The company is planning to drill 16 boreholes from the surface down to various levels, some of which will enable determination of goaf gas quantities and quality.

“The remaining boreholes will intersect coal and will enable in situ coal gas quantities and quality to be defined,” Apex said in its document lodged under the Environment Protection and Biodiversity Conservation Act.

All boreholes will enable gas extraction rates to be measured and will be drilled to variable depths up to 50 metres below the base of the Illawarra coal measures.

During gas flow testing, gas will be emitted from the boreholes. This gas will be approximately 80% methane and flaring will be undertaken to reduce the greenhouse gas effect of the emissions.

The exploration program will determine the gas potential in all the coal seams of the coal measures as well as the commercial potential of goaf gas which has collected in areas of abandoned workings, predominantly in the Bulli seam.

The proposed boreholes can be divided into three types, each of which will require different equipment and duration of exploration onsite.

The first type are open-hole boreholes drilled directly into goaf areas.

The second type are drilled into remnant coal pillars in abandoned mine workings or goafs. They are open holes from which seam core samples will be extracted and can be developed further using zero-radius drilling technology.

They will be used to determine goaf gas characteristics in underlying old Bulli seam workings. The gas will be accessed through fractures in the remnant pillars and surrounding strata.

The third type is a cored hole of about 100mm diameter, drilled over unworked areas. This hole will enable core samples from the seams within the Illawarra coal measures.