7000psi mud pressures at 4.5km..., page-4

T4P - when drilling, they are circulating mud down thru the drill string and out up the well bore then this static head is being overcome by the mud pump ie. the mud is continually flowing upwards and gas naturally hitches a ride...hence it doesn't have to be of high pressure...but it has to at least be there of course!

At the point when they stop drilling (trip) there are volumes of gas travelling in the mud across the whole depth of the well. The gas volumes which are sufficiently high in the well bore (gas SG sufficiently low enough compared with mud SG to allow relative buoyancy) will continue to progressively rise to the well surface, thereby producing a higher "trip gas" reading than what is observed when the mud is flowing.

So as what's been mentioned many times previous - all very tricky to ascertain reservoir pressures until we get a clear hole to flowtest thru.......

chockers