Key Highlights

  • Gross unrisked 2U prospective resources at Northern Hinge are 4 Tscf of natural hydrogen, 102 Bscf of helium and 320 Bscf of petroleum gas.
  • The assessment covers 28 leads across four exploration permit application areas in South Australia.
  • Seabrook, the largest lead, holds about 761 Bscf of hydrogen and 22 Bscf of helium on a gross unrisked 2U basis.
  • An exploration drilling campaign is targeted for mid-2027, subject to permit grants, approvals, financing and readiness.

Prominence Energy Limited (ASX:PRM) has defined maiden gross unrisked 2U prospective resources of 4 Tscf of natural hydrogen, 102 Bscf of helium and 320 Bscf of petroleum gas across 28 identified leads at its Northern Hinge Project in South Australia. The company prepared the assessment, and RISC Advisory independently audited it, according to the announcement of 22 October 2026.

The estimates relate to undiscovered accumulations within four exploration permit application areas, PELA 566, 581, 752 and 753, which remain subject to grant. Prominence said the work provides a technical basis for target ranking, potential partnering and exploration drilling targeted for mid-2027.

Resource Ranges and the Seabrook Lead

The 1U, 2U and 3U cases represent low, best and high estimates, broadly corresponding to P90, P50 and P10 outcomes. Gross unrisked hydrogen is 2,821 Bscf at 1U, 4,001 Bscf at 2U and 6,210 Bscf at 3U. Helium is 71.5, 101.8 and 157.7 Bscf, and petroleum gas is 138.1, 320.0 and 821.4 Bscf. On a gross risked basis the 2U figures fall to 543.8 Bscf of hydrogen, 13.7 Bscf of helium and 53.5 Bscf of petroleum gas.

Seabrook, in PELA 753, is the largest of the 28 leads, with gross unrisked 2U resources of about 761 Bscf of hydrogen, 21.7 Bscf of helium and 363 Bscf of methane. It accounts for roughly 20% of the portfolio's gross unrisked 2U hydrogen and helium resources. Prominence interprets it as a positive flower structure associated with faulting, with vertical closure of 50 to 100 metres, areal closure of 50 to 290 km2 and possible gas chimneys at the fault terminus.

The top five 2U unrisked hydrogen and helium objectives audited by RISC are Seabrook, Rockford, Flowstone, 581_1 and 581_2. The company said regional artesian spring measurements of up to 2% helium and 74% methane should not be read as gas composition at Seabrook or any proposed well.

What the RISC Audit Covered

Leads were identified from gravity, magnetic, geological mapping and sparse seismic data. RISC reviewed lead identification, probabilistic inputs, gas composition and geological risking, accepting the methodology and inputs as reasonable for a frontier area while noting uncertainty in lead definition and the available subsurface data. The estimates are Prominence's own, and RISC did not generate a separate set.

Prominence assessed geological chance of success at 6% to 18% per lead, using source, reservoir, trap and seal factors. RISC considered elements of the risking optimistic, particularly trap and seal, and regarded charge as the highest-risk element, but accepted the overall approach as reasonable with reservations. RISC's letter does not establish a discovered accumulation. The audit is also not a commerciality assessment, reserves certification or project valuation.

The hydrogen volumes follow petroleum resource principles applied by analogy, consistent with guidance noted by RISC, and totals are by probabilistic summation of the individual leads. Hydrogen mass is converted at 2,321.98 tonnes per Bscf, which translates the 2U unrisked case to about 9.29 million tonnes.

Permits, Timeline and Partnering

Prominence is the first applicant for the Northern Hinge permit areas and has completed an Indigenous Land Use Agreement process, though the petroleum exploration licences remain subject to government approval. Activities that require tenure cannot proceed until licences are granted.

The work program lists the Eyre review and the Northern Hinge resource review as delivered. An updated drilling engineering and cost assessment and the start of a farm-out process are next in October 2026, detailed design of the 2027 program is planned for November and December 2026, and a multi-well helium and natural hydrogen drilling program is targeted for mid-2027. The company is considering farm-out and strategic partnering structures, with no certainty that an agreement will be concluded.

Northern Hinge sits alongside the Eyre assessment of September 2026, which reported 2U unrisked resources of 202.8 Bscf of hydrogen and 9.2 Bscf of helium, within a South Australian portfolio of about 64,000 km2.

Where the Assessment Leaves Prominence

In summary, Prominence has moved Northern Hinge from a lead inventory to a quantified, audited prospective resource set, with Seabrook identified as the priority lead. The estimates carry discovery and development risk, depend on permit grants, rest on a geological chance of success of 6% to 18%, and are tied to a drilling campaign the company intends to start in mid-2027.