New Pump Pressure Adjustment
Work out the new circulating pressure after a stroke-rate change or a mud weight change, without re-measuring at surface.
The Formulas Used
Where This Fits
Both calculations answer the same practical question from different directions: what should the pump gauge read once something changes, without pumping at the new condition first to find out. The stroke-rate version is what sets the slow circulating rate (SCR) pressures used directly on the kill sheet calculator — SCR readings are normally taken at reduced rate, then this same squared relationship is what a driller uses to sanity-check pressure at any other rate. The mud-weight version matters any time mud is weighted up or down mid-well and pump pressure at the same rate needs re-establishing before it can be compared against a baseline for a kick or washout indicator.
Frequently Asked Questions
Why does pump pressure scale with the square of stroke rate?
Circulating pressure losses are friction losses, and friction pressure loss through a fixed system rises with the square of flow rate. Double the strokes per minute and pressure doesn't just double — it roughly quadruples, which is why the new-strokes formula squares the ratio rather than using it directly.
Why does new pressure loss scale directly with mud weight, not squared?
Friction pressure loss is also directly proportional to fluid density — a heavier mud is simply harder to push through the same pipe and annulus at the same rate. Unlike the flow-rate relationship, that's a straight-line (linear) relationship, so the new-mud formula uses a direct ratio rather than a squared one.