Reason for Revision Issued for Implementation Manual Updated as Per Revision Request 035/97-02 As per Procedural Review Scheme
1.0 PURPOSE The purpose of this procedure is to describe the most common formulae used in drilling operation.
2.0 SCOPE This procedure is applicable on all Stena Drilling Units.
3.0 RESPONSIBILITIES 3.1
Senior Toolpusher The Senior Toolpusher is responsible for the implementation of this procedure.
4.0 DEFINITIONS & ABBREVIATIONS Ref. DOP 208.
5.0
PROCEDURE
5.1 Drilling Formulae In this Section, it has been attempted to bring together formulae and methods of calculation which may be of assistance in monitoring drilling operations.
5.2
Conversion Factors Units used are English and American field units and the following are useful conversion factors if it is required to use metric units. Depth: Feet Metres
x x
0.3048 to give Metres (m) 3.2808 to give Feet (ft)
x x x
0.003785 to give Cubic Metres (m3) 0.159 to give Cubic Metres (m3) 6.2905 to give Barrels (US)
Volume: Gallon (US) Barrel (US) Cubic Metres
Pressure: psi kPa kg/cm psi
x x x x
kg/cm Bar
x x
6.895 to give Kilo Pascal’s (kPa) 0.14503 to give Pounds per Square Inch (psi) 98.1 to give Kilo Pascal’s (kPa) ( kg/m) 0.0703 to give Kilograms per Square Centimetre 14.223 to give Pounds per Square Inch (psi) 100 to give Kilo Pascal’s (kPa)
PPG (kg/m3) PPG PPG
x
119.8 to give Kilograms per Cubic Metre
x x
SG
x
lb/ft 3
x
kg/m3 kg/l kg/m3
x x x
0.12 to give Kilograms per Litre (kg/l) 0.052 to give Pounds per Square inch per Foot (psi/ft) 0.433 to give Pounds per Square inch per Foot (psi/ft) 0.00694 to give Pounds per Square inch per Foot (psi/ft) 0.00982 to give Kilo Pascal’s per Metre (kPa/m) 8.33 to give Pounds per gallon (ppg) 0.00835 to give Pounds per gallon (ppg)
Mud Weight:
Pressure Gradient: PSI/Foot kPa/Metre
x x
22.62 to give Kilo Pascal’s per Metre (kPa/m) 0.04421 to give Pounds per Square Inch per Foot (psi/ft)
Gallons per Minute
x
Barrels/Minute Cubic Metres/Minute
x x
0.003785 to give Cubic Metres per Minute(m3/min) 0.159 to give Cubic Metres per Minute(m3/min) 264.2 to give Gallons per Minute (gals/min)
x x
0.3048 to give Metres per minute (m/min) 3.2808 to give feet per Minute (ft/min)
x x x x x
0.454 to give Kilograms (kg) 908 to give Kilograms (kg) 1017 to give Kilograms (kg) 1000 to give Kilograms (kg) 2.2026 to give Pounds (lbs)
1.49 to give Kilograms/Metre 0.671 to give Pound/Foot
Determining Pit Capacities Rectangular Tanks With Flat Bottoms
5.4
Volume (bbls)
=
(L x W x D) 5.6146
where:
= = =
length of tank (ft) width of tank (ft) depth of tank (ft)
L W D
Determining Triplex Pump Outputs Output (bbl/stk)
=
( DL2 x S x 3) 1029 x 4
where:
= =
Liner Diameter (inches) Stroke Length (ft)
Output (bbl/min)
=
bbl/stk x SPM
where:
=
Strokes per Minute
=
bbl/min x 42
DL S
SPM
Output(gallons/minute)
5.5
Determining Hole Capacities Capacity (bbls/ft)
=
(Hole diameter) 1029.4
This formula can be used to determine the internal capacity of tubulars by substituting the appropriate inside diameter.
5.6
Annular Capacities Around Tubulars Capacity (bbls/ft)
=
((Hole dia) - (Tubular dia)) 1029.4
Annular capacities in casing and riser may be calculated using the same formula and substituting the relevant diameters.
5.7
Determining Critical Velocity This is the mud velocity above which flow changes from laminar to turbulent: 1.08pv + 1.08 (pv + 9.26(ID hole - OD tubular)x YP MW x (ID hole - OD tubular
5.10 Determining Ton Miles Of Drilling Service Roundtrip = where:
Roundtrip Dh Wdp Ls Wtb Wbha
Dh x Wdp x (Ls + Dh) + 2 x Dh x (2Wtb + Wbha) 5280 x 2000 = = = = = =
Round Trip Ton Miles (Rtm) Hole Depth (ft) Bouyant Weight of drill pipe in mud (lbs/ft) Average length of a stand of drillpipe (ft) Weight of travelling assembly (lbs) Bottom hole assembly weight factor Calculated by:Bouyant weight of BHA Less Bouyant weight of equiv length of Drill pipe
5.10.1
Ton Miles Drilling With DDM/Top Drives Drilling Ton Miles - Dtm Dtm Dtm Dtm where:
Dtm Rtm 1 Rtm 2
= = =
1 x (Rtm2 - Rtm1) - if hole drilled only 2 x (Rtm2 - Rtm1) - if hole reamed once 3 x (Rtm2 - Rtm1) - if hole reamed twice
= = =
Drilling Ton Miles Round Trip Tonmiles - Start of Drilling Round Trip Tonmiles - Finish of Drilling
5.10.2 Ton Miles Coring 5.10.3
These will be the same calculation as for drilling without reaming. Ton Miles Running Casing Casing Ton Miles where:
Dset Wcs Lcs Wtb
Dset x Wc x (Lc + Dset) + ( 2Dset x 2Wtb) 5280 x 2000 = = = =
Casing Setting Depth (ft) Bouyant weight of casing in mud Length of average casing joint Weight of travelling block assemblies (lbs)
5.11
Stuck Pipe Calculations Estimation of free length of stuck pipe - (Lfree): Lfree where:
5.12
e WPdp Pull diff
=
(735,294 x e x WPdp) Pull diff
= = =
Differential pipe stretch (ins) Drill pipe plain end weight (lbs/ft) Differential pull to obtain e (lbs)
Well Control Calculations These are available in the Well Control Manual WCO 200.
