2. Casing and Tubing

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Section 2

Casing and Tubing

Table of Contents

Introduction................................................................................................................................................2-3

Topic Areas ............................................................................................................................................ 2-3

Learning Objectives ...............................................................................................................................2-3

Unit A: Casing and Tubing Uses ...............................................................................................................2-3

Unit A Quiz ............................................................................................................................................ 2-4Unit B: Typical Casing Strings ..................................................................................................................2-5

Conductor Casing...................................................................................................................................2-5

Surface Casing........................................................................................................................................2-5

Protective Casing (Intermediate Casing)................................................................................................2-6

Production Casing ..................................................................................................................................2-6

Liners......................................................................................................................................................2-7

Tubing String..........................................................................................................................................2-8

Unit B Quiz ............................................................................................................................................ 2-9

Unit C: Casing and Tubing Threads ........................................................................................................ 2-10

Casing Threads.....................................................................................................................................2-10

Tubing Threads ....................................................................................................................................2-11

Thread Selection...................................................................................................................................2-12Make-Up Torque Selection ..................................................................................................................2-12

Thread Care .......................................................................................................................................... 2-13

Unit C Quiz .......................................................................................................................................... 2-14

Answers to Unit Quizzes ......................................................................................................................... 2-15

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Casing and Tubing

Use for Section Notes…

2 • 2 Cementing 1



Casing and Tubing

Introduction

For well operations to take place, lengths of

tubular goods are joined together and run down-

hole. Then, surface and downhole equipment

can be connected so that drilling and cementing

operations can proceed.

Due to the nature of our work, Halliburton

personnel must be familiar with basic drilling

operations. An understanding of the factorsinvolved in making up joints of casing, tubing,

and drill pipe will help you work more

effectively with customers as well as better

understand the ways in which Halliburton

equipment is used with these tubular goods.

Topic Areas

This section presents the following topics:

A. Casing and Tubing Uses

B. Couplings and Threads

C. Casing and Tubing Threads

Learning Objectives

Upon completion of this section, you should be

familiar with the

• Purpose and use of tubular goods

• Types of threads and how to select and care

for them

Unit A: Casing and Tubing Uses

Casing design involves three major steps:

1. Determining the sizes and lengths of casingstrings you will run

2. Calculating the type and size of loading

conditions

3. Choosing the weights and grades of casing

that will not fail when exposed to these

loads

This section will discuss the basics for

developing a casing program. An ideal casing

string design allows you to control common and

uncommon well conditions safely and

economically. Specifically, the casing program

should be appropriate for the geological

environment and allow safe well production.

Although it would be easy to choose a single

casing weight and grade to satisfy most well

conditions, you might be going to unnecessary

expense depending on the complexity of the

well.

A casing designer’s main job is to select the

weight and grades of casing that will be juststrong enough to withstand the loading

conditions of the well. Since casing is madefrom steel pipe, cost generally increases with

weight, but tensile strength and grade change

also affect prices. When selecting casing sizes

and final weights and grades, consider the

availability of tubular goods. You may not be

able to purchase certain types of casing in your

area. In extreme cases, you may have to base the

casing design on what is available; the main goal

is to simply make sure the specific string is

suitable for the well.To plan a well, you must first choose a

casing/bit system. When choosing this system,

you should consider

• Past experience with the area

• Geological factors

• Abnormal pressure

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Casing and Tubing

• Troublesome zones (such as salt) and

sloughing shale

• Lost circulation zones

Remember, the casing size and weight chosen

will determine casing inside diameter (ID). This,

in turn affects maximum bit diameter and limitsthe size of the next casing string.

The basic loading conditions on a casing or

tubing string that must be considered are

collapse, burst, and tension. All pipe designs

must carry a safety factor that considers the

uncertainty of the magnitude of these forces.

The Red Book ( Halliburton Cementing Tables)

lists collapse and burst (internal yield)

limitations for common pipe sizes and grades. In

addition, the Redbook provides limitations on

the tensile force (parallel to the axis of thecasing string) that is allowed for different pipe

sizes, grades, and coupling types. Tensile force

on the casing also has an effect upon the

collapse and burst values.

You may also encounter compression and

bending forces, which often occur in non-

vertical holes. The degree to which these forces

are exerted will also effect the burst and collapseresistance of the pipe. Another secondary

condition is load change during cementing due

to the placement of fluids of differing densities.

