via the liquid outlet 62 to the vacuum degasser 70 are largely solids free to avoid plugging of the vacuum degasser 70 gas g entrained within the liquid l is removed by the vacuum degasser 70 by differential gas liberation in accordance with conventional technology the separated gas g is then routed to the flare stack 20 for flaring with reference to fig5 and 6 in a further embodiment the wellhead 11 typically comprises blow out preventors bop 120 and a flow diverter 121 normally drilling flow passes through the open bop 120 and through the flow diverter 121 along line 98 to the separator 39 s inlet 52 these operations would be conducted substantially atmospheric pressure in cases of upset operations including higher than normal gas flows such as a kick the bop 120 closed and flow is directed to a choke manifold 122 situated between the wellhead 11 and the separator 50 a secondary and high pressure capable line 99 extends between the choke manifold 122 and the separator 50 the choke manifold 122 acts to permit higher backpressure at the wellbore which avoiding applying the same high backpressure to the separator 50 the relative flow capability into and out of the separator 50 is demonstrated by a typical matching of a 2000 psi 4 inch incoming line 99 compared to a 12 inch outgoing line from the separator gas outlet 57 the gas outlet 57 is directed to discharge to a flare pit not shown or a flare tank 102 and ignition source such as a flare 13 such an arrangement can be used in the case where extremely high volumes of combustible gas are returned to surface with drilling fluids.