Casing/Tubing design manual october 2005 Chevron

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5.5.1 Internal Profile

In applications involving high flow rates, for example in high-volume gas wells,

the contour of the tube should be a smooth as possible. Most proprietary

connection designs attempt to maintain a smooth bore. It should be emphasized,

however, that for very high flow rates even a small change in flow diameter can

induce turbulence and possible wear or corrosion.

5.5.2 Large OD Connection Backout Torque

Large OD connection backout torque may be reduced because of trapped dope,

especially on premium connections. Some connections may be affected more

than others (ANJO, Hy 511). Special preparation may be required (dry box or

special doping for the box on Hydril

large OD connections).

5.6 Chevron-Approved Connections

5.6.1 Chevron Connection Classification

The classification of Chevron-approved connections is based on the reliability of

connections in terms of their sealing ability and structural strength. Chevron-

approved connections are grouped into five sealing classes and four structural

classes, or a 5 x 4 matrix connection classification (e.g., Class x-x), through an

evaluation of connection design, connection test data, connection field

experience data, and a judgment as to roughly equivalent connection designs.

The first number in the connection classification designation represents the

sealing class and the second number indicates the structural class. For example,

a Class 1-1 connection refers to a connection of sealing class 1 and structural

class 1, which is the most reliable connection, suitable for the most severe

services. A connection of Class 5-4 refers to a connection of sealing class 5 and

structural class 4, which is the lowest-rated connection. Class 5-4 connections

should only be used in low-pressure, routine wells.

Table 5-1 illustrates the 5 x 4 classification matrix for standardized Chevron-

approved casing connections. Table 5-2 presents the 5 x 4 classification matrix

of standardized Chevron-approved tubing connections.

Table 5-1. Chevron Standardized Casing Connections

Structural Class Casing Connection

Classification

1 2 3 4

1 * *

Sealing

Class

2 Hy 563 Hunting SL-

Apex

VAM TOP

VAM ACE

Hy 533

Tenaris

NK3SB

Tenaris

AM52B

Hy SLX

GP HDL

GP STL

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Structural Class Casing Connection

Classification

1 2 3 4

JFE KSBEAR

GP TC-II

3 Hunting SL-

VAM NEW

Hy 523

Tenaris Blue

Tenaris AMS

Hunting SL-

VAM SLIJ-II

GP ANJO

Hy 513

Hunting FSL

VAM FJL

4 Hunting

BOSS

VAM Dino

GP ATS-E

Hy 521

Tenaris ER

API BTC-RS

Hy 511

DQ QT

Vetco RL4

APILTC

APILTC-RS

API STC-RS

5 API BTC API STC

* Sealing class 1 connection is not qualified. Contact Chevron ETC for a case-by-

case recommendation.

Table 5-2. Chevron Standardized Tubing Connections

Structural Class Casing Connection

Classification

1 2 3 4

1 * VAM TOP

Tenaris

NK3SB

Hy 563

Hunting SL-

Apex

Hunting

TSHD

VAM ACE

Tenaris

AM52B

Hy 533

Hy PH6

GP TC-11

GP RTS6

JFE KSBEAR

JFE Fox

GP HDL

GP STL

3 VAM NEW

Tenaris Blue

Tenaris AMS

Hy 523

Hy CS

Hunting

TSHP

GT RTS8

Hy 513

Hunting FSL

VAM FJL

Hunting SL-

APIEU-RS

Hy 511

APINU-RS

APIIJ

Sealing

Class

5 APIEU APINU

* Class 1-1 connection is not qualified. Contact Chevron ETC personnel for a

case-by-case recommendation.

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October 2005

The selection of threaded casing and tubing connections for an engineering

application is a two-part process consisting of the following:

1. Determine the required classes of connections based on well condition levels

of application

2. Select a connection from the required classes of connections in the 5 x 4

matrix connection classification

5.6.2 Well Conditions for Connection

Selection

The well conditions are categorized by well pressure level, H

S level, tubular

length, well proximity, wellbore build/turn rate, and formation loading to determine

the use of connection classes for different well conditions. The more severe the

well condition level, the higher the required connection class.

Table 5-3 is designed to help you determine the required connection sealing

class according to pressure level, H

S level, and well proximity.