API bulletins, as well as the Redbook , contain

minimum burst, collapse, and tension casing

values. To use API’s monogram, casing

manufactures must use minimum standards set

by the API. Non-API casing is often

manufactured using the same standards, but for

critical wells, be sure that the material meets all

API standards.

Unit A Quiz

Fill in the blanks with one or more words to check your progress in Unit A.

1. The casing program should be appropriate for the __________________________ and allow safe

well production.

2. The casing size and weight chosen will determine casing ________________________.

3. The basic loading conditions on a casing or tubing string that must be considered are

______________, ________________, and _______________.

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Casing and Tubing

Unit B: Typical Casing Strings

In this unit, we will describe the purpose and use

of tubular goods used in a typical well.

Conductor Casing

Conductor Casing

Reservoir

Figure 2.1 - Conductor Casing

The conductor casing prevents washouts of

poorly consolidated surface soil and rock while

drilling the surface hole. Should the surface

erode, or become unstable, drilling rig stability

is compromised.

Conductor casing normally has a large diameter

(16 to 30 in.). It is either set with a spud rig or

driven to the point of refusal (150 to 250

blows/ft) with a drive or vibration hammer.

Setting depths is normally 90 to 150 ft and rarely

deeper that 300 ft.

Conductor casing allows you to install a diverter

system, and provides a flow line high enough to

allow mud return to steel mud pits while drilling

the surface hole. A blowout preventer (BOP)

may sit on the conductor casing above a large-

diameter (± 10 in.) vent pipe. If shallow

hydrocarbons are found, and the well flows, you

can close the BOP and divert flow away from

the rig. If such a shallow flow is encountered,

the well should not be completely shut in. It islikely, in most cases, that insufficient pipe is set

to prevent fluids or gas from breaking around

the outside of the conductor casing to surface. In

other words, the diverter system protects the rig

and personnel until the problem can be

corrected.

Surface Casing

The surface casing string (Fig. 2.2) is designed

to protect formations near the surface fromdeeper drilling conditions. The surface casing

string has several important functions. First, it

protects shallow freshwater sands from

contamination by drilling fluids and produced

fluids. Surface casing is cemented back to the

surface so freshwater zones will have a cement

sheath and a steel casing to protect them. Depth

and cement requirements are mandated by

regulatory agencies.

Surface casing allows you to drill to the next

casing seat. BOPs are nippled up on the surfacecasing; the well can be controlled if abnormal

conditions cause an inflow of formation fluid to

the wellbore. The surface casing is designed so

that the casing can be totally shut in using

surface equipment. When drilling into abnormal

pressure, casing seats must be able to withstand

increasing mud weights. Casing should be set

deep enough to prevent broaching to the surface.

Finally, surface casing supports all casing strings

run in the well.

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Casing and Tubing

Conductor

Casing

Surface

Casing

Cement

Reservoir

Conductor

Casing

Surface

Casing

Intermediate

Casing

Cement

Cement

Reservoir

Figure 2.2 - Surface Casing (Set inside theconductor casing)

Figure 2.3 - Protective Casing (Set insidethe surface casing and extending from total

depth to surface)

Protective Casing (IntermediateCasing)

One major advantage of protective casing is that

it allows underbalanced drilling of deeper

formations and isolates troublesome ones. It

allows you to isolate sloughing shales,

abnormally pressured saltwater flows, and

formations that contaminate the mud to prevent

interference during drilling operations

A protective (intermediate) casing string (Fig.

2.3) provides hole integrity during later drilling

operations. This intermediate string protects

formations behind it from high mud weights. It

also prevents drilling fluid contamination during

underbalanced drilling. Specifically, it performsthe functions covered in the following

paragraphs.

Production Casing

The production casing string (oil string) (Fig.

2.4) is set and cemented through the producing

zone and acts as a backup for the tubing string

during production. It is the primary string

responsible for isolating the desired production

interval(s). This string must be able to withstand

full wellhead shut-in pressure if the tubing leaks

or fails.

A protective casing string allows you to control

the well when encountering subsurface pressure

higher than the mud weight. If this takes place,

and fluid (or gas) enters the wellbore, drilling

fluid will be forced from the wellbore at surface.

The petroleum industry refers to this as a "kick".

