The third stage of the Empire Energy Group’s (EEG) McArthur basin shale research program has been completed by the University of Adelaide Research Unit, the company said in a news release.

The research program focused on organic geochemistry, mineralogy and porosity of the target carbonaceous black shale intervals in the Barney Creek and Velkerri formations onshore McArthur basin, Northern Territory, Australia.

The program has identified a number of zones within the McArthur basin that show good potential for hydrocarbon prospectivity. The following summarizes key findings of the company’s Barney Creek and Velkerri core research program to date:

• TOC up to 6.4% (further research undertaken by the company has identified TOC up to 10.4% in other core samples);
• Hydrocarbon generation – ranging across the oil, oil/condensate, and wet gas generation window;
• Organic Carbon Type - Marine II and Mixed II-III;
• Tmax and hydrogen indices indicate thermal maturity ranging from early maturity for oil through late maturity for gas; and
• Pay Zones – up to 150 m (shale formations interlayered with higher porosity silt layers), the release said.

The initial research program is now drawing to a close, Empire said. The company has begun to identify segments of the basin with optimum petroleum potential and to review opportunities for the most efficient and cost effective method, including seeking potential partners, to commence the exploration and development.

Research program

From around the 900 core samples collected, the research program analyzed 133 samples from the Barney Creek and 68 samples from Velkerri formations for Total Organic Carbon (TOC)
content, the release said. From those samples, 89 Barney Creek and 35 Velkerri were further characterized by a source rock analyser (SRA) to determine their thermal maturity.

The geochemical parameters that characterize the shales are a reflection of both organic matter (kerogen) composition and the thermal maturity level of the organic matter when it generated hydrocarbons, Empire said in the release. Variations in the geochemical parameters allow the determination of whether the shale source rock formation remains immature, in the early oily window, at peak oil generation, in the late oil window, in the zone of condensate and wet gas generation, or dry gas window, or post mature.

Thermal maturity measures to what degree the source rocks reached temperatures and pressures sufficient to achieve maturity and if so whether they have already generated and expelled hydrocarbons. This is in effect a snapshot of the hydrocarbon generating capacity and organic carbon type, the release said.

Results

Due to the significant area over which the core samples were distributed in or around the company’s southern and central tenements, (Batten Trough and Urupunga Fault Zone), there is a variance between the results from the core samples tested, the release said.

In the Barney Creek formation, TOC values ranged up to 6.4%. Further, TOC values show the Barney Creek formation has two to four horizons that are good to excellent for prospective hydrocarbon generation of oil and gas. The Barney Creek Formation has prospective pay zones up to 140m thick. The general trend is for the principal zone to be 20 m to 40 m thick, according to the release.

In summary, organic geochemical parameters indicate that the Barney Creek core studied lies in the late immature to mature oil generation window with the highest prospective zones in the oil/gas prone to oil marine prone generation state.

Thermal maturity varies across the Barney Creek formation core studied, but generally varies within the good to excellent zone, according to the release. Core results were generally type II and Mixed II-III kerogen (type II equals oil prone-generally marine; type II-III equals oil/gas prone).

In the Velkerri formation, TOC values ranged up to 5.7%. Further TOC values show the Velkerri formation has two horizons that are good to excellent for prospective hydrocarbon generation for oil and gas. The Velkerri Formation has prospective pay zones up to 150m thick. The general trend is for the principal target zone to be 30 m to 40 m thick, the release said.

In summary, organic geochemical parameters indicate that the Velkerri core studied lie in the oil/condensate wet gas window. A few occasional samples were in the dry gas/post mature window, according to the release.

Thermal maturity varies across the Velkerri Formation core studied, but generally lies within the Good to Excellent Zone, over the prospective sections measured. Core results were generally type II-III/III kerogen (type III = gas prone).

Next stage

As the initial research program draws to an end, the company said it will start the process of integrating thermal maturity results into the regional 3-D geo-model of the McArthur basin which has now been completed by the company. The results from integration of these data will allow the company to construct a series of ‘Common Risk Segment’ maps. These will indicate those segments of the basin where the target shales have the optimum depth, geological structure and geochemical parameters to be the focus for the initial exploration programs.

The preliminary emphasis will be to further develop the most prospective shale common risk segment areas and conventional structures identified during the course of the geo-modeling, which currently includes, and is not limited to: 26 potential conventional structures with EP(A)180, 181 and 182; and a potentially highly prospective unconventional shale outlier within EP187, similar in nature to the Myrtle sub-basin, along with a further 8 potential conventional structures in EP187; and will continue to integrate new and additional data that will become available during 2013-2014. These areas are likely to be progressed as initial exploration drilling locations in 2014-2015, the release said.