The document provides an overview of wellhead components and their functions. It discusses the key parts of a wellhead including casing head housing, casing head spool, tubing head spool, flanges, seals, and hangers. The document also outlines API specification 6A for wellheads and the objectives of the course which are to familiarize students with wellhead components, selection criteria, API standards, and installation/use considerations.

1. INTEGRATED
DRILLING
SERVICES
IDS
Wellheads

2.  Wellhead definition
 Wellhead Components
– Flanges, ring gasket and outlets
– Casing head housing
– Casing head spool
– Casing hanger
– Primary and secondary seals
– Tubing head spool
 Wellhead Specification as per API 6A
 Wellhead Running procedure
 Wellheads for special application
Course Agenda

3. Module Objectives
At the end of this presentation YOU will:
 Be familiar with Wellhead components
 Be able to select an appropriate type of Wellhead system for a
standard land / jack-up operation
 Be familiar with API Specification 6A
 Be aware of a some of the issues with installation and use of
surface wellheads
Wellheads

4. What do we find ?
Casing Suspension
Equipment ( 1 )
Tubing Suspension
Equipment ( 2 )
Flow Control
Equipment ( 3/4/5 )
A Section
B Section
C Section
Xmas Tree

5. The wellhead is the surface foundation on which the well is built up during
the drilling operations and is the base for the x-mas tree for production
operations.
What is a wellhead ?

6. Objectives of the wellhead:
 Withstand tensile loads of suspended tubular
 Provide a pressure sealing capability
 ISOLATE the well from the external environment
 ISOLATE between casings and downhole formations
 MAINTAIN PRESSURE during well control operations, well testing or shut in
periods.
 Those functionalities must be achieved during the life of the
well (Drilling, Production, Workover, Suspension and Abandonment)

7. What are the main components ?
Casing Head Housing
Casing Head Spool
Tubing Head Spool
Xmas Tree
Wellhead

8. Working pressure of 10000 psi and 3 1/16 bore
What does this mean ?
a 3-1/16 , 10 000 flange
Flanges
A protruding rim with holes to accept bolts and having a sealing mechanism used to join
pressure containing equipment.
There are two types of flanges (ring grooves):
API 6B - 2,000, 3000, 5,000 psi (up to 11”)
API 6BX - 5,000 (from 13 5/8”) to 20,000 psi

9. Ring Gaskets
TYPE 6B
RING GASKETS
Type R (oval or octagon
shape)
Type BX
(square cross section with
tapered edges)
TYPE 6BX
FLANGES
Type RX
(octagon asymmetrical
shape)
Notes: BX and RX rings are pressure energized, meaning that pressure, in case of leaking, helps to
improve the sealing. RX rings from sizes 82 through 91have pressure equalizing hole.
Ring gasket shall not be reused.
Ring gaskets are made of a softer material than the flange body; therefore, they deform after being
placed and tightened with the flange bolts. This results in a better seal.

10. Flanges and Ring Gaskets
type R & RX type BX
Standoff No Standoff

11. Standard Flange Sizes
inches millimeters
1 13/16 46
2 1/16 52
2 9/16 65
3 1/16 or 3 1/8 78 or 79
4 1/16 103
5 1/8 130
7 1/16 179
9 228
11 279
13 5/8 346
16 ¾ 425
18 ¾ 476
20 ¾ 527
21 ¼ 540
26 ¾ 680
30 762
Notes:
When converting to millimeters they are rounded to the nearest millimeter.
For flanges, the nominal flange size is equal to the bore size of the flange, but for wellhead
sections the bore size is slightly smaller.
Bore sizes for wellheads can be found in Table 10.34 of API Spec 6A.
What are the common flange sizes used in wellhead equipment ?

12. Casing head Housing
It is the lowest part of the wellhead assembly and almost
always connected to surface casing. It support subsequent
drilling wellhead and completion string.
Its main functions are:
 Provides for attachment to surface casing string
 Supports BOP during drilling operation
 Provides for suspending and packing of the next casing string
 Provides outlets for annular access
 Provides for testing BOP while drilling

13. Casing Head Housing (CHH) types
The welding must be tested through
“Test port” located between the two
welding. Not that the plug needs to be
removed before the welding.
Although safer, threaded CHH requires to have the
uppermost casing thread at precise depth.
If the surface casing has to be set off depth (fill on
bottom, stuck casing), slip-on CHH has to used.
They can be installed faster than a slip-on weld type.
They can be re-installed or removed. This allows to use
it as a temporary tool while drilling the intermediate hole.
Slip on
Threaded
Sliplock

15. Casing Head Housing - Description
Slip-on weld or threaded
bottom connection
Test port
Side outlets threaded or
studded
Top connection flanged (standard)
Ring groove
Landing area for
Casing Hanger

16. CHH - Type of Outlets
Threaded outlet*
Flanged Clamp hub
Studded flange
*Usually low pressure and cost

17. The load acting on the the Casing Head Housing might be high (in case of deep well for
instance). In this case a base plate is used to distribute the load and to increase the stability
of the wellhead.
The base plate sets at the bottom of the cellar.
Base Plate

18. Casing hanger
The objectives of the casing hangers are to:
 Suspends intermediate or production casing string
 Centers the casing string in the head (or spool)
 Seals off the casing annulus (It is the primary seal )
There are many types of hangers. Two major types of casing hangers : slip type hanger
(wraparound casing slips) and mandrel type hanger. Wraparound casing can be set
without removing BOP under certain conditions.

