Fresh crack at Whicher Range

EXTENDED production testing is about to begin on the Whicher Range gas field in the southern Perth Basin, Energy News can reveal, a test that could finally pave the way for the development of the closest large gas accumulation to Perth.
Fresh crack at Whicher Range Fresh crack at Whicher Range Fresh crack at Whicher Range Fresh crack at Whicher Range Fresh crack at Whicher Range

Haydn Black


Speaking yesterday, Perseverance Energy director Michael O'Reilly said the joint venture, now operated by the Warren Buffet-backed CalEnergy Resources (61.43% and operator) was rigging up in the long-delayed Western Australian program.

"We completed the well come time ago, but there were various things that slowed us down, government restrictions on flaring and fire reason, but now we're running gauges down in Whicher Range-1 and Whicher Range-4/ST1 to test the interconnectivity of the reservoir, and we expects to start the well test within the next seven days," O'Reilly said.

Whicher Range-4 was actually re-entered, deepened and completed in late 2013, however attempts to test the well last year were disrupted and delayed by a tubing leak.

A three-month EPT within EP-408 was approved by regulators last month, and the results should be known fairly quickly.

"The rubber is finally meeting the road," O'Reilly said.

Farley Riggs is operating the well test program, where the JV is hoping to see early indications of flow rates in excess of the four million cubic feet per day seen in the last test in 2008.

"Everything we have done in the past appears to have proven the completion technique that we have been investing in and our hope is, by completing the well underbalanced and stimulating the reservoir, that the geology will favour a mineral-based mud completion over previous methods used in the field," he told Energy News.

"The hope is that our methodology will be proven and there will be higher flow rates as a result, and hopefully we will have a commercial proposition."

With success, the unlisted Perseverance and its partners including Cameron Manifold's Advanced Energy Services, which share in38.57% owner Whicher Range Energy, will probably look to sell out.

"We have invested quite a bit in that, and it has been quite a drain on our shareholders to date, and we now have 15-16%, so we have no control, no loud voice at the table, and as a consequence it is probably not something to stick with, especially as we get into the development stage," he said.

CalEnergy funded all the work to earn a 50% interest, and since then the Whicher Range Energy partners have seen their equity diminish, as the Berkshire Hathaway-owned oiler has carried the burden of work.

O'Reilly suggested some of the NWS players could be interested in using Whicher Range to offset their domgas requirements, or there could be other investors keen to secure a reliable gas supply.

Whicher Range is close enough to the Dampier-to-Bunbury pipeline that it will be relatively inexpensive to build a spur pipeline to the local grid, probably for less than $10 million, although on-site power generation has also been considered in the past and remains an option.


Whicher Range is a four trillion cubic feet gas-in-place field on the edge of a high-priced, energy-hungry market, but like the 8-10Tcf Warro field in the northern Perth Basin it has always proved troublesome to tackle.

The problematic gas field was discovered in 1968, but the last company to have a serious crack at it was Amity Oil more than a decade ago.

O'Reilly said technology has moved on over the last 5-10 years, making it worth the risk to try to get the field to work.

One of the major problems with Whicher Range is that the clay soils of the Willespie Formation swell when exposed to water, destroying permeability and porosity.

An experiment using diesel as a frac fluid by Amity didn't work, but Perseverance and its partners are confident that underbalanced drilling and, eventually, horizontal wells should help overcome those issues and give the field its first test of clean, undamaged test of the native deliverability in 40 years.

In 2013 the JV re-entered the Whicher Range-4 well, and drilled the Whicher Range-5/ST1 well from 3950m.

If a commercial flow is established, above some 5mmcfpd, the plan would then be to look at developing an appraisal program.


Whicher Range is 22km south of Busselton, close to the undeveloped Wonnerup gas fields.

Both fields were found by Union Oil between 1968 and 1971, but difficulties with the fields over the decades means the southern Perth Basin really hasn't seen a lot of interest in recent years, aside from a bit of speculative CSG drilling by Westralian Gas & Power (now TTE Petroleum). More recently Pilot Energy has entered some permits to the north in the hopes of finding gas.

Whicher Range has been defined by five wells and is known to extend beyond and has a gross hydrocarbon column height of 650m.

Whicher Range-4 was originally drilled by Amity in 1997 and, when stimulated in 1999, flowed at 2.77MMcfpd day on a 3/8 inch choke, the highest result from a single zone within the field to that time, although the peak rate from all zones in the field historically was 5.5MMcfpd.

Amity drilled Whicher Range-5 in 2004, however despite attempting several techniques a gas flow could not be established, and the well flowed back gas and the experimental diesel-based frac fluids at fairly low rate.

Amity eventually sold out to private interests, and with US firm GeoPetro and Brendan Egan's Southern Amity a test was attempted in 2008, but while the initial results were promising, with the flow rate peaking at 4MMcfpd flow rates tapered off very quickly as the remnants of the frac fluid built up in the wellbore.

Schlumberger has since studied Whicher Range and suggested that with a good horizontal sidetrack using air/nitrogen underbalanced drilling techniques the field could flow anywhere between 17-20MMcfpd.

That is the basis of CalEnergy's work, and if the JV is successful there is also a lot of upside that hasn't been examined in the surrounding areas in EP 381 and EP 408.

The Whicher Range South prospect has been mapped on a few vintage seismic lines and could add around 1Tcf GIP to the project.

It was drilled with Rutile-1 in 2000 finding oil and gas shows over 130m of the Sue Group reservoir section, but was not tested due to the shows being analysed as residual.


Perseverance has one other interest, T10-1 in the coastal Perth Basin, but O'Reilly admits little has happened there, despite initial enthusiasm, and a program that saw it bid on six permits in Western Australia.

"We haven't really done anything for the last year. Unfortunately it's not the right time from a financial point of view. All of our eggs have gone into one basket into proving Whicher Range-4," O'Reilly said.

"Unfortunately, that's something we will have to hand back, which is a pity since we have put so much into it.

"We'd love to do more, but we just can't at the moment."