In order to produce CSG, a well is typically drilled to a depth of between 500m–1,000m to intersect the gas bearing coal seams. Steel casing is cemented into the well bore to isolate the hole from all surrounding stratigraphy and to seal it from the surrounding environment. The casing is then perforated at the depth of the coal seam, to further isolate the gas extraction zone. Hydraulic fracture stimulation is where a sand and water mixture is pumped into the coal seam through the perforations at the target zone at high pressure until the coal structurally cracks. Fractures propagate horizontally from the well bore, typically in two directions. These fractures, deep in the coal seam, have no effect on the ground surface. The injected sand is used as a proppant to prevent the fractures from fully closing. Essentially the sand is squashed by the coal seam and the sand in the coal establishes a porous pathway, enabling previously trapped gas to flow into the well bore. After the fracture stimulation, a work-over rig installs production tubing in the well, a pump (if required) and surface facilities (well head, piping and instrumentation, etc). The water pump may be required for a short time to extract excess water from the coal seam. The gas extracted from a completed well that is in production flows through a gathering line network, under its own pressure. Gas production is dependent on many factors. These typically include the thickness of coal gas content, permeability (ability for the gas to flow), depth of the coal seam and purity of the gas. CSG is typically found at depths ranging between 400m – 1,000m. These shallower depths make it possible to use smaller, more mobile, truck-mounted drilling rigs than those used for conventional gas. This reduces the surface foot print of the activity and improves exploration cost efficiencies.