19. Slip type hangers (examples)
Wraparound casing slips with sealing capability provided by casing
load
Dual slips distribute casing load to reduce casing deflection at high
loads.
Use to obtain seal independent of the casing load (when no casing
load available to energize the seal). Elastomer seal are
mechanically activated by cap screws
Casing hanger has an independent slip and seal assembly. The
seal is installed when the casing cut off.

20. Casing head Spool
Its main functions are:
 Seals off (packs off) previous string
 Provides for suspending and packing of the next casing string
 Provides support for well control equipment (BOP Stack)
 Provides outlets for annular access
 Provides for testing BOP while drilling
It has a top bowl to accommodate the next casing hanger. It has a
bottom bowl with a pack-off seal (or bushing) and a flange for
mounting it up on the top of the casing head housing or previous
casing head spool. Multiple casings spools can be stacked to
hang intermediate or production casing strings.

21. Casing Head Spools - Description
Pack Off (or Secondary Seal) is designed to
fit around OD of current casing.
Test port
Side outlets can be threaded/ studded / flanged
(threaded not common).
The top flange has a different size
and rating than the bottom flange.
Landing area for
Casing Hanger
The bottom flange is compatible with the
previous casing head or casing spool flange.
The bottom flange includes a test port (with a
non-return valve) allowing to test between
the ring gasket, primary and secondary seal.
Some CHS seal includes a port that allows
injection of sealant in order to energize or re-
energize the secondary seal (this feature is not
include in this picture).

22. Primary and Secondary Seal
Secondary Seals
Primary Seals
Therefore, there are two separate
barriers which prevent pressure from
communicating with the environment
outside the wellhead and up with the
subsequent annulus.
This figure illustrates pack-off type secondary
seals. Some of these secondary seals require
plastic injection to re-energize or energize them.

23. Spacer Spool & Adapter Spool
The DSA (Double Studded Adapter) or the
adapter spool. They are usually used to
adapt between different flange end
connections that would otherwise not
connect. Usually the two sides are
different in size and/or pressure rating.
Spacer Spool or also called Mud Cross. It
is a unit of equipment used with Blowout
Preventer to space pieces of equipment
apart and provide outlets to attach lines
extending to Choke and Kill Manifolds.

24. Tubing head Spool
Its main functions are:
 Seals off (packs off) the production casing
 Provides for suspending and packing of the completion string
 Provides support for well control equipment (BOP Stack)
 Provides outlets for annular access
It is the top spool on a surface wellhead assembly. It is installed
after the last casing string to provide shoulder to support the
tubing string and a seal bore for the tubing hanger or production .
When the well is completed, the tree is installed on top of the
tubing head.

25. Tubing Head Spools (THS) - Description
Pack Off is designed to fit around OD of the production
casing.
Side outlets can be threaded/ studded / flanged (threaded not
common).
The top flange has a different size and rating than the bottom
flange. A tubing hanger lock down bolts system is included.
The bottom flange is compatible with the previous casing
spool flange.
The bottom flange includes a test port (with a non-return
valve) allowing to test between the ring gasket, primary and
secondary seal.
Some THS seal includes a port that allows injection of sealant
in order to energize or re-energize the secondary seal (this
feature is not include in this picture).
The top bowl provides support for the tubing hanger.

26. Tubing Hangers
There are many type of the tubing hanger. Most of the tubing
hanger are mandrel type.
The top thread allows the connection when setting or
removing the completion string.
Most of them have a primary and secondary seals.
The internal body is threaded to accommodate a back
pressure valve (BPV).
The BPV allows to shut-in the well when removing or
installing the BOPs / X-Mas tree.
The bottom thread allow the connection with the completion
string.

27. Wear Bushing
• Run and set into top bowl to protect wellhead
from wear during drilling operation.
• Lock screws tightened to contact wear bushing
can be used if casing head has this feature.
• Most wellhead from major manufacturers
incorporate the wear bushing lock assembly into
the body of the spool using a “J” slot system.
• It needs to be remove before running the next
casing string.
When wear bushing is not used

28. Wellhead Standards: API 6A
Covers Wellhead and Xmas Tree equipment
 Mainly manufacture and specification.
 Does not really cover, application, installation or operational aspects.
 Guidelines on selection of equipment and quality assurance ( Product
Specification Levels – PSL).
Temperature and Pressure Ratings
Materials
 Standard & H2S / CO2 Conditions (NACE standard)
Requirements for welding on wellhead equipment
Quality control, marking of equipment, storing and shipping.
Details specific requirements for the different components.

