000 and 50,000 barrels respectively
  • Homeseeker B completion being fast-tracked from the existing cased wellbore — a workover-rig operation, not a new drill program — with the nearest offset well (MacCabees B-1, approximately 300 feet away) having tested the same sand at 75 barrels of oil per day
  • Borsum Sand provides a second shallow completion option at approximately 3,400 feet with 12 feet of net pay at 32% porosity, accessible from the same wellbore without additional drilling
  • The primary Tweedel gas target remains intact and undrilled at approximately 380 feet below the casing shoe, with MacCabees-1 having flowed 3 MMscf/d from the Upper Tweedel at this location in 1950

Gulf Stream Energy Limited (ASX:GSE) has moved with notable speed since announcing its Zydeco-1 oil discoveries. Within ten days of running the wireline logs on the sidetrack, the company's external evaluator had completed a draft contingent resource assessment for both discovered sands and the operating team had prepared a completion AFE for the Homeseeker B zone. The result is a defined pathway to first oil from a wellbore that was originally drilled to test a gas target.

The Zydeco-1 sidetrack intersected two oil-bearing sands on the way to its primary Tweedel gas objective. The shallower Borsum Sand sits at approximately 3,364 feet total vertical depth with 12 feet of net pay and average porosity of 32% — a high-quality reservoir at a depth where completion engineering is straightforward. Homeseeker B, a primary objective of the sidetrack, was intersected at approximately 8,935 feet TVD with 5 feet of net pay at 24% average porosity. Both sands sit behind cemented 7-inch casing that has already been run and can be perforated and tested without returning to the drill floor.

Resources Anchored by Nearby Production History

The contingent resource assessments prepared by external evaluator Jenni Kessler are informed by the production history of nearby wells rather than flow data from Zydeco-1 itself — because no formation pressure data, fluid samples or flow tests from the sidetrack were available at the time of assessment. For the Borsum Sand, the key analogue is the F.N. Hayes 008 well, which produced from the same sand for almost 40 years. For Homeseeker B, MacCabees B-1 — approximately 300 feet from the sidetrack — tested the same sand at 75 barrels of oil per day, providing a direct offset validation for Gulf Stream's discovery.

On a gross basis, best estimate (2C) resources are 48,000 barrels for the Borsum Sand and 40,000 barrels for Homeseeker B. Applying the 30% Royalty burden, the net 2C estimates are 33,600 barrels and 28,000 barrels respectively. High estimates (3C) reach 60,000 gross barrels for the Borsum Sand and 50,000 gross barrels for Homeseeker B. These are contingent resources, not reserves, and no combined total has been reported. A 60% chance of development has been assessed but not applied to the resource figures.

Homeseeker B: The Immediate Focus

Managing Director Joseph Graham has described Homeseeker B as the immediate prize. The completion design and AFE have been prepared and the 7-inch casing is already cemented across the zone. The planned operation is a workover-rig intervention on the existing wellbore — substantially less capital-intensive than drilling a new well — designed to perforate, flow test and obtain fluid samples. The flow test will be the critical step in converting the contingent resource toward reserves.

Gulf Stream has been explicit that flow testing and fluid sampling are required to confirm producibility and that no reserves have been booked. Any decision to proceed to production will be guided by the flow test results, completion requirements and economics.

Tweedel Gas Target Preserved

Beyond the two oil completions, the primary Tweedel gas target remains accessible and undrilled. The casing shoe is approximately 380 feet above the Tweedel objective, preserving the option to deepen the wellbore at a future date. Historical precedent at the location includes MacCabees-1, which flowed 3 million standard cubic feet per day from the Upper Tweedel in 1950.

Sector Context

ASX-listed oil and gas companies with Gulf Coast Assets operate in a Jurisdiction with deep production infrastructure, established service industries and a long record of small-field commercialisation. The Gulf Coast's Miocene-age sands have supported production from hundreds of small fields and the analogous production data available to Gulf Stream's evaluator is a function of that mature Basin environment. The company's strategy of building near-term, low-cost optionality on existing wellbores is consistent with the financial constraints typical of small-cap energy companies.

Risks

The contingent resources carry a 60% chance of development and no reserves have been booked. Flow testing may not confirm producibility at commercial rates. The Borsum Sand and Homeseeker B are small-volume discoveries by industry standards, and commercialisation Economics will be sensitive to oil price and operating costs. Regulatory approvals and workover scheduling will also affect the timeline to first oil.

What to Watch Next

The completion AFE approval and commencement of the Homeseeker B workover operation are the key near-term milestones. Results from the flow test will determine whether Homeseeker B is producible and at what rate. Any decision to complete the Borsum Sand as a second zone from the same wellbore, or to pursue the Tweedel gas target, will follow from those results.