In order to stop the formation-to-wellbore fluid

flow, the surface control equipment must be

closed or partially choked off. A positive surface

pressure will result. The protective casing isdesigned to withstand this pressure. Since it

covers low fracture gradient formations, it

maintains wellbore integrity during well-

kicking. Protective casing also allows you to

control the well if it is swabbed in, or if gas

purges all drilling fluids form the well.

After cementing the production casing, holes

(perforations) are made in the casing (andcement sheath) which allows fluid to enter the

wellbore. This is most often accomplished using

explosive charges ran on wireline units provided

by the logging service line.

When replacing the tubing or downhole tools

during well maintenance operations, you must

make sure the production casing will allow you

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Casing and Tubing

to kill the well (offset bottom hole pressure with

fluid hydrostatic head), circulate workover

fluids, and conduct some pressure testing.

Casing in general and production casing/liners

specifically, allow for a wellbore with consistent

known internal diameter. This is critical whenutilizing special downhole tools that require

these conditions. These tools are commonly

inserted into the casing during completion and

production operations in order to obtain

wellbore isolation at desired points.

In some areas, conditions may allow you to use

small diameter lines; in these instances,

production casing is set for well fluid

production. In other words, these are tubingless

completions – there is no backup string.

Conductor

Casing

SurfaceCasing

IntermediateCasing

ProductionCasing

Casing ShoeCement

Cement

Cement

Reservoir

Figure 2.4 - Production casing (Last fullstring of casing, set from total depth tosurface).

Liners

In the past, it was common to have severalstrings of casing in a deep well. All these strings

extended from the wellhead to different depths.

However, another method was devised to

accommodate varying well conditions. This

time- and money-saving method involves the

hanging of a casing string from the bottom of a

cemented casing string. These hanging casing

strings are called liners and they are used in

almost every deep well completion.

Four types of liners will be described briefly to

begin this section:

• Drilling (or protective) liners

• Production liners

• Stub liners

• Scab liners

Drilling Liners

A drilling liner (Fig. 2.5) is a string of casing

that is hung from another casing of a larger

diameter which has already been cemented

downhole. It is used to case off open holes sothat deeper drilling may be performed. A drilling

liner serves to

• help control water or gas production

• isolate lost-circulation zones

• isolate high-pressure zones.

A drilling liner is subject to the same design

conditions as protective casing, and it provides

the same protections. Multiple drilling liners

may be required. As with all liners, the top of

the casing does not extend to the surface, but is“hung off” at some point in the previous casing

string.

Figure 2.5 - Protective or Drilling liner (Setinside protective casing at current hole totaldepth, but does not extend to surface)

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Casing and Tubing

Production Liners Scab Liners

A production liner is a string of casing that is

hung from a drilling liner or casing in the

producing formation (Fig. 2.6). This type of

liner is then cemented and perforated like any

other completion string. It provides isolation and

support when casing has been set above the

production zone.

An unusual type of liner, a scab liner (Fig. 2.7)

is usually not cemented after it has been run

downhole and, therefore, it is retrievable. It has a

packoff on both ends and is used under the same

conditions as a stub liner.

Stub and scab liners can be set with part of their

weight on the liner below or hung uphole on

existing casing.

Conductor

Casing

Surface

Casing

Intermediate

Casing

Production

Liner

Casing ShoeCement

Cement

Cement

Reservoir

Production

Liner

Reservoir

Scab Liner

Figure 2.6 – Production liner (cemented in place but hangs from the bottom of theintermediate casing rather than extending to

the surface.

Figure 2.7 - Scab Liner

Tubing StringStub Liners

The tubing string gives produced fluids a flow

path to the surface and allows you to inject for

secondary recovery, storage, and disposal. By

increasing the size of this string, you can reduce

friction pressure and increase production or

injection rates. However, by increasing this

diameter, you must increase all other casing

sizes in the well. In other words, you must makesure the increased production/injection ratio

justifies the higher cost.

A stub liner (also called a tie-back liner) is

usually a short string of casing that provides an

upward extension for a drilling liner. It is run

when

• casing above the drilling liner has been

damaged in some way (by corrosion, etc.)

• a liner is leaking

• greater resistance is needed for other reasons

(abnormal pressure, etc.).

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Casing and Tubing

Unit B Quiz

Fill in the blanks with one or more words to check your progress in Unit B.

1. The first string in the well may be ___________ or ___________ casing. If the top soil is erodible,

then ___________ casing will be the first type run.

