Basic Drilling Formulas
Capacity Formulas

Capacity Formulas

Basic Drilling Formula for calculating Annular capacity between casing or hole and drill pipe, tubing, or casing

a) Annular capacity, bbYft = Dh2 - Dp2 1029.4
Example: Hole size (Dh) = 12-1/4in. Drill pipe OD (Dp) = 5.0in.
Annular capacity, bbVft = 12.252 - 5.02 1029.4
Annular capacity = 0.12149bbYft

b) Annular capacity, ft/bbl = 1029.4 (Dh2 - Dp2)
Example: Hole size (Dh) = 12-1/4in. Drill pipe OD (Dp) = 5.0in.
Annular capacity, ft/bbl = 1029.4 (12.252 - 5.02)
Annular capacity = 8.23fthbl

c) Annular capacity, gaVft = Dh2 - Dp’
24.51 Example: Hole size (Dh) = 12-1/4in.
Drill pipe OD (Dp) = 5.0in. Annular capacity, gaVft = 12.252 - 5.02
24.51 Annular capacity = 5.lgaYft

d) Annular capacity, ft/gal = 24.51 (Dh2 - Dp2)
Example: Hole size (Dh) = 12-1/4in. Drill pipe OD (Dp) = 5.0in.
Annular capacity, ft/gal = 24.51 (12.25*- 5.02)
Annular capacity = 0.19598ftlgal

e) Annular capacity, ft3/linft = DhZ- Dp2
183.35 Example: Hole size (Dh) = 12-1/4in.
Drill pipe OD (Dp) = 5.0in. Annular capacity, ft3/linft = 12.25*- 5.02
183.35 Annular capacity = 0.682097ft3/linft

f ) Annular capacity, linft/ft3 = 183.35 (Dh2 - Dp2)
Examule: Hole size (Dh) = 12-1/4in. Drill pipe OD’(Dp) = 5.0in.
Annular capacity, linft/ft3 = 183.35 (12.252- 5.02)
Annular capacity = 1.466linft/ft Annular capacity between casing and multiple strings of tubing

a) Annular capacity between casing and multiple strings of tubing, bbl/ft:
Annular capacity, bbYft = Dh2 - + (T2)2] 1029.4
Example: Using two strings of tubing of same size:
Dh = casing-7.0in.-29lb/ft TI = tubing No. 1-2-3/8in. T2 = tubing No. 2-2-3/8in.
I D = 6.184in. OD = 2.375in. OD = 2.375in.
Annular capacity, bbVft = 6.1842 - (2.3752 + 2.3752) 1029.4
Annular capacity, bbVft = 38.24 - 11.28 1029.4
Annular capacity = 0.02619bbYft

b) Annular capacity between casing and multiple strings of tubing, ft/bbl:
1029.4 Dh2 - [UJ2+ (T’)*]
Annular capacity, ft/bbl = Example: Using two strings of tubing of same size:
Dh = casing-7.0in.-29lb/ft TI = tubing No. 1-2-3/8in. T2 = tubing No. 2-2-3/8in.
ID = 6.184in. OD = 2.375in. OD = 2.375in.
Annular capacity, ft/bbl = 1029.4 6.184’ -(2.3752+2.375’)
Annular capacity, ft/bbl = 1029.4 38.24 - 11.28
Annular capacity = 38.1816ftlbbl

c) Annular capacity between casing and multiple strings of tubing, gal/ft:
Annular capacity, gaVft = Dh2 - [(T,)’ + (T?)’] 24.5 1
Example: Using two tubing strings of different size:
Dh = casing-7.0in.-29 lb/ft TI = tubing No. 1-2-3/8in. T2 = tubing No. 2-3-112in.
ID = 6.184in. OD = 2.375in. OD = 3Sin.
Annular capacity, gaVft = 6.1842 - (2.375’ + 3.5’) 24.5 1
Annular capacity, gaVft = 38.24 - 17.89 24.5 1
Annular capacity = 0.8302733gaVft

d) Annular capacity between casing and multiple strings of tubing. ft/gal:
Annular capacity, ft/gal = 34.51
Dh2 - [(T,)’ + (T?)’] Example; Using two tubing strings of different sizes:
Dh = casing-7.0in.-29lb/ft T, = tubing No. 1-2-3/8in. T2 = tubing No. 2-3-1/2in.
ID = 6.184in. OD = 2.375in. OD = 3.5in.
Annular capacity, ft/gal = 24.51 6.184’ - (2.3752+3.5’)
Annular capacity, ft/gal = 24.51 38.24 - 17.89
Annular capacity = 1,2044226fuga1

