The block is immediately east of the giant Bayu-Undan gas-condensate filed in the JPDA and was released as WA15-2.

In addition to Bayu-Undan, and that field's key pipeline, the Laminaria, Corallina, Kitan, Jahal and Kuda Tasi that collectively contained some 280MMbbl are within 15km. The Kakatua and Elang oil fields lie just 25-40km to the east of WA-523-P.

Laminaria-Corallina has an existing FPSO development that was recently purchased by start-up Northern Oil & Gas Australia.

WA-523-P has "outstanding development potential", Carnarvon managing director Adrian Cook said.

"This area of the North West Shelf has tremendous opportunity and is an important addition to our portfolio," he said.

"We believe we can generate significant shareholder value by applying cutting edge seismic imaging technologies which have recently proven successful in our Phoenix permits.

"These modern processes will provide a step-change improvement in the definition of prospects, determination of volumes and reduction of drilling risk.

The company acquired the block "for a fraction of the cost of the commitments made by peers in bid rounds only a year or two ago" and exposes the company to an area where some 1.3 billion barrels of oil equivalent has been discovered to date.

The work program for the initial three years is for relatively inexpensive reprocessing of existing 3D seismic data, work that should be committed within the next 12 months.

That work has already started.

Further 3D seismic and a drilling commitment sit within the second discretionary permit term.

The 4220sq.km block increases Carnarvon's footprint on the NWS to some 18,700sq.km net acres, with its crown jewel being the Bedout Sub-basin blocks around its Roc-1 and Phoenix South-1 discoveries. An appraisal of the Roc discovery is expected in July.

It also has an interest in the Cerberus blocks in the shallow NWS where drilling is gaining environmental approval; WA-155-P(1), where it is about to spud the Outtrim West-1 well with Quadrant Energy; and the recently awarded WA-521-P in the Rowley Sub-basin.

Carnarvon said there are numerous undrilled horst blocks within the block, and significant opportunity suggested by the number of wells that have intersected live oil or good oil shows, and by the distribution of the undrilled structures.

The new block contains the depleted 20MMbbl Buffalo oil field that was reservoired in the Elang Formation and the undeveloped oil discoveries in the Bluff-1 and Buller-1 wells.

Buffalo was discovered in 1996, flowing at 11,790bopd of 52.7 degree light oil on test.

Buffalo-1 was drilled in 27m of water, finding a 32m net oil column.

Bluff-1 was drilled in 1998 in 109m of water, intersecting a 16m net sand from which a 56 degree API oil light oil sample was taken, while Buller-1 was drilled in 1997 in 115m of water finding a 9m oil sand, with a 52 degree API sample of oil taken.

Cook said either discovery may prove to be commercially significant if the new imaging reveals volumetric upside.

Of the 14 wells drilled within the block, eight were dry. The balance had oil or gas shows, including SAGASCO Resources' 1993 test Rambler-1, which found background gas over 86m in the Plover Formation with oil samples also recovered.

Carnarvon said it appeared that the absence of accurate seismic depth imaging of the target reservoirs has resulted in a very poor track record for well depths coming in on prognosis, even when they are drilled close to existing well control.

This problem in getting the depth mapping right has resulted in major difficulty defining field development locations and prospects, describing volumes, reducing risk and justifying drilling.

Carnarvon's aims to address these historical depth imaging challenges by using modern processes that the company has been testing on other permits in its portfolio over the past few years, such full waveform inversion to provide higher resolution velocity field measurement for input to pre-stack depth migration, improving image depth.

The Sahul Syncline, is a prominent Palaeozoic to Mesozoic northwest‑trending troughs located between the Londonderry and Flamingo highs in the northern Bonaparte Basin that are the source of the petroleum accumulations on the adjacent Laminaria and Flamingo highs.

The main target formations are the Plover, Elang and Frigate sands, however the Echuca Shoals Formation and Bathurst Island Group may also have some hydrocarbon potential in the region.

Rambler-1 tested a Mesozoic fault block in the southwest flank of the Sahul Syncline which is less well understood.

The main risks in the northern Bonaparte Basin are seal, with fault reactivation, particularly in the Neogene, an issue, and inconsistent reservoir distribution.

Although proven petroleum systems and traps have been identified in the region, a detailed understanding of reservoir distribution and fault-associated migration pathways in the relatively underexplored Sahul Syncline is needed.