2. The conductor prevents ______________ under the rig.

3. Sometimes, conductor casing is set by simply _________________________ it into the ground.

However, if the soil is too hard, then the hole will be _____________ for it.

4. ____________ casing supports all casing strings run in the well.

5. Protective casing is also know as _____________________ casing.

6. A hanging casing string is called a ____________.

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Casing and Tubing

Unit C: Casing and Tubing Threads

Nearly all tubular goods used in completing a

well come in joints that vary from 30 to 40 ft in

length. Joints have threads machined into their

ends which serve to hold the string together.

Different types of tubular goods have threads

which differ in size, shape, and in the way they

seal and make up to hold pressure.

• Make-Up Torque selection

• Thread Care.

Casing Threads

Casing threads appear on both ends on the

outside of a joint of casing. Lengths of casing

are made up by using a collar (Fig. 2.9). A joint

screws into one end of the collar, while the next

joint screws into the other end. Most casing

threads are not upset, that is flared, as are many

tubing threads.

Cut on a taper, the threaded pin end and box endscrew together (Fig. 2.8). As the makeup torque

increases, the pin threads(which have less metal

than the box threads) begin to conform to the

box. Continued makeup causes additional

yielding until the pin end is wedged tightly intothe box. In this way, joints of tubular goods are

sealed together. Tensile loads and internal

pressures cannot easily force the separation of

the joined segments.

Figure 2.9 – Casing Joints and Collar

The most common threads (Fig. 2.10) in use

today for casing connections are:

• 8 round (8rd) thread has 8 rounded threads

per inchFigure 2.8 – Pin End and Box End

• Extreme line (Xline) thread has square

threads*

Since 1928, threads have been regulated by theAmerican Petroleum Institute (API). There are

five important areas of thread types, selection,

and care.

• Buttress thread has square threads.

• Casing Threads

• Tubing Threads

• Thread Selection

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Casing and Tubing

* Number of threads per inch varies basedupon the OD of the pipe.

Fig. 2.10 – Comparison of thread types.

Tubing Threads

The tubing or production string provides a flow path to the surface for produced fluids. Tubing is

not cemented into place as is casing. Therefore,

the threads on tubing joints and collars (Figure

2.11) are designed to withstand great tensile

loads and internal pressures. Like casing joints,

tubing has threads on both ends.Figure 2.11 – Tubing Joints and Collar

Two types of tubing threads (Figure 2.12) are

• External Upset (EU) – used in most wells

for added strength

•

Non-Upset – used in shallower wells and onthe surface.

Figure 2.12 – External and non-upset tubingthreads.




Casing and Tubing

Thread Selection

When working with the customer's casing,

tubing or drill pipe, it’s up to Halliburton

personnel to be sure that service equipment fits

the tubulars. Selection of the proper pin size(changeover from the casing/tubing to

Halliburton discharge piping) can sometimes be

difficult for the beginner.

In selecting the proper pin for casing, tubing or

drill pipe, the following information is needed:

• What type of thread is on the string?Figure 2.13- Caliper and ruler

• What is the outside diameter (OD) of the

pipe on the string? (For drill pipe you wouldneed to know the OD of the tool joint or

coupling).

Make-Up Torque SelectionThe type of thread varies depending upon which

type of pipe the customer has in the hole. The

OD tells you what size pin you need to connect

to the customer’s pipe.

To avoid stripping threads by applying too much

torque and to avoid loose connections by

applying too little torque, it is necessary to be

aware of optimum torque levels for the type of

tubular goods with which you’re working.

Charts, published by the API, are available to

help you.

For example, if you know the customer has 5 ½

inch 8rd casing, your equipment should also

have an OD of 5 ½ inches and 8 round threads

per inch.

As an example, let’s assume that you want to

make up a float collar on the customer’s casing.

The casing has this stamp: 5 ½ in. casing,

15.5lb/ft, J-55, grade, 8rd, long thread.

On location, check the specifications, which arestenciled on the side of the joints. If the joints

are not marked, you’ll need a caliper tool (Fig.

2.13) and ruler to identify pin dimensions.

To use the make-up torque charts, you need to

know all the information provided by this stamp.

The stamp tells you that the casing has:

• An outside diameter (OD) of 5 ½ inches

• 15.5 lb/ft nominal weight, threads and

coupling

• J-55 grade

• 8 round threads per inch

• long thread.




