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NITROGEN DRILLING

Mosaic was the first company in Australia to drill a reservoir zone with pure nitrogen. This was done by the large US services company Halliburton. The technology is frequently used in North America in areas where it is thought that drilling muds may invade rock strata and block gas production, or where it is thought the use of air could lead to down-hole fires in coal seams.

Since Mosaic's first use of nitrogen in 2002, the technique has also been successfully used by Origin Energy. In such wells a hole is drilled to just above the target zone using normal drilling muds and the hole then cased with 7 inch casing. The reservoir is drilled out using nitrogen gas that is pumped down the well at high speed both to cool the drilling bit and bring rock chips to the surface. This type of drilling is 'live' and gas and oil may be produced while drilling continues.