Horizontal Well Drill String Design

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Basic Drill String Standards

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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.

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drillpipe RANGES

drillpipe comes in three ranges or lengths:

Basic Principles

Range API length (ft)

1 18 -22

2 27 - 32

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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..

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Nominal Size

Approximate Weight. drillpipe TERMINOLOGY

Nominal Weight

Example

5” OD E grade IEU NC50 drillpipe

BOX

PIN

Approximate Weight 20.89

lb..../ft

5”OD

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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 Round Root .065” .038” Designated as V-0.038R and mates with the V-0.065 thread form.

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THE PIPE BODY IS OF SEAMLESS CONSTRUCTION TOOL JOINTS AND UPSETS

EXTERNAL UPSET ( EU )

INTERNAL-EXTERNAL UPSET

( IEU )

INTERNAL UPSET

( IU )

BOX

PIN

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HARDFACING

TONG AREA

G 6 95 B E SAMPLE MARKINGS AT BASE OF PIN.

1. TOOL JOINT MANUFACTURERS SYMBOL. 2. MONTH WELDED.

3. YEAR WELDED.

4. PIPE MANUFACTURERS SYMBOL. 5. drillpipe GRADE.

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IDENTIFICATION STANDARD WEIGHT GRADE X95 drillpipe ONE GROOVE STANDARD WEIGHT GRADE S135 drillpipe THREE GROOVES STANDARD WEIGHT GRADE G105 drillpipe TWO GROOVES HEAVY WEIGHT GRADE G105 drillpipe ONE WIDE GROOVE HEAVY WEIGHT GRADE E75 drillpipe

SLOT

STANDARD WEIGHT GRADE E75 drillpipe

NO MARKINGS

HEAVY WEIGHT HIGH STRENGTH drillpipe

GROOVE

SLOT

STANDARD WEIGHT HIGH STRENGTH drillpipe

SLOT

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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

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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.

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DRILLING TUBULAR FATIGUE FAILURES

drillpipe _{Drill Collars}

Near Slip Damage, Mashes or Dents

Near Internal Upsets

Near Last Engaged Thread Roots

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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

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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

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DRILLING TUBULAR TYPES OF FATIGUE FAILURES INTERNAL UPSETS CAN LEAD TO PREMATURE FAILURE

0

0 8 16 24 32 40 48

Distance From Box and Pin Ends (Inches) 20 40 60 80 100

%

Box End Pin End

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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

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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

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DRILLING TUBULAR FATIGUE Drilling 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

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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

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DRILLING TUBULAR FAILURE CONNECTION WASHOUTS

Helical Pathways in Thread Root. Leak at Seal Area

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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

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MECHANICAL FAILURES JARS _BITS SAFETY VALVES HOLE OPENERS MUD MOTORS MWD TOOLS IBOP’s SHOCK SUBS UNDER REAMERS OTHERS

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DRILLING TUBULAR FAILURE SPLIT/BELLED BOX PIN STRETCH EXCESSIVE

TORQUE

EXCESSIVE TORQUE

Thread Profile Gauge

Stretched Threads EXCESSIVE TORQUE Split Box Belled Box

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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.

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DRILLING COMPONENT FAILURES WELDING

Hole Openers Underreamers Welded Blade

Stabilisers

Rebuilt Tool Joints

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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

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DRILLING TUBULAR FAILURE PREVENTION BALANCING AREAS THAT ARE WITHIN OUR CONTROL

FAILURE SCALE Handling Inspecting Design Environment Very Low GOOD GOOD FAILURE SCALE Handling Inspecting Design Environment Very High BAD