I will respond to how we did it drilling high pressure / high density wells without MPD and then I think that will help the thinking of how MPD just accelerates the functionality and the reliability of "maintaining constant BHP".
1. One of the slides attached showed what we would do "prior" to MPD. We, Unocal, did this in the GOM when we drilled with smaller hole sizes, with high density SBM. Unocal developed a paraffin based SBM ( Saraline ) that we brought into the GOM - and our company focus was to put straws into attic reserves or new reserves as economically as possible so we could purchase leases, build a drill ship ( Discoverer Spirit ) and start drilling these leases.
That meant in reality, day to day, I would have 5 - 8 drilling rigs, drilling 8½" hole with 6¾" drill collars, 6½" hole with 4¾" drill collars, or even some time 4¾" hole using 3½" tubing with a motor on bottom that we cemented in and completed.
Most of these wells were with 16.0 to 18.0 ppg Saralie SBM - which induced a 0.6 to 1.0 ppg ECD. Drilling through depleted and ballooning reservoirs we were constantly losing fluid, or in some instances the mud we lost drilling a stand down (50 - 100 bbls) would flow back when we shut the pumps off and take hours just to get that influx out of the well because many times it flowed back with water or gas.
Hence we started the procedure of shutting the well in by staging down pumps for connections while closing the annular and staging up pumps after the connection. We used the same procedure that everyone did at every well control school since the mid 70'. We knew the equivalent pressure of our ECD and brought our pumps down and ended with the pressure we desired.
This allowed us to drill with lower density, use our ECD to control with well ( we could only take a kick while drilling ) - and then we would place the equivalent density in the hole when we started to pull out of hole. We would even calculate our pill on bottom as we were pulling out and the PWD pressures assist so much until you have to slow the pump down so much you cannot read PWD.
MPD does that for you automatically when required pressures are inputted. As seen in the slides, on different parts of the well we were trapping different pressures.
On a side note, I would more readily trust the MPD ability to keep constant BHP -more than the industry ability to keep the exact density "going into the well".
I hope these helps and one day I hope so much to be back doing this. Deep in my heart, the reason I feel we were so successful with our MPD right out of the box was the experience of what I did at Unocal so long instructing DSM and Drillers how to stop and start pumps with pressure on a well.
You will remember me attending all the Well Control Schools that I held in Jakarta as part of the preparation programme that we hired you in to do with us (Project Risk Assessments, Team Building, HAZOP, DWOPs) and I made my DSM take the classes with the Drillers and OIM off of the rig. That was critical training we went through constantly at Unocal and our Well Control Instructors and I constantly discussed the ability of each of the DSM and also any Drillers off of each rig.
Just like our Ocean Monarch - when they moved a new Driller on the rig, I went out there for when he first did his choke drills. I do not know if other companies do that or not, but every time we set casing, we had choke drills with pumps running and everyone in position -just like a kick and had to bring the pump up down and back up for each drilling on a new casing string.
I say all this because I believe it is a complete philosophy of MPD and realizing the timing of the equipment ( 18¾" annular - +/- 45 seconds to close??? ) - so I person has to have that understanding of the well down hole to under stand the invaluable benefit of MPD.
If any personal discussion is needed with this person, I deep in my heart feel that Shaun Toralde with Weatherford and myself from the Operator side, could make MPD work anywhere if we had time with the crews after the equipment is installed.
God bless you my friend. One day I will get back there to Jakarta
ps. You can forward this or use as you see fit.