Casing and Tubing

Torque, ft-lb

Short Thread Long ThreadSizeOutside

Diameterin.

NominalWeight,Threads

andCouplinglb per ft Grade Optimum Minimum Maximum Optimum Minimum Maximum

5 ½ 14.00

14.0015.5017.00

14.0015.5017.00

H-40

J-55J-55J-55

K-55K-55K-55

1300

172020202290

189022202520

980

129015201720

142016701890

1630

215025302860

236027803150

__

__21702470

__23902720

__

16301850

17902040 __

__

__27103090

__29903400

6 5/8 20.00

20.0024.00

20.0024.00

H-40

J-55J-55

K-55K-55

1840

24503140

26703420

1380

18402360

20002570

__

30603930

33404280

__

26603400

29003720

__

20002550

21802790

__

33304250

36304650

Using this information, you can look up the

optimum, minimum, and maximum torque to be

applied when making connections with this

casing. To do this,

• find the chart for casing and your thread

size.

• The first column of this chart is labeled

“Size:Outside Diameter.” Find the columnfor 5 ½ in. OD casing.

• Columns 2 and 3 are labeled “Nominal

Weight, Threads and Coupling lb per ft” and

“Grade.” Find the row for the casing you’re

working with (15.5 lb/ft and Grade J-55).

• Columns 7, 8 and 9 are labeled “Long

Thread,” and Optimum,” Minimum,” and

“Maximum” torque levels. For the casing

you’re working with, these levels are 2170,

1630, 2710 ft-lb, respectively. Thus, proper

torque for this casing is between 1630 and2710 ft-lb, and 2170 ft-lb is the best torque

to apply.

Thread Care

When working with both surfaces and down-

hole equipment, you should be careful to protectthe threads. Because of the tremendous pressure

this equipment is designed to withstand, taking

care of thread could mean the prevention of a

serious accident and injury.

Before taking a piece of equipment to location,

you should

• Carefully remove the thread protectors.

• Inspect the threads for damage (sometimes

diesel fuel or a solvent will be needed to

remove grease to inspect for damage). Look

for galling, cracking, or cross-threading. If

you’re not sure, check with your supervisor.

• Put on safety glasses and clean the threadsusing a wire brush.

• If the threads will be chemically welded

(with Halliburton Weld-A), bentonite gel

will be needed along with a wire brush to

remove all grease from the threads on the

equipment as well as on the casing. Check to

see that all welds have met established API

codes.




Casing and Tubing

After a piece of equipment has been inspected,

equal care should be taken in its use:

• Never allow threads to hit metal or hard

objects.

• Never drop or throw equipment.

• Be aware of proper torque when making up

a piece of equipment.

• Place wrenches close to the threads but not

on them.

After you’ve finished using the equipment,

reinspect it for damage. Be sure to clean the

thread protectors and carefully reattach them to

the equipment.

Remember, if you have a question about the

condition of a thread, ask a supervisor. One blown out pin could not only cause an accident,

but could also leave you with a workstring full

of cement.

Unit C Quiz

Fill in the blanks with one or more words to check your progress in Unit C.

1. Threads have been regulated by the _______________ for over 50 years.

2. As a connection is screwed together, the pin threads begin to ______________ to the box threads.

Eventually, the pin end is ________ tightly into the box, which produces a __________ against

internal pressure.

3. Both the ____________ and____________ types of casing threads are square-shaped.

4. The two main questions you need to answer when choosing the proper pin size for casing or tubing

are: What is the type of ______________ on the string, and what is the ______________ of the pipe

on the string?

5. When inspecting threads, you should look for _________________, __________________, and

___________________.




Casing and Tubing

Answers to Unit Quizzes

Items from Unit A Quiz Refer toPage

1. geological environment 2-3

2. inside diameter (ID) 2-4

3. collapse, burst, tension 2-4

Items from Unit B Quiz Refer toPage

1. conductor, surface, conductor 2-5,6

2. washout (or erosion) 2-5

3. driven, drilled 2-5

4. Surface 2-6

5. intermediate 2-6

6. liner 2-8

Items from Unit C Quiz Refer toPage

1. API 2-10

2. conform, wedged, seal 2-10

3. buttress, extreme line 2-10

4. thread, outside diameter 2-12

5. galling, cracking, cross-threading 2-13




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