Drill Pipe

46
© Robert Gordon University and Owen S. Jenkins Ltd. 2010 ENM201 WELLS Oil & Gas Well Drilling Part 2. Prepared and presented by Owen Jenkins, BA, MA, CEng, CMarEng, FEI, MIMarEST.

Transcript of Drill Pipe

Page 1: Drill Pipe

© Robert Gordon University and Owen S. Jenkins Ltd. 2010

ENM201 WELLSOil & Gas Well Drilling Part 2.

Prepared and presented by Owen Jenkins, BA, MA, CEng,

CMarEng, FEI, MIMarEST.

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2© Robert Gordon University© Robert Gordon University and Owen S. Jenkins Ltd. 2010

Introduction to Drill Stem Design

●We’ve already seen some of the basic tools that make up the drill stem

●Let’s see how we use them.

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3© Robert Gordon University© Robert Gordon University and Owen S. Jenkins Ltd. 2010

The Work of Drilling – Remember?

●What makes drilling work?●Weight – gravity●Weight-On-Bit (WOB)●Rotation

■ Torque■Speed of rotation of the bit

●Energy stored in the rocks■Pore pressure

●A means of clearing away the debris

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The Drill String● Identification of Drill String

Credentials●Basic Functions●Yield, Tensile & Torsional

Strength●Rotary Shouldered Connections ●Buoyancy ●Overpull●Collapse & Burst Pressures● ‘Neutral Point’●Buckling●Friction Effects in Directional

Wells●REMEMBER – IT’S NORMALLY

IN TENSION

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Identification of Drill Pipe

●Data normally stamped on drill pipe to API, ISO and NORSOK standards:

●1 = Company owning pipe (e.g. KCADeutag)

●2 = Month welded (e.g. 2 = February)●3 = Year welded (e.g. 01 = 2001)●4 = Pipe manufacturer and API licence

number●5 = Drill Pipe Grade (e.g. “S”)●Range Length●API pipe will also normally bear the API

monogram

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Basic Functions

●Transmit and support axial loads●Transmit and withstand torsional loads●Transmit fluid under high pressure to

■Clean the hole■Cool the bit ■Power the MWD pulser and mud motor (if

used)● It must withstand potential fatigue damage

■ ‘Leak before break’ principle

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Stress/Strain Curve

0 0.2 0.5%

Elasticregion

Elastic limit – Yield Point

0.2% Proof stress

0.5% Strain

0.2% strain offset line, parallel to elastic region

Plastic strain region

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Yield Strength per API Spec 5D

Grade Total Extension of Gauge Length,

%E-75 0.5

X-95 0.5

G-105 0.6

S-135 0.7

●Many sources get this wrong

● They state that API specifies the 0.2% offset

● API Specs 7 and 7-1 use the 0.2% offset method for tool joints and BHA components, notdrill pipe bodies.

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Torsional Strength

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Drill Pipe Grades -Manufacture

API Grades Min Yield (lbs/in2) Symbol

E-75 (*) 75,000 EX-95 (*) 95,000 X

G-105 (*) 105,000 GS-135 (*) 135,000 S

SS-95 95,000 SS-95

G-120 120,000 G-120

Some ProprietaryGrades

Min Yield (lbs/in2) Symbol

V-150 150,000 VNote: (*) denotes commonly used grades of drill pipe

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Drill Pipe Class -Inspection

●●Per API RP7GPer API RP7G Recommended Practice for Drill Stem Design and Operating Limits (Includes Errata dated May 2000, andAddendum dated November 2003) 16th Edition August 1998

Class Number & Colour of Bands OD Wear Effect / Remaining Pipe Wall

Thickness1 (New) One White ≥87.5% nom wall

Premium Two White 80%

2 One Yellow 70%

3 One Blue <70%

Reject One Red N/A

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Which Joint is the Reject?

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Pipe Selection

●When designing the drill string for a well, plan on using PREMIUM PIPE.

●Even if pipe is new, once it is inspected in service, the highest classification used is PREMIUM, even if the pipe meets Class 1 (new) dimensions.

●Only use pipe of lower class in shallow, non-critical wells.

●We do not use anything less than Premium Class in the North Sea.

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Tensile Strength Example● What’s the yield strength of 5” Grade G

19.5 lb/ft Premium Class Drill Pipe?● First: Pipe dimensions● From tables - API RP7G or other

source, e.g. Wilson website (see link later)1. Find the I.D. or wall thickness of the tube2. 5” x 19.5 ppf – nominal wall thickness =

0.362”,so: I.D. = 5 – (2 x 0.362) or 4.276”

3. O.D.: 20% WT reduction allowable: soMin. O.D. = 5” – (0.362” x 2 x 0.2) = 5” – 0.01448” = 4.8552”

ID

Class 1 New OD

Min. Premium

OD

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Tensile Strength Example● What’s the yield strength of 5” Grade G,

19.5# Premium Class Drill Pipe?● Second: Cross Sectional Area of Steel =

(π/4)(OD2-ID2) = (π/4)(4.85522 – 4.2762) = 4.1538 sq.in.

● Grade G pipe has a Minimum Specified Tensile Yield Stress of 105,000 psi, so:

● Yield Strength of Pipe = 105,000 x 4.1538 = 436,149 lbf.

● Or 436,000 lbf. rounded to nearest 1,000.

Area of pale blue –CSA of 5”19.5# Premium Pipe = 4.1538 sq.in.

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Design Factor (or Safety Factor)

● Such tensile strengths are theoretical values based on minimum areas, wall thickness, and yield strengths

● Yield strength (as defined in API specs) is not the specific point at which permanent deformation of the material begins but the stress at which a certain total deformation has already occurred

● This deformation includes all of the elastic deformation as well as some plastic (permanent) deformation

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Design Factor (or Safety Factor)

●So: if the pipe is loaded to the extent shown in such tables, it is likely that some permanent stretch will occur;

●Moreover, there are variations in wear and wall thickness, eccentricity etc.

●To allow for these, a design factor of 85% to 90% of the tabulated value is used

●The Operator will define the SF or DF he chooses to use.

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Design Factor (or Safety Factor)

● It may be expressed as:-● A percentage e.g. 85%● A decimal number e.g. 0.85

■ So the Max. allowable stress = Yp x 0.85● Or a figure >1 e.g. 1.18

■ In which case you DIVIDE the component’s nominal yield strength by the factor to get the maximum allowable load = Yp/1.18

● Our design is always based on a percentage of yield strength, NOT ultimate tensile strength.

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Tensile Strength Example● Is that answer good enough?● That is pure tensile load.●What about torque?●What about torque + tension?●What about internal and external yield due to

pressure differences?●What about bending?●What about real life?● A combination of several of the above, most

of the time.

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Torsional Yield Strength

● Defined as the resistance of the tube to failure by a twisting torque or force.

● The torsional yield strength is based on the shear strength equivalent to 57.7% minimum yield.

● Considering pipe failure in pure torsion (zero tensile load):

● API RP7G gives us this formula:-Q = 0.096167JYm / D

■ Where Q = Min torsional yield strength, ft-lbs (i.e. lbf-ft)

■ Ym = Min unit yield strength, psi■ J = Polar moment of inertia: (π/32)(D4-d4)

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Torsional Yield Strength

●For our 5” 19.5 lb/ft grade G premium class pipe this is

●Q = 0.096167JYm / D = 0.096167 (π/32)(D4-d4) x 105,000 ÷ D

= 0.096167 x.098175(4.85524 – 4.2764) x105,000 ÷ 4.8552

= 45,200 lbf-ft. ● (or, as it so often called, erroneously, “foot-

pounds”)

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Combined Torque and Tension –Pipe Body

● API RP7G gives us this formula for combined torsion and tension:-

2

22096167.0AP

DJQ Y mT −=

● Where■ QT = minimum torsional yield strength under tension, ft-lb (sic!)■ J = polar moment of inertia■ D = outside diameter, inches■ d = inside diameter, inches■ Ym = material yield strength (sic), psi■ P = total load in tension, lbs.

and■ A = cross-sectional area, sq.in.

)(098175.0

for tubes )(32

44

44

dD

dDJ

−=

−=π

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Combined Torque and Tension –Pipe Body

●Let’s see what this means for our grade G, 5” premium class pipe body

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Combined Torque and Tension – Pipe Body5" G-105 19.5# New, Premium and 90% WT Tube Capability 1.00 SF

0

100000

200000

300000

400000

500000

600000

0 10000 20000 30000 40000 50000 60000 70000

Torque lbf.-ft.

Tens

ion

lbf.

19.5 # G-105 PremiumTube

19.5 # G-105 NewTube

19.5 # G-105 90% WT

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Tool Joints

●Drill pipe is connected together with TOOL JOINTS

●These usually conform to API Spec. 7●Standard material: 120,000 psi MSYS –

0.2% offset method.

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Stress/Strain Curve (Again)

0 0.2 0.5%

Elasticregion

Elastic limit – Yield Point

0.2% Proof stress

0.5% Total Strain

0.2% strain offset line, parallel to elastic region

Plastic strain region

For tool joints and BHA

components

For Grades E and X drill pipe. 0.6% for G

and 0.7% for S.

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Tool Joint – Box Connection

Tong space

Image edited from FPUK original

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Tool Joint – Box Connection

Image edited from FPUK original

Hardbanding (optional)

Tong space

Box Tool Joint

Friction weld External upset

Internal upset

Pipe body

Thread

Rotary Shoulder

18° tapered load shoulder (for elevators)

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Rotary Shouldered Connections

● Normal drill stem connections are Rotary shouldered connections

● The shoulder serves to seal the connection face-to-face and to transmit torque

● The threads are tapered and normally conform to API standards

● There are also proprietary threads and connections, but we shall stay with API for the time being.

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Connection Strength● Torque to yield a rotary shouldered connection

per API RP7G.

deg. thread,of angle included ½ 0.08) astaken (normally surfaces matingon friction oft coefficien

in. thread,of (pitch) lead

smaller. is whicheveror box,or pin of area sectional-cross psi. ),(stress!strength yield maximum material

ft.-lbf yield to torqueWhere

cos212

===

==

=

⎟⎠⎞

⎜⎝⎛ ++=

θ

θπ

fp

AAAY

T

fRfRpAYT

bp

m

y

stm

y

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Connection Strength

box. of area sectional-cross )]([4

grooves relief with )(4

or grooves, relieft pin withou of area sectional-cross ])[(4

in. point, gaugeat threadofdiameter pitch shoulder theof radius effective the)¼(

in. pin, oflength

thread theof radius effective the4

])625.0([:Continuing

cos212

22

22

22

121

EQODA

IDDA

IDBCA

CQODR

L

tprLCCR

fRfRpAYT

cb

RGp

p

cs

pc

pct

stm

y

−−=

−=

−−=

=+=

=

××−−+=

⎟⎠⎞

⎜⎝⎛ ++=

π

π

π

θπ

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Connection Strength

in. in. e,counterborbox in. diameter, outside

in/ft. taper,in. ation,root trunc thread

in. ted,not truncaheight height thread

in. thread, theofheight effectivemean the 2

2

in. diameter, inside :Continuing

cos212

121

83

121

81

××======

××+⎟⎠⎞

⎜⎝⎛ −=

=

⎟⎠⎞

⎜⎝⎛ ++=

tprEQODtprSH

tprSHB

ID

fRfRpAYT

c

rs

rs

stm

y θπ

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Rotary Shouldered Connection

From API RP7G

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Connection Strength

● I’m sure you’ve all memorised that!●So, that was easy, now

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Make-Up Torque (MUT)

● It is most important that a connection is done up tight enough.

● It is unusual to have too much torque applied at the surface when making-up connections.

● It is very easy to under-torque a connection

● If you do, it may well try tightening itself down-hole (“downhole make-up”)

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Box Failure From Downhole Make-up

Courtesy of FPUK Ltd.

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Make-Up Torque

●You memorised the rest earlier, didn’t you?■You didn’t?!■Hock and Shorror!

psi. level, stress up-make drecommende

SRGs. without sconnectionpin on based be shall

smaller. is whicheveror box,or pin of area sectional-cross

ft.-lbf torqueup-make Where

cos212

=

=

=

⎟⎠⎞

⎜⎝⎛ ++=

S

A

AAA

T

fRfRpSAT

p

bp

st

θπ

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Allowable Stress●Maximum make-up stress recommended

by API RP7G in rotary shouldered connections, in weaker of box or pin:

●Tool joints: 60% of minimum tensile yield (= 72,000 psi, for API tool joints)

●BHA components: 62,500 psi, except:■ 87,500 psi. for 2 7/8 PAC■ 56,200 psi. for H-90.■With a bit of luck, you’ll never need either of

these awful connections.

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Combined Torque and Tension in a Connection

NC 50 Connection, 6-5/8" OD x 2.75" ID

0

200000

400000

600000

800000

1000000

1200000

1400000

1600000

0 10000 20000 30000 40000 50000 60000 70000Applied Torsion

App

lied

Tens

ion

Shoulder SeparationPin Yield (2)Pin Yield (1)Box Yield

Recommended Area of Operation

Pin tensile failure

Shoulder separation

Box failure – hoop stress

Pin failure –combined torque and

tension

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Combined Diagram for Pipe and Tool Joint

5" G-105 19.5# New, Premium and 90% WT Tube Capability 1.00 SFWith NC50 Connections. 6-5/8" x 2¾".

0

200000

400000

600000

800000

1000000

1200000

1400000

1600000

0 10000 20000 30000 40000 50000 60000 70000

Torque lbf.-ft.

Tens

ion

lbf.

19.5 # G-105 PremiumTube19.5 # G-105 New Tube

19.5 # G-105 90% WT

Shoulder Separation

Pin Yield (2)

Pin Yield (1)

Box YieldRecommended Area of Operation

Recommended MUT:38,000 lbf-ft.

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Easier Ways

●You can look these things up in RP7G, but it does not include all pipe and connection combinations.

●Try the Grant Prideco Website:●http://www.grantprideco.com/drilling/produ

cts/drilling_products_specsTechs.asp●You will also find details of their

proprietary connections and pipe.

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References

●For derivation of drill stem strength formulae:■■ API TR 5C3API TR 5C3 Technical Report on Equations and

Calculations for Casing, Tubing, and Line Pipe used as Casing or Tubing; and Performance Properties Tables for Casing and Tubing (replaces Bull 5C2 and Bull 5C3) 7th Edition, December

2008.

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References & Bibliography● API Spec 5D Specification for Drill Pipe. 5th Edition,

October 2001.● API Spec 7 Specification for Rotary Drill Stem Elements

(Includes Addendums 1, 2 and 3) 40th Edition, November 2001.■ Covers tool joints for drill pipe only.

● API Spec 7-1/ISO 10424-1 Specification for Rotary Drill Stem Elements Petroleum and natural gas industries—Rotary drilling equipment — Part 1: Rotary Drill stem elements (Includes Addendum 1 dated March 2007) 1st Edition February 2006.

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References & Bibliography● API Spec 7-2/ISO 10424-2 Specification for Threading

and Gauging of Rotary Shouldered Thread Connections Petroleum and natural gas industries—Rotary drilling equipment — Part 2: Threading and gauging of rotary shouldered threaded Connections drill-string components. 1st Edition, June 2008.

● API RP 7G Recommended Practice for Drill Stem Design and Operating Limits (Includes Errata dated May 2000, and Addendum dated November 2003) 16th Edition, August 1998.

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ENM201 WELLS

Oil & Gas Well Drilling Part 2.

Prepared by

OWEN S. JENKINS LTD.

4, Charlton Avenue, Aboyne, Aberdeenshire, AB34 5GL, Scotland.

Tel. +44 (0)13398 87779. Mobile phone: +44 (0)7803 296779.Email: [email protected] Website: www.osjl.co.uk