how does pulsation dampner settings effect mwd?

[brent217]

Hi guys, I am an MWD (Measurement While Drilling) Engineer with Sperry-Sun Drilling Services. I have an MWD manual that says a the pulsation dampner on a drilling rig should be set to between 30 and 40% of standpipe pressure in order for me to get the optimal pulse size from my MWD (positive pulse) tool, but my manual does not say why.

I have been asked at work to find out what happens if the pulsation dampner is set at 0%, 10%, 20% ... 100%, and 200% of standpipe pressure.

I know that at 0% there is simply no dampning effect on either my tool or the pump's pulses.

I have talked to several tool pushes that think that at 100%+ the pulsation dampner is also effectiveless, as they say that if the rubber bladder has the same pressure as the standpipe it cannot absorb anything, but I am not sure.

I have personally never seen a pulsation dampner with more than 40%, so I have no direct experience to compare to. Anyone have any ideas, or can link me to a manual that explains exactly how a pulsation dampner absorbs pulses in the standpipe, and how the diferent settings are derived?

 

[DrillEng]

The pulsation dampener has mud on one side and pressurised nitrogen on the other is actually in place to absord the pressure differences from the triplex pump piston action. The pulsation dampener will isolate the pump noise from your standpipe signal or tries to. No pressure in the pulsation dampener, and trust me you will get no signal or very little signal from your tools that you can process. Also your surface system will get heavy pressure surges that could be damaging.
By increasing the pressure you should get a better signal upto a point. You need to have them set at the rig prescribed pressure. This is usually quite adequate. Also the drilling contractor will not be inclined to change his prescribed pressures as this may mean burst bladders, more maintenance and damage to his equipment.

 

[brent217]

Thanks.

 

[roadie]

Brent217,

You had one reply. His answer is correct. However you need to also need to understand where your transducer is in respect to the pumps. There are dead zones in the system where signal detection is horrible. Anadrill(my former employer 10 yrs)used differential detection to cancel out noise. We had a sensor near the top of the standpipe(tricky on topdrives).

My advise, always carry weldolets to mount your sensor and give the pusher a free bladder if his blows up. Keep up the pressure in the bladder saves his equipment also.