## Volume height and pressure gained because of slug

a) Volume gained in mud pits after slug is pumped, due to U-tubing: Vol., bbl = ft of dry pipe x drill pipe capacity, bbl/ft b) Height, ft, that the slug would occupy in annulus: Height, ft = annulus vol., ft/bbl x slug vol., bbl c) Hydrostatic pressure gained in annulus because of slug:

HP, psi = height of slug in annulus, ft X difference in gradient, psi/ft between

Drill pipe capacity 4-1/2 in. 16.6 lb/ft = 0.01422 bbl/ft Annulus volume (8-1/2 in. by 4-1/2 in.) = 19.8 ft/bbl a) Volume gained in mud pits after slug is pumped due to U-tubing:

Vol., bbl = 184 ft x 0.01422 bbl/ft Vol. = 2.62 bbl b) Height, ft, that the slug would occupy in the annulus:

Height, ft = 19.8 ft/bbl x 32.4 bbl Height = 641.5 ft c) Hydrostatic pressure gained in annulus because of slug:

HP, psi = 641.5 ft (13.2 — 12.2) x 0.052 HP, psi = 641.5 ft x 0.052 HP = 33.4 psi

Step 3 Weight of slug, ppg:

Slug wt, ppg = 117 psi - 0.052 - 1758 ft + 12.2 ppg Slug wt, ppg = 1.3 ppg + 12.2 ppg Slug wt = 13.5 ppg

Example: Feet of dry pipe (2 stands) Slug weight slug wt and mud wt

184 ft Slug volume = 32.4 bbl 13.2 ppg Mud weight = 12.2 ppg 