29. Pressure Ratings of Equipment
Equipment shall be designed to operate in only the following maximum rated working
pressure:

30. Table 4.2 of API Spec. 6A illustrates the temperature ratings classification for wellhead
components.
Temperature Rating

31. Material Specifications
The material specification is dependent on the concentration of H2S and CO2 in
the produced fluid.

32. Some Material definition

33. Corrosion from API 6A

34. Product Specification Levels (PSL)
The PSL indicates the service conditions for which the wellhead may be used. API has
defined four PSLs for wellhead equipment (PSL1-4). The four PSL designations define
different levels of technical requirements.
It defines also specification for quality control of equipment.
The more critical the application (pressure, fluid composition and close proximity) of
the wellhead the higher the PSL level is.
A higher PSL level requires a greater level of testing and the traceability of the
materials.
Appendix A of the specification has a flow chart which helps define the PSL level
required.

35. API Spec 6A flow chart to determine PSL level.

36. CHH, CHS & THS Identification – API 6A

37. How to order Casing Hanger
Casing hangers are ordered together with the wellhead sections since not
all hangers are suitable for all sections.
The following details of the application should be discussed in the
planning phase with the supplier to obtain the proper hanger:
• Casing size, weight and grade
• Casing setting depth
• Expected tension of the top joint
• Surface temperature
• Composition of fluids to which it will be exposed

38. Well Head for Special Applications
1. Compact spool systems
2. Subsea wellheads
3. Splitter wellheads where conductor slots are limited
4. Dual Completion

39. Compact Wellheads
Advantages (Vs conventional Wellhead):
 The BOP Stack can be left in place until the installation
of Xmas tree.
 It saves rig time.
 Reduction of flanged connections.
Disadvantages (Vs conventional wellhead):
 Cost
 Support service is required
 Require contingency equipment

40. Subsea Wellheads
• Build on single unit. Concept of
compact wellheads was derived
from subsea wellheads
• Each casing string is landed on
top of the previous one

41. Subsea Wellheads

42. Splitter Wellheads

43. Dual tubing hanger

45. Intermediate – 13 3/8” 5000 ft – Expected LOT = 17.5 ppg
Conductor 30” X 2 jts
Surface - 20” – 1500 ft. Expected LOT = 14.5 ppg
Production Casing 9 5/8” – 9000 ft.
7” Liner – 8500 - 10,000 ft.
C95 38# New Vam
ABC Productive Sands – from 9300 to 1000 ft. Estimated formation pressure = 7500 psi. H2S
content = 0 ppm. BHT = 180oF.
Exercise # Group 1
Discussion Groups
1) Design a basic wellhead and Tree for the following development well.
5 ½” Production Tubing
The formation between 5000 and 9000 ft is a highly compacted shale with sand
stringers between 7000 and 8000 ft. These stringers could contain pockets of gas.
The mud weight for this section will start at 14.0 ppg and will be increased
progressively to 15.5 ppg.
The formation between 1500 and 5000 ft is a plastic clay. The mud weight for this
section will start at 9.0 ppg and will be increased progressively to 10.5 ppg .
J55 – 94# Big Omega
P110 – 72# BTC
C95 – 58.4# New Vam

46. Intermediate – 9 5/8” 5000 ft – Expected LOT = 17.5 ppg
Conductor 20” X 2 jts
Surface – 13 3/8” – 1500 ft. Expected LOT = 14.5 ppg
Production Casing 7” – 9000 ft.
4 1/2” Liner – 8500 - 10,000 ft.
P110 15.1# New Vam
ABC Productive Sands – from 9300 to 1000 ft. Estimated formation pressure = 7500 psi. H2S
content = 0 ppm. BHT = 180oF.
Exercise # Group 2
Discussion Groups
1) Design a basic wellhead and Tree for the following development well.
3 ½” Production Tubing
The formation between 5000 and 9000 ft is a highly compacted shale with sand
stringers between 7000 and 8000 ft. These stringers could contain pockets of gas.
The mud weight for this section will start at 14.0 ppg and will be increased
progressively to 15.5 ppg.
The formation between 1500 and 5000 ft is a plastic clay. The mud weight for this
section will start at 9.0 ppg and will be increased progressively to 10.5 ppg.
K55 – 68# BTC
P110 – 47 # BTC
C95 – 35# New Vam

47. • Describe the functions of a Wellhead
• Describe a casing head housing
• Describe a casing head spool
• Describe a tubing spool and hanger
• Describe the seals in a wellhead system
• Design a basic wellhead system
End of Wellhead