Horizontal Well Drill String Design

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

Example

5 OD E grade IEU NC50 drillpipe

BOX PIN Approximate Weight 20.89 lb..../ft

5OD

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 4

1/2 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.

THE PIPE BODY IS OF SEAMLESS CONSTRUCTION

TOOL JOINTS AND UPSETS

EXTERNAL UPSET ( EU )

INTERNAL-EXTERNAL UPSET

( IEU )

INTERNAL UPSET

( IU )

BOX PIN

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

HARDFACING TONG AREA

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.

IDENTIFICATION

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

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 FAILURES drillpipe 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


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


BOTTOM HOLE ASSEMBLY CONNECTION FAILURE

Stress Concentrator Areas

SOLUTION

PROBLEM

Stress Relief

Groove on Pin

Bare back on

Box

Cold Rolling Thread Roots


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 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

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


CONNECTION WASHOUTS

Helical Pathways in

Thread Root.

Leak at Seal Area


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

IBOPs

SHOCK

SUBS

UNDER

REAMERS

OTHERS


SPLIT/BELLED BOX PIN STRETCH EXCESSIVE

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, twistoffs 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

Design Environment

Very

Low

GOOD GOOD

FAILURE

SCALE

Handling

Inspecting

Design

Environment

Very

High

BAD

Documents

Horizontal Well Drill String Design