Horizontal Well Drill String Design

DRILLING PRACTICES Basic Drill String Standards

BASIC DRILL STRING STANDARDS OBJECTIVES Understand the basic principles of engineering mechanics that are involved in Drill String Standards and Drilling Tubular Failures. Identify the various types and grades of drillpipe used on Transocean rigs, and know how to determine the operating limits for each. 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.

Basic Principles drillpipe RANGES drillpipe comes in three ranges or lengths:

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

drillpipe TERMINOLOGY Example 5” OD E grade IEU NC50 drillpipe

Nominal Size 5”OD

Nominal Weight Nominal Weight 19.5 lb..../ft

Approximate Weight.

PIN

Approximate Weight 20.89 lb..../ft

BOX

API AND THE NUMBERED CONNECTION (NC) Some Examples of NC interchange 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 41/2 IF

NC50

5 XH 41/2 WO

Flat Crest .065”

V Thread Form

.038”

Round Root

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

TOOL JOINTS AND UPSETS THE PIPE BODY IS OF SEAMLESS CONSTRUCTION

EXTERNAL UPSET ( EU )

INTERNAL UPSET ( IU )

INTERNAL-EXTERNAL UPSET ( IEU )

Pins usually have 350 tapered shoulders

PIN

Boxes usually have 180 tapered shoulders

BOX

IDENTIFICATION

TONG AREA

HARDFACING

TONG AREA 1. TOOL JOINT MANUFACTURERS SYMBOL. 2. MONTH WELDED. G 6 95 B E SAMPLE MARKINGS AT BASE OF PIN.

3. YEAR WELDED. 4. PIPE MANUFACTURERS SYMBOL. 5. drillpipe GRADE.

IDENTIFICATION STANDARD WEIGHT GRADE X95 drillpipe

STANDARD WEIGHT GRADE S135 drillpipe

HEAVY WEIGHT GRADE E75 drillpipe

SLOT ONE GROOVE

STANDARD WEIGHT GRADE G105 drillpipe

NO MARKINGS

THREE GROOVES

GROOVE

TWO GROOVES

STANDARD WEIGHT GRADE E75 drillpipe

ONE WIDE GROOVE

HEAVY WEIGHT GRADE G105 drillpipe

SLOT

HEAVY WEIGHT HIGH STRENGTH drillpipe

SLOT

GROOVE

STANDARD WEIGHT HIGH STRENGTH drillpipe

DRILLING TUBULAR CLASSIFICATION AND CONDITION Tool Joint Condition Bands

Classification bands for drillpipe and tool joints

Stencil marking for permanent classification. One punch mark = Premium Class Two punch marks = Class 2 Three punch marks = Class 3 * Colour bands on the pipe are for presentation purposes only and do not represent a class or condition.

DRILLING TUBULAR FUNCTIONS The Drill String (1) Transmits rotary torque to the bit. (2) Provides a conduit for circulating fluid to reach the bit.

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 HOW FATIGUE HAPPENS

Compression

Tension

Pipe Bends Due To Hole Shape

Pipe Buckles Due To Excessive Weight Being Applied

Collars Buckle When Weight Is Applied To Bit

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

100 Box End

80

%

60 40 Pin End

20 0 0

8

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

48

DRILLING TUBULAR TYPES OF FATIGUE FAILURES BOTTOM HOLE ASSEMBLY CONNECTION FAILURE SOLUTION Stress Relief Groove on Pin Bare back on Box

PROBLEM Stress Concentrator Areas

Cold Rolling Thread Roots

DRILLING TUBULAR TYPES OF FATIGUE FAILURES BOTTOM HOLE ASSEMBLY STIFFNESS RATIO 8” OD x 3” ID

5” OD x 3” ID

Selecting the correct combination of pipe sizes reduce stress levels.

Abrupt changes in OD and ID of collars.

9” 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 Mud Corrosion Rate

Stress Relief Features

Toughness Of The Material

Bending Strength Ratio

Weight On Bit

Cold Rolling Thread Roots

BHA Design

DRILLING TUBULAR FATIGUE

Sharp Transitions Vibration

TENSION FAILURE

TORSION FAILURE DRILLING TUBULAR FAILURE Simultaneous Tension Reduces Torsional Yield Strength in Pin Weak Connections

DRILLER STARTS ROTATING PIPE.

DRILLER STARTS PULLING ON PIPE.

EXCESSIVE TORQUE CAUSES PIN TO BE SCREWED INTO BOX UNTIL IT FAILS IN TENSION.

PIPE IS LITERALLY TORN APART WHEN PULL EXCEEDS LOAD CAPACITY. Simultaneous Torsion Reduces The drillpipe Tube Tensile Capacity

TENSION FAILURE

TORSION FAILURE

DRILLING TUBULAR FAILURE CONNECTION WASHOUTS Leak at Seal Area

Helical Pathways in Thread Root.

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 MUD JARS

MOTORS

BITS

HOLE OPENERS

IBOP’s

SAFETY VALVES

OTHERS

MWD TOOLS SHOCK SUBS

UNDER REAMERS

DRILLING TUBULAR FAILURE EXCESSIVE TORQUE

SPLIT/BELLED BOX PIN STRETCH EXCESSIVE TORQUE

EXCESSIVE TORQUE

Split

Belled Thread Profile Gauge

Box Stretched Threads

Box

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

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

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.

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

Using Rotary To Make-up or Breakout

Not Spacing Pipe On Deck Correctly

Picking Pipe Up By Hooking Ends

Removing Thread Protectors Early

Using One Tong Instead Of Two For Make-up or Breakout Setting Slips Before Pipe Movement Stops

No Visual Inspection And Correct Doping Before Making-up

Riding Slips On Pipe

Incorrect Stabbing (Hitting Shoulder or Rolling Pin Into Box)

Jacking Pipe With Tools Not Designed For Job ie.(Stilson)

DRILLING TUBULAR FAILURE PREVENTION BALANCING AREAS THAT ARE WITHIN OUR CONTROL Very Low

GOOD

Environment Handling

FAILURE SCALE

Very High

BAD

Design Inspecting Environment Handling

FAILURE SCALE

Design Inspecting

GOOD