Gulf Stream maps a faster route to first oil at Zydeco

Two Zydeco oil zones receive maiden resource estimates

Gulf Stream Energy Limited (ASX:GSE) has moved its Zydeco-1 oil discoveries beyond log interpretation, assigning a gross best estimate of 48,000 barrels to the Borsum Sand and 40,000 barrels to Homeseeker B. The estimates are Contingent Resources, not reserves, and remain classified as Development Unclarified.

The company’s external evaluator put the low-to-high range at 36,000 to 60,000 barrels for Borsum and 30,000 to 50,000 barrels for Homeseeker B. After the stated 30% royalty burden, the corresponding net best estimates are 33,600 and 28,000 barrels. The figures are deterministic and have not been adjusted for the reported 60% chance of development.

Homeseeker B is the first test of commercial potential

Gulf Stream’s immediate plan is to complete and flow-test Homeseeker B using a workover rig on the existing wellbore. The 7-inch casing is already cemented across the zone and a completion AFE has been prepared, meaning the proposed operation does not require a new drilling program.

That creates a relatively direct technical test, but not a guaranteed production result. The well has not yet provided formation pressure data, fluid samples, flow-test results or production data. The evaluator instead relied on logs and nearby wells, including MacCabees B-1, about 300 feet away, which tested the same Homeseeker B sand at 75 barrels of oil per day and 25 barrels of water per day. Those offset results are explicitly not forecasts for Zydeco-1. The resource announcement follows the Zydeco oil indications, which had initially been based on wireline logs without flow testing.

Borsum provides a second completion option

The shallower Borsum Sand sits at about 3,364 feet true vertical depth and contains 12 feet of interpreted net pay with average porosity of 32%. Gulf Stream says it can be completed later from the same wellbore, offering a second production zone if engineering, flow-test results and economics support that decision.

Nearby evidence is also encouraging but limited. ABM 001 tested 107 barrels of oil per day, while F.N. Hayes 008 tested 66 barrels per day and produced from the Borsum Sand until 1987. The company has not approved a development plan or made a completion decision for either zone.

Tweedel gas target remains untouched

The oil discoveries were not the original reason for drilling Zydeco-1. The primary target, the Upper Tweedel, remains approximately 380 feet below the existing casing shoe. Gulf Stream says a 1950 well at the location kicked and flowed at 3 million standard cubic feet of gas per day from the formation, but the current Tweedel target has not been drilled or tested.

A deepening AFE has been prepared, with about 620 feet of new hole required below the casing shoe. Any move toward that programme remains subject to engineering review, funding and approvals. For now, the company’s next meaningful data point is more immediate: whether Homeseeker B can produce oil at commercially relevant rates and with manageable water production.