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Table 5-3. Chevron Connection Sealing Classes

Well

Conditions

A B C D E F

NACE No Yes No Yes Yes Yes

High H

S No No No Yes No Yes

Proximity No No Yes No Yes Yes

Tubular

Pressure

Connection Sealing

Class

0 to 2,500 psi 5 5 5 4 4 3

2,500 to 5,000

psi

5 4 4 3 3 2

5,000 to

10,000psi

4 4 3 2 2 1

10,000 to

15,000 psi

3 3 2 1 1 1

Above 15,000

psi

3 2 1 1 1 1

National Association of Corrosion Engineers (NACE)—Yes, if partial pressure

S in the gas phase exceeds 0.05 psi.

High NACE—Yes, if H

S exceeds 100 times of NACE.

Proximity—Yes, if the well is near other wells or in an expensive/environmentally-

sensitive area.

Table 5-3 poses three well conditions that must be addressed to determine the

required connection sealing class for a well application:

1. NACE

2. High H

3. Proximity

Find the column in Table 5-3 that corresponds to the three answers and locate

the connection sealing class in the appropriate tubular-pressure level row. The

connection sealing class determined from Table 5-3 represents the minimum

class recommended for the indicated application. All connections in the minimum

and better classes are candidates for purchase and use in the well. Local

management may approve use of a lesser connection class based on local

conditions and justifying data. Three “yes” answers define the most critical

service and three “no” answers define routine service.

No distinction is drawn between tubing, production casing, and liner versus

intermediate casing and drilling liners or surface casing. The tubular-pressure

level and the well conditions shown in Table 5-3, account for differences in well-

service level. The service levels apply to segments of individual strings, rather

than to a complete well. For example, a deep well expected to produce at high

S may have a production casing with the well condition D, and an intermediate

casing with the well condition B, and a surface casing with well condition A.

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October 2005

NACE—questions if well conditions meet the NACE MR 01-175 definition of sour

service. The answer to this question is “yes” if the anticipated service has a

partial pressure of H

S in the gas phase greater than 0.05 psi and the maximum

pressure exceeds approximately 200 psi. Partial pressure H

S is computed as

the product of:

• Parts-per-million H

S (mol percent H

S expressed as ppm)

• The maximum anticipated total pressure (psia)

• 1/one million

For example, 10-ppm H

S is not sour service at 1,000-psi maximum pressure:

Partial pressure H

S = 10 ppm (1,000 psi)/1,000,000 = 0.01 psi < 0.05 psi

However, at 15,000-psi maximum pressure, 10-ppm H

S is sour service and the

answer is “yes”:

Partial pressure H

S = 10 ppm (15,000 psi)/1,000,000 = 0.15 psi > 0.05 psi

High H

S—refers to the partial pressure of H

S. If the partial pressure of H

S is

greater than 5 psi (100 times the NACE limiting value), then the answer to this

question is “yes.” If the partial pressure of H

S is not greater than 5 psi, then the

answer is “no.” For a high concentration of H

S, it is appropriate to use a more

reliable connection.

Proximity—refers to the nearness to other wells, as well as to environmentally

sensitive or populated areas. The term “environmentally sensitive” refers to

situations in which an extra margin of environmental concern may be

appropriate. If a well mishap would endanger either a sensitive or populated area

or the investment in other wells, the answer to this question is “yes.” If not, the

answer is “no.” The use of a more reliable connection is appropriate if the answer

is “yes.”

The tubular pressure level indicated in Table 5-3 refers to the differential

pressure load used in tubular design (i.e., the difference between internal

pressure and external pressure under the design conditions which the pipe and

connection must carry). For drilling casing near the surface, this load usually

decreases from the surface downward. Near bottom, where collapse loading

dominates, the differential pressure load increases with depth.

For a deep intermediate casing string, the changing pressure could result in a

lesser class sealing of connection at mid-depth compared to top and bottom

depth. The pressure load is usually burst-dominated for production casing and

tubing, and is nearly constant at the maximum-anticipated surface shut-in

pressure. The pressure load may not be constant for unusual completion

practices or unusual completion tools. For a liner, the pressure load is clearly

different from surface pressure. In any case, the pressure levels shown in Table

5-3 do not contain the design factors, which are usually applied to loads to obtain

required ratings.

Table 5-4 determines the required connection structural class according to

tubular length, wellbore build/turn rate, and formation loading.

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Table 5-4. Chevron Connection Structural Classes

Well Conditions A B C D E F

Directional Well No Yes No No Yes Yes

High-Rate

Directional Well

No No Yes No No Yes

Formation Loading No No No Yes Yes Yes

Tubular Length (Below Point of

Interest)

Connection

Structural Class

0 to 5,000 ft 4 4 3 3 2 2

5,000 to 10,000 ft 4 3 3 2 2 2

10,000 to 15,000 ft 3 3 2 2 2 1

15,000 to 20,000 ft 3 2 2 2 1 1

Above 20,000 ft 2 2 1 1 1 1

Directional well—Yes, if the build/turn rate exceeds 5 deg/100 ft.

High-rate directional well—Yes, if the build/turn rate exceeds 10 deg/100 ft.

Formation loading—Yes, if there is formation compaction or a salt zone.

For large size casing (above 10¾”) used in high rate directional well, contact

Chevron tubular experts.

Table 5-4 displays the well-service level that must be addressed to determine the

required connection structural class for a well application:

• Directional Well

• High-Rate Directional Well

• Formation Loading.

Find the column in

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Table 5-4Table 5-4 that corresponds to the three answers, then locate the

connection structural class in the appropriate tubular-length level row. The

determined connection structural class specified in Table 5-4 represents the

minimum recommended for the indicated well application. All connections in the

minimum and better classes are candidates for purchase and use in the well.

Local management may approve use of a lesser connection class based on local

conditions and justifying data. Three “yes” answers define the most critical

service and three “no” answers define routine service.

No distinction is drawn between tubing, production casing, and liner versus

intermediate casing and drilling liners or surface casing. The tubular-length level

and well conditions in

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October 2005

Table 5-4Table 5-4 account for differences in services for these various uses.

The service levels apply to segments of individual strings, rather than a complete

well. For example, the surface casing in a directional well will usually be set in

vertical wellbore and will not be exposed to the build/turn rate wellbore condition.

Further, an extended-reach directional well could have production casing with a

well condition C, intermediate casing with a well condition B, and surface casing

with a well condition A.

Directional Well—questions whether or not the well is a directional well with a

build/turn rate that exceeds 5 deg/100 ft. Because the tubulars running in

directional wells are subject to more severe torque, drag, and bending than

tubular running in a vertical well, the reliability rating for connections will be

higher for directional wells than for vertical wells. The answer is “yes” if the

tubulars are setting in or running through the build/turn section of a directional

well with the build/turn rate exceeding 5 deg/100 ft.

High-Rate Directional Wellbore—also refers to the build/turn rate of directional

wells. If the tubulars are setting in or running through the build/turn section of a

directional well in which the build/turn rate exceeds 10 deg/100 ft, then the

answer to this question is “yes.”

Formation Loading—refers to unusual formation loading because of formation

compaction or flowing salt formation. Formation loading conditions require

connections with higher structural strength classifications. The answer to this

question is “yes” if the tubulars are setting through such formations.

The tubular length shown in

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Table 5-4Table 5-4 represents the tubular length below the point of interest

(related to tubular tension load), not necessarily the tubular setting depth nor the

well depth. For a liner, the tubular length will be short although it can be set at a

deep depth in the well. For a long tubular string, a lesser structural class of

connection may be used for the bottom segment of the string when compared to

the top segment of the string. This is because the tubular length of the bottom

segment of the string is less than the top segment of the string.

5.6.3 Connection Selection Example

For this example scenario, select an appropriate connection for a 9-5/8-in.

protective casing string set to 7,000 ft depth in an offshore directional well (build

rate 6 deg/100 ft). Other well conditions include the following:

• Maximum anticipated surface pressure 7,000 psi

• No H

• No formation loading from formation compaction or salt zone

5.6.3.1 Step 1–Use Table 5-3 to Determine the Required

Connection Sealing Class

The well condition is “C” for the determination of required connection sealing

class because of the answers generated in response to the three questions

posed in Table 5-3.

• No to “NACE”

• No to “High H

S”

• Yes to “Proximity” for an offshore well

The required connection sealing class is then “3” because the maximum

anticipated surface pressure of 7,000 psi is between 5,000 to 10,000 psi.

5.6.3.2 Step 2–Use Table 5-4 to Determine the Required

Structural Class

The well condition is “B” for the determination of required connection structural

class because of the answers generated in response to the three questions

posed in

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Table 5-4Table 5-4.

• Yes to “Directional Well”

• No to “High-Rate Directional Well”

• No to “Formation Loading”

The required connection structural class is then “3” because the 7,000-ft string

length is between 5,000 ft to 10,000 ft.

5.6.3.3 Step 3–Use Table 5-1 to Select the Possible

Casing Connections

The required connection is a Class 3-3 connection and any Class 3-3 connection

in Table 5-1Table 5-1 can be selected for this application, such as Hunting SL-SF

connection or VAM SLIJ-II connection.

Any connection with a higher class rating, such as connections in Class 3-2 or

Class 2-3 is also qualified for this 9-5/8 in. protective casing.