Drill String Standards

Basic Drill String Standards

DRILLING PRACTICES

BASIC DRILL STRING STANDARDS

Understand the basic principles of engineering mechanics that are involved in Drill String Standards and Drilling Tubular Failures.

Demonstrate a knowledge of the following :

drillpipe Ranges,Grades and Terminology. API and Numbered Connections. Tool Joint Upsets. Pipe Identification. Drilling Tubular Function. Fatigue Failures. Tension and Torsion Failures.

OBJECTIVES

Identify the various types and grades of drillpipe used on Transocean rigs, and know how to determine the operating limits for each.

drillpipe RANGES

drillpipe comes in three ranges or lengths:

Basic Principles

Range API length (ft)

1 18 -22

2 27 - 32

3 38 - 45

GRADES

The grade of a pipe is commonly given by its minimum yield strength expressed in units of 1,000 pounds per square inch.

Grade D-55 has a minimum yield strength of 55,000 lb..../in2

Grade E-75 has a minimum yield strength of 75,000 lb..../in2

Grade X-95 has a minimum yield strength of 95,000 lb..../in2

Grade G-105 has a minimum yield strength of 105,000 lb..../in2

Grade S-135 has a minimum yield strength of 135,000 lb..../in2

Tensile strength of new pipe is the minimum yield strength x cross sectional area of pipe body

5” OD S-135 19.5 lbs..../ft has a cross section area of 5.2746 in2.

135,000 x 5.2746 = 712071 lbs..5.2746 in2

Nominal Size

Approximate Weight.

drillpipe TERMINOLOGY

Nominal Weight

Example5” OD E grade IEU NC50 drillpipe

BOXPIN Approximate Weight 20.89 lb..../ft

5”OD

Nominal Weight 19.5 lb..../ft

NC 26 - 23/8 IF or 27/8 SH

NC 31 - 27/8 IF or 31/2 SH

NC 38 - 31/2 IF, 31/2 WO or 41/2 SH

NC 40 - 4 FH

NC 46 - 4 IF, 41/2 XH or 4 WO

Some Examples of NC interchange

API AND THE NUMBERED CONNECTION (NC)

NC50 41/2 IF

5 XH

41/2 WO

V Thread Form

Flat Crest

RoundRoot

.065”

.038”

Designated as V-0.038R and mates with the V-0.065 thread form.

THE PIPE BODY IS OF SEAMLESS CONSTRUCTION

TOOL JOINTS AND UPSETS

EXTERNAL UPSET ( EU )

INTERNAL-EXTERNAL UPSET( IEU )

INTERNAL UPSET ( IU )

BOXPIN

Pins usually have 350 tapered shoulders Boxes usually have 180 tapered shoulders

HARDFACINGTONG AREA

TONG AREA

G 6 95 B E

SAMPLE MARKINGSAT BASE OF PIN.

1. TOOL JOINT MANUFACTURERS SYMBOL.

2. MONTH WELDED.

3. YEAR WELDED.

4. PIPE MANUFACTURERS SYMBOL.

5. drillpipe GRADE.

IDENTIFICATION

IDENTIFICATION

STANDARD WEIGHTGRADE X95 drillpipe

ONE GROOVE

STANDARD WEIGHTGRADE S135 drillpipe

THREE GROOVES

STANDARD WEIGHTGRADE G105 drillpipe

TWO GROOVES

HEAVY WEIGHTGRADE G105 drillpipe

ONE WIDE GROOVE

HEAVY WEIGHTGRADE E75 drillpipe

SLOT

STANDARD WEIGHTGRADE E75 drillpipe

NO MARKINGS

HEAVY WEIGHT HIGHSTRENGTH drillpipe

GROOVE

SLOT

STANDARD WEIGHT HIGHSTRENGTH drillpipe

SLOT

GROOVE

Stencil marking for permanent classification.

One punch mark = Premium Class

Two punch marks = Class 2

Three punch marks = Class 3

Tool Joint Condition Bands

Classification bands for drillpipe and tool joints

DRILLING TUBULAR CLASSIFICATION AND CONDITION

* Colour bands on the pipe are for presentation purposes only and do not represent a class or condition.

DRILLING TUBULAR FUNCTIONS

(1) Transmits rotary torque to the bit.

(2) Provides a conduit for circulating fluid to reach the bit.

The Drill String

The BHA

(1) Prevents buckling the drillpipe by keeping it in tension.

(2) Allows weight to be applied to the bit.

(3) Help stability of the bit.

(4) Minimise directional control problems.

DRILLING TUBULAR FATIGUE FAILURESdrillpipe Drill Collars

Near Slip Damage, Mashes or Dents

Near Internal Upsets

Near Last Engaged Thread Roots

DRILLING TUBULAR FATIGUE FAILURES

Pipe Bends Due To Hole Shape

Pipe Buckles Due To Excessive Weight Being

Applied

Collars Buckle When Weight Is Applied To Bit

HOW FATIGUE HAPPENS

Compression

Tension

DRILLING TUBULAR TYPES OF FATIGUE FAILURES

SLIP CUTS, MASHES AND DENTS CAN LEAD TO PREMATURE FAILURE

Notch in pipe focuses and accelerates fatigue

Fatigue crack starts at bottom of notch

Crack propagates through pipe until failure occurs

DRILLING TUBULAR TYPES OF FATIGUE FAILURES

INTERNAL UPSETS CAN LEAD TO PREMATURE FAILURE

0

0 8 16 24 32 40 48Distance From Box and Pin Ends (Inches)

20

40

60

80

100

%

Box End

Pin End

DRILLING TUBULAR TYPES OF FATIGUE FAILURES

BOTTOM HOLE ASSEMBLY CONNECTION FAILURE

Stress Concentrator Areas

SOLUTION

PROBLEM

Stress Relief Groove on Pin

Bare back on Box

Cold Rolling Thread Roots

DRILLING TUBULAR TYPES OF FATIGUE FAILURES

BOTTOM HOLE ASSEMBLY STIFFNESS RATIO

Selecting the correct combination of pipe sizes reduce stress levels.

Abrupt changes in OD and ID of collars.

5” OD x 3” ID

9” OD x 3” ID

8” OD x 3” ID

9” OD x 3” ID

For routine drilling or very low failure rate experience, keep (SR) below 5.5

For severe drilling or significant failure rate experience, keep (SR) below 3.5

DRILLING TUBULAR FATIGUEDrilling Mud Corrosion

Rate

Toughness Of The Material Bending

Strength Ratio

Cold Rolling Thread Roots

Stress Relief Features

BHA Design

Weight On Bit

Vibration

Sharp Transitions

DRILLING TUBULAR FAILURE

TENSION FAILURE

PIPE IS LITERALLY TORN APART WHEN

PULL EXCEEDS LOAD CAPACITY.

DRILLER STARTS PULLING ON PIPE.

TORSION FAILURE

EXCESSIVE TORQUE CAUSES PIN TO BE

SCREWED INTO BOX UNTIL IT FAILS IN

TENSION.

DRILLER STARTS ROTATING PIPE.

TENSION FAILURE TORSION FAILURE

Simultaneous Tension Reduces Torsional Yield

Strength in Pin Weak Connections

Simultaneous Torsion Reduces The drillpipe Tube

Tensile Capacity

DRILLING TUBULAR FAILURE

CONNECTION WASHOUTS

Helical Pathways in Thread Root.

Leak at Seal Area

DRILLING TUBULAR FAILURE

COLLAPSE AND BURST PRESSURE

EXTERNAL PRESSURE

EXTERNAL LOAD EXCEEDS TUBE YIELD STRENGTH AND

PIPE COLLAPSES

INTERNAL PRESSURE

INTERNAL LOAD EXCEEDS TUBE YIELD STRENGTH AND

PIPE SPLITS

MECHANICAL FAILURES

JARS BITS

SAFETY

VALVES

HOLE OPENERS

MUD

MOTORS

MWD

TOOLS

IBOP’s

SHOCK

SUBS

UNDER REAMERS

OTHERS

DRILLING TUBULAR FAILURE

SPLIT/BELLED BOX PIN STRETCHEXCESSIVE TORQUE

EXCESSIVE TORQUE

Thread Profile Gauge

Stretched Threads

EXCESSIVE TORQUE

Split

Box

Belled

Box

DRILLING TUBULAR CORROSION

OXYGEN: Causes rusting and pitting leading to washouts, twistoff’s and fatigue failure.

CARBON DIOXIDE: When dissolved in water forms a weak solution of Carbonic Acid that corrodes steel in the same manner as other acids. When present with Oxygen corrosion rate is higher than the individual corrosion rates.

HYDROGEN SULPHIDE: Is weaker and less corrosive than Carbonic Acid when dissolved in water. However a more significant problem is the effect known as Hydrogen Embrittlement or Sulphide Stress Cracking.

DISOLVED SALTS: Chlorides, Carbonates and Sulphates increase electrical conductivity of the drilling fluids. This increases electrochemical reactions and may result in higher corrosion rates.

ACIDS: Corrode metal by lowering the pH and dissolving protective films.

DRILLING COMPONENT FAILURES

WELDING

Hole Openers Underreamers Welded Blade Stabilisers

Rebuilt Tool Joints

SOME OF THE BAD PRACTICES THAT PEOPLE GET UP TO

Using Wrong Thread Protectors

Jacking Pipe With Tools Not Designed For Job ie.

(Stilson)

Using One Tong Instead Of Two For Make-up or

Breakout

Setting Slips Before Pipe Movement Stops

Riding Slips On Pipe

Using Rotary To Make-up or Breakout

Incorrect Stabbing (Hitting Shoulder or Rolling Pin

Into Box)

No Visual Inspection And Correct Doping Before

Making-up

Removing Thread Protectors Early

Not Spacing Pipe On Deck Correctly

Picking Pipe Up By Hooking Ends

DRILLING TUBULAR FAILURE PREVENTION

BALANCING AREAS THAT ARE WITHIN OUR CONTROL

FAILURE SCALE

Handling Inspecting

DesignEnvironment

Very Low

GOOD GOOD

FAILURE SCALE

Handling

Inspecting

Design

Environment

Very High

BAD