Amount of cuttings produced per foot of hole and total solid generated

After learning about capacity calculation, we can apply the capacity calculation to determine how much barrels of cutting produced per foot of hole drilled and total solid generated in pounds.

Please read and understand the following formulas:

Use formula#1 and #2 for calculating amount of cutting generated per feet drilled.

Formula#1 for BARRELS of cuttings drilled per foot of hole drilled:

Barrels of cutting per foot drilled = Dh2 x (1 – % porosity) ÷1029.4

Where: Dh is hole diameter in inch.

Example: Determine barrels of cuttings drilled for one foot of 6-1/8 inch hole with 25% (0.25) porosity:

Barrels/footage drilled = 6.1252 x (1 – 0.25) ÷1029.4
Barrels/footage drilled = 0.02733 bbl/footage drilled

Formula#2 for CUBIC FEET of cuttings drilled per foot of hole drilled:

Cubic feet of cutting per foot drilled = Dh2 x 0.7854 x (1 – % porosity) ÷144

Where: Dh is hole diameter in inch.

Example: Determine barrels of cuttings drilled for one foot of 6-1/8 inch hole with 25% (0.25) porosity

Cubic feet/footage drilled = 6.1252 x 0.7854 x (1 – 0.25) ÷144
Cubic feet/footage drilled = 0.153462 cu ft/footage drilled

Moreover, you also apply sample density and volume relationship to determine total solids generated. Use the following formula to calculate total solid generated.

Wcg = 350 x Ch x L x (l – porosity) x Cutting density

Where;

Wcg = solids generated in pounds
Ch = capacity of hole in bbl/ft
L = footage drilled in ft
Cutting density = cutting density in gm/cc

Example: Determine the total pounds of solids generated in drilling 100 ft of  6-1/8 inch hole (0.03644 bbl/ft). Density of cuttings = 2.20 gm/cc. Porosity = 25%:
Wcg = 350 x 0.03644 x 100 x (1 – 0.25) x 2.2
Wcg = 2104.41 pounds

Please find the excel sheet how to calculate how much cuttings drilled per foot of hole drilled and total solids generated

Ref book: Drilling Formula Book Formulas and Calculations for Drilling, Production and Workover, Second Edition

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Calculate inner capacity of open hole/inside cylindrical objects

From the previous post, you learn how to calculate annular capacity and this post shows you how to use the same principle to calculate inner capacity of  open hole / inside cylindrical objects such as tubulars, drill pipe, drill collars, tubing, casing etc.

There are several formulas to calculate inner capacity depending on unit of inner capacity required. Please read and understand the formulas below:

Formula#1) Calculate inner capacity in bbl/ft

Inner Capacity in bbl/ft = (ID in.)2 ÷1029.4


Example: Determine inner capacity in bbl/ft of a 6-1/8 in. hole:
Inner Capacity in bbl/ft = 6.1252÷1029.4
Inner Capacity in bbl/ft = 0. 0364 bbl/ft

Formula#2) Calculate inner capacity in ft/bbl

Example: Determine inner capacity in ft/bbl of 6-1/8 in. hole:
Inner Capacity in ft/bbl = 1029.4 ÷ 6.1252
Inner Capacity in = 27.439 ft/bbl

Inner Capacity in ft/bbl = 1029.4 ÷ (ID in.)

Formula#3) Calculate inner capacity in gal/ft

Inner Capacity in gal/ft = (ID in.)2 ÷24.51

Example: Determine inner capacity in gal/ft of 6-1/8 in. hole:
Inner Capacity in gal/ft = 6.1252÷ 24.51
Inner Capacity in = 1.53 gal/ft

Formula#4) Calculate inner capacity in ft/gal

Inner Capacity in ft/gal = 24.51 ÷ (ID in.)2

Example: Determine inner capacity in ft/gal of 6-1/8 in. hole:
Inner Capacity in ft/gal = 24.51 ÷ 6.1252
Inner Capacity in ft/gal = 0.6533 ft/gal

Determine the volume of mud to fill up the inner of the cylindrical objects by the following equation.

Inner Volume = Inner Capacity x Lenght

Example: Inner capacity =  0. 0364 bbl/ft

Length = 3000 ft

Volume = 0. 0364 x 3,000 = 109.2 bbl.

Please find the excel sheet on how to calculate inner capacity.

Ref book: Drilling Formula Book Formulas and Calculations for Drilling, Production and Workover, Second Edition

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Calculate Annular Capacity

Annular capacity is one of basic values that you really need to understand. This post demonstrates you how to calculate annular capacity between casing or hole and drill pipe, tubing, or casing. There are several formulas as shown below to calculate annular capacity depending on unit of annular capacity required.

Note: Dh is bigger ID and Dp is smaller OD. The examples below will show the Dh as hole size and Dp is drill pipe OD

a) Calculate annular capacity in bbl/ft

Annular capacity in bbl/ft =  (Dh2 – Dp2) ÷1029.4

Example: Hole size (Dh) = 6-1/8 in.
Drill pipe OD (Dp) = 3.5  in.
Annular capacity in bbl/ft = (6.1252 – 3.5 2) ÷1029.4
Annular capacity = 0.0245 bbl/ft

b) Calculate annular capacity in ft/bbl

Annular capacity in ft/bbl = 1029.4 ÷ (Dh2 – Dp2)

Example: Hole size (Dh) = 6-1/8 in.
Drill pipe OD (Dp) = 3.5  in.
Annular capacity in ft/bbl = 1029.4 ÷ (6.125 2 – 3.5 2)
Annular capacity = 40.743 ft/bbl

c) Calculate annular capacity in gal/ft

Annular capacity in gal/ft = (Dh2 – Dp2) ÷ 24.51

Example: Hole size (Dh) = 6-1/8 in.
Drill pipe OD (Dp) = 3.5  in.
Annular capacity in gal/ft = (6.125 2 – 3.52) ÷24.51
Annular capacity = 1.031 gal/ft

d) Calculate annular capacity in ft/gal

Annular capacity, ft/gal = 24.51 ÷ (Dh2 – Dp2)

Example: Hole size (Dh) = 6-1/8 in.
Drill pipe OD (Dp) = 3.5  in.
Annular capacity in ft/gal = 24.51 ÷  (6.125 2 – 3.5 2)
Annular capacity in ft/gal = 0.97 ft/gal

Annular volume can be determined by this following formula;

Annular volume in bbl  = annular capacity (bbl/ft) x length of annulus (ft)

Note: annular volume can be expressed in several unit depending on unit that you use in the calculation.

Example:

Annular capacity = 0.0245 bbl/ft
Length of annulus = 1000 ft

Annular volume = 1000 x 0.0245 = 24.5 bbl.

** Please remember that if you have several annular profile, you must calculate volume based on each annular profile in order to get total annular volume.

Please find the Excel sheet for calculating annular capacity.

Ref book: Drilling Formula Book Formulas and Calculations for Drilling, Production and Workover, Second Edition

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Calculate Equivalent Circulation Density (ECD) with complex engineering equations

These formulas below are used for complex calculation for annular pressure loss and equivalent circulating density. I think this calculation will give you more accurate result than a simple equation. Please follow the following steps how to calculate annular pressure loss and ECD.

1. Determine n:

1-determine n
2. Determine K:

2 determine k
3. Determine annular velocity (v) in ft/min:

3 annular velocity

4. Determine critical velocity (Vc) in ft/min:
4 determine vc

5. Pressure loss for laminar flow (Ps), psi:

5 Pressure loss for laminar flow

6. Pressure loss for turbulent flow (Ps), psi:
6 Pressure loss for turbulent flow

7. Determine equivalent circulating density (ECD), ppg:

7 ECD

Abbreviation meaning

θ300: viscometer dial reading at 300 rpm
θ600: viscometer dial reading at 600 rpm
Q: Flow rate in gpm
Dh: Diameter of hole
Dp: Diameter of drill pipe, drill collar or BHA in ft
v: annular velocity in ft/min
L: length of drill pipe, drill collar or BHA in ft
MW: Mud Weight
PV: Plastic viscosity

Example: Equivalent circulating density (ECD) in ppg by using following data:

Mud weight = 9.5 ppg
θ300 = 40
θ600 = 60
Plastic viscosity = 20 cps
Circulation rate = 650 gpm
Hole diameter = 8.5 in.
Drill collar OD = 6.75 in.
Drill pipe OD = 5.0 in
Drill collar length = 600 ft
Drill pipe length = 10,000 ft
True vertical depth = 9,000 ft

1. Determine n:

example 1-determine n

2. Determine K:

example 2 determine k
3. Determine annular velocity (v) in ft/min around drill pipe:

example 3 annular velocity around drill pipe

 

4. Determine critical velocity (Vc) in ft/min around drill pipe:

example 4 determine vc around drill pipe

The annular velocity around drill pipe is less than the critical velocity around drill pipe so this is laminar flow. The equation #5 (for laminar flow) must be applied in this case.

Pressure loss for turbulent flow (Ps), psi:

example 4 determine pressure loss around drill pipe

5. Determine annular velocity (v) in ft/min around drill collar:

example 5 annular velocity around drill collar

6. Determine critical velocity (Vc) in ft/min around drill collar:
example 6 determine vc around drill collar

The annular velocity around drill collar is more than the critical velocity around drill collar so this is turbulent flow. The equation #6 (for turbulent flow) must be applied in this case.

Pressure loss for laminar flow (Ps), psi:
example 6 determine pressure loss around drill collar

Total annular pressure loss = annular pressure loss around drill pipe + annular pressure loss around drill collar

Ps=271.3+81.5 = 352.8psi

7. Determine equivalent circulating density (ECD), ppg:

Example 7 ECD

Please find the Excel sheet for calculating ECD (engineering calculation)

Ref book: Drilling Formula Book Formulas and Calculations for Drilling, Production and Workover, Second Edition

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