Results from the West Erregulla 3 (WE3) drilling campaign demonstrate that the Carynginia shale is very likely the true upper seal for the Kingia and High Cliff sandstones, with mild to severe overpressure being observed in the deeper part of the formation in both wells to date. Whilst the overpressures in WE3 were of a magnitude requiring temporary suspension and reengineering, their presence indicates that the Carynginia shale, even where fractured, is a competent caprock. The demonstrated presence of a competent, over pressured, gas charged, caprock/source rock, coupled with data from WE2 showing the Kingia formation below it is normally pressured, suggests that the Permian structures throughout the Greater Erregulla region are likely ‘filled to spill’, in that the entire trap and associated reservoirs are likely gas saturated down to the spill point. This bodes well for extension of gas charge into all structures mapped within the Greater Erregulla region. Therefore, presence of the Carynginia shale (which has been identified on seismic over the top of South Erregulla) is a critical success factor andforms an integral part of positive well results for the deep conventional Permian gas zones.
The Dongara/Wagina sequences overlie the Carynginia and manifest at West Erregulla as a hybrid reservoir, with conventional flow units and open natural fractures intercalated within very thick units of low porosity gas sands that can store large volumes of hydrocarbon. Over 150m of this hybrid gas pay was encountered in WE3. Hydrocarbon saturation at WE3 is almost 50% higher than at WE2 suggesting that, on a relative permeability basis, the updip parts of these units will be most conducive to flow. Considerable volumes of gas were flared from these zones while drilling, with no water leg being observed in either WE2 or WE3. The hybrid, bimodal nature of these late Permian and Lower Triassic sandstones may represent a provincial, basin-centred accumulation that has regional wide upside.
WGO Price at posting:
22.5¢ Sentiment: Buy Disclosure: Held
