18.2 ppg mud.
We stacked barite stacks on pallets to use.
South Texas is a legendary hellhole drilling deep.
In 1982 we went after a possible oolitic play at 21,000 ft.
The steel to handle a 20% H2S/ 50% CO2 gas stream could not be manufactured in the US by our partner US Steel.
We had to source the steel from Japan.
Fortunately, it was a dry hole so we did not have to produce that devil formation.
The first Bakken well I ever worked was in 1980, vertical hole, an accidental discovery (fractures) we drilled under balanced with 12.95 mud because 13.0 would knock the bottom out. Literally, just down the hill from was a well drilled to the Red River FM that had a lot less pressure at 13,500', but the sample chamber in the 'successful' DST had oil and 35% H2S. Tenneco plugged it rather than fool with keeping the flares lit and the production string together. Considering the badlands topography there and the potential for tragedy, I think they were wise. (Most ranches are at the bottom of the valleys there.) In those days, crappy flare stacks compared to today's tech blew out all too often, and the Duperow/Fryburg field up the hill often reeked of Sour Gas. To this day, there is a lot I can't smell. (My kids are under orders to let me know if I smell bad because I'm likely to miss what everyone around me can't avoid.)
The highest 'real' mud weight (polymer) I ran with was 13.8 in Wyoming, but far shallower than the deep wells in Texas. I won't say any more because I think there is an untapped field there.
I never got to work the Madden Deep, there, but it hits ~13,500 psi at ~18,000 ft. out of the Cody Sand. They burned a few rigs out that way before they got a handle on it.
Some of the early 'Bakken Fairway' horizontal wells required calcium bromide brine (14.2, but brine, not 'mud') to keep a lid on, and we flared a lot of gas while we were drilling.
Whatever it is, no matter how shallow or deep, if you're off by a pound, it can be very serious. There is no substitute for good rigs/crews/supervision and well maintained iron. I have worked over 300 wells in eight states, and none got away.
(Knock on wood, I'm not done yet!)