e) Annular capacity between casing and multiple strings of tubing, ft3/linft:
Annular capacity, ft3/linft = Dh2 - [VJ2+ (T2I2] 183.35
Example: Using three strings of tubing: Dh = casing-9-98 i n . 4 7 lb/ft
TI = tubing No. 1-3-1/2in. T2 = tubing No. 2-3-1/2in. T3 = tubing No. 3-3-1/2in.
ID = 8.681in. OD = 3.5in. OD = 3.5in. OD = 3.5in.
Annular capacity - Annular capacity, ft3/linft = 183.35
- 8.6812- (3S2+3S2+3S2)
183.35 75.359 - 36.75
Annular capacity = 0.2105795ft3/linft

f ) Annular capacity between casing and multiple strings of tubing, linft/ft3:
183.35 Dh2 - [(T,12+ (T212]
Annular capacity, linft/ft3 = Example: Using three strings tubing of same size:
Dh = casing-9-5/8 in.47lblft TI = tubing No. 1-3-1/2in. TI = tubing No. 2-3-1/2in. T, = tubing No. 3-3-1/2in.
ID = 8.681in. OD = 3.5in. OD = 3.5in. OD = 3.5in.
- - 8.6812 - (3.52 + 3.52 + 3.52)
183.35 75.359 - 36.75
Annular capacity Annular capacity, linft/ft3 = 183.35
Annular capacity = 4.7487993linft/ft3 Capacity of tubulars and open hole: drill pipe, drill collars, tubing, casing, hole, and any cylindrical object

a) Capacity, bbVft = ID, in? ~ 1029.4
Basic Formulas 17 E-xumple: Determin-e the capacity, bbl/ft, of a 12-1/4in. hole:
Capacity, bbVft = 12.25’ 1029.4
Capacity = 0.1457766bbVft

b) Capacity, fthbl = -1029.4
Dh’ E.xample; Determin-e the capacity, ft/bbl, of 12-1/4in. hole:
Capacity, ftlbbl = 1029.4 12.252
Capacity = 6.8598fdbbl

c) Capacity, gaVft = ID, in.?
~ 24.51 Example; Determi-ne the capacity, gal/ft, of 8-1/2in. hole:
Capacity, gaVft = 8.52 24.51
Capacity = 2.9477764gaVft

d) Capacity, ftlgal = 24.5 1
~ ID. in.’ Exumple; Determi-ne the capacity, ft/gal, of 8-112in. hole:
Capacity, ft/gal = 24.51 8.5’
Capacity = 0.3392ftlgal

e) Capacity, ft3/Iinft = -ID2
183.35 E.xarnple; Determine-the capacity, ft3/linft,for a 6.0in. hole:
Capacity. ft3/Iinft = 6.0’ 183.35
18 Formulas and Calculations Capacity = 0.1963ft3/linft
Capacity, Iinft/ft3 = 183.35 ~ ID,in.2

f )Amount of cuttings drilled per foot of hole drilled

a) BARREL-S of cuttings drilled per foot of hole drilled:
Example: Determine-thecapacity,linft/ft3,fora6.0in.hole: Capacity, linft/ft3 = 183.35
6.02 Capacity = 5.093051inft/ft3
Barrels = Dh2 1029.4(' -
9'0 porosity)
Example: Determine the number of barrels of cuttings drilled for one -foot of 12-1/4in.-hole drilled with 20% (0.20) porosity:
12.252 (1 - 0.20) Barrels = 0.1457766 x 0.80
Barrels = 1029.4
Barrels = 0.1166213

b) CUBIC FEET of cuttings drilled per foot of hole drilled:
Cubic feet = -Dh2 x 0.7854(I - %porosity) 144
Example: Determine the cubic feet of cuttings drilled for one foot of 12--114in. hole with 20% (0.20) porosity:
12'252 x 0.7854(1 - 0.20) 144
Cubic feet = Cubic feet = 150.0626 x 0.7854 x 0.80
144 Cubic feet = 0.6547727

c) Total solids generated: Wcg=350ChxL(1-P) SG
where W,, = solids generated, pounds Ch = capacity of hole, bbl/ft L = footage drilled, ft SG = specific gravity of cuttings P = porosity, o/o
E.uample; Determine the total pounds of solids generated in drilling l00ft of a 12-1/4in. hole (0.1458bbl/ft). Specific gravity of cuttings = 2.40gm/cc. Porosity = 20%.
Wcg = 350 x 0.1458 x 100(1 - 0.20) x 2.4 Wcg = 9797.26 pounds