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When to take SCRs
23 December 2019

A post on the Facebook page of a IWCF/IADC Training  provider  asked the question of viewers “How often should you take Slow Circulating Rate Pressures”

For me the correct answer was missing!

With the possible  exception of establishing the friction pressure losses in deepwater choke lines I would respectfully argue that the correct answer should be “almost never”.  

Taking SCR pressures represent one of the largest “hidden Non-Productive Time “in drilling.   At best they provide an estimate for what the standpipe pressure might be after bringing up the pumps to kill speed but only that.  How many $million does your company spend on these measurements each year?  

Calibrated hydraulics software can provide the same estimate at a fraction of the cost.  The calibration does not have to be performed with measurements taken multiple times daily .. PWD data (if available) or simply the standpipe pressure measurements at full drilling rates provides mre than adequate calibration data.

 You never actually use the data anyway...   you should Never “force” Pstandpipe to match SIDPP + Pscr. You may have plugged one or more nozzles, have a cuttings load in the annulus etc.  With  surface BOPs, keep choke pressure constant  while bringing up the pumps. For shallow  subsea BOPs keep the kill line pressure constant and in deepwater  keep the BOP cavity pressure constant.

The  standpipe pressure you end up with is the correct value.  If it is way off the expected value then stop and check why. 

Spend (some of) the millions you save  by not wasting time on these  largely irrelevant measurements by investing in a drilling choke and control system  that actually does what you want it to do...hold the choke pressure at a target pressure not a fixed choke size.  

Happy holidays everyone!

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