Ann: West Erregulla 2 Update, page-168

M4,
They basically use Nitrogen to create a under balance environment. Aim is to create a fluid surge from the reservoir fluids into the wellbore for the pressure buildup/shut-in. When they perforate the well, they know that the reservoir pressure is higher then the hydrostatic pressure & any HC's present in the Sandstn will surge back into the wellbore and will b circulated out via the tubing thro' to the surface equipment & to the flareline. Pressure in the Kingia is around 6800 psi, so the N2 will do its part when they cleanup & do the flowback. Hope this helps.