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					            WELLCOMPLETIONS




Wellheads         Revision 1.0   Page 1
                                                  Contents

WELLHEADS

TRAINING TARGETS: ......................................................................... 4

CASING HEAD HOUSING .................................................................. 5

CASING HEAD SPOOLS .................................................................... 6

CASING HANGERS ............................................................................ 6

TUBING HEAD SPOOLS AND HANGERS .......................................... 7

CAMERON DCB TUