Drilling and well construction
Drilling and well construction are tightly regulated in Australia. The oil and gas industry has a strong understanding of the technologies involved as millions of wells have been drilled around the world in the last 160 years.
Drilling stops at regular intervals so that purpose-built steel pipes – or casing – can be installed, often in two layers.
The gap between the casing and borehole wall is filled with cement. The casing and the cement form a non-porous barrier that prevents cross-contamination between the petroleum-bearing rock formation and any overlying aquifers. The casing and cement are pressure-tested to ensure that they can tolerate higher pressures than those expected over the life of the well.
A wellhead – which contains barriers, valves, seals and a gas/water separator – is placed on the surface to maintain control of the well and the drilling rig is moved from the site.
In onshore drilling, an area is fenced off around the well, which is now ready for production. The size of this area varies. In coal seam gas operations it is usually about 15m by 15m – about half the size of a tennis court.
The drilling site is then rehabilitated.