gdy 105 million jv origin energy, page-75

Thanks kashga, that is all interesting to learn and is much better than trying to guess and deduce things, getting much of it wrong.
I always thought that applying the required thrust to the bit would be a matter of actually suspending the weight of the whole string and then just lowering it sufficiently that the bit would only be supporting a fraction of the load.
I had guessed this as when you get kilometers of drill pipe in the string it would damm near crush the bit assembly, certainly not make for an optimum drilling action. So, good.

I had not thought about the fact that as the rig supported most of the drill string weight,(many many tonnes), that this would mean the string was in tension and no doubt this also assists keeping it rigid??

You mention the 'stabilisers'. If these are 12-1/2" in diameter, same as the bit, hence same as the actual hole size. How does the mud pass back up the hole past these?

Perhaps you can give me some 'clarification' on these Q'S
and maybe ring the Innaminka pub and check if any of your old mates happen to be at the bar and can fill you in on what's happening down at the drill head!

cheers,
geojac