MELBOURNE, Nov. 10 -- Australian Worldwide Exploration Ltd. (AWE), Sydney, intends to follow up what it sees as a major reserve potential in shale gas and tight gas acreage in the North Perth basin of Western Australia after analysis of the Woodada Deep-1 well suggested a resource of as much as 20 tcf of gas.
AWE reentered Woodada Deep-1 in April and carried out a core program and logging run across the prospective Carynginia shale formation, which has three distinct shale intervals.
As a result, the company estimates that the middle shale section alone holds gross gas-in-place of 13-20 tcf. Using the recovery yardstick of 20% recovery, the recoverable reserve potential is in excess of 4 tcf.
The gas estimate is backed up by a drillstem test run some years ago in the Arowsmith-1 well about 25 km from Woodada Deep-1 which flowed at estimated rates up to 4 MMcfd without fracture stimulation before the flow subsequently declined.
AWE says the Carynginia shale has similar characteristics to some of the productive shale units in the US. It is more than 280 m thick and lies at a subsurface depth of 2,500-3,500 m.
AWE has about 620,000 net acres of prospective shale gas acreage in the Perth basin with high levels of equity and operatorship in most of the permits.
The company has been evaluating the region for 2 years—the Woodada Deep-1 program being its first physical test of the shale gas potential.
Further work will be needed to ascertain commercial viability, but it is greatly enhanced by the proximity to existing pipeline and production infrastructure along with the strong demand and pricing of domestic gas in Western Australia.
The next step will be a fracture stimulation test in the middle section of the Carynginia likely to be carried out in 2011.
The company also is working on comprehensive geological models for three shale gas targets in the basin—the Carynginia, the Kockatea shales, and the Irwin River Coal Measures (IRCM)—to high-grade sectors and delineate targets for a drilling campaign to begin in mid-2011.
The Kockatea shale is extensive across the basin and up to 600 m thick in AWE’s permits. It contains proven source rocks for oil and gas fields in the region, including the nearby Woodada field.
IRCM also extend right across the basin and are known to generate gas although the formation is very tight. AWE fracture stimulated a well called Corybus-1 in 2009 and connected it to the nearby Dongara gas processing facility. It flowed initially at 4 MMcfd and is still producing at 1.2 MMcfd.
In the light of these results AWE is reinterpreting the existing seismic data in the region to assess the tight gas potential of Corybus and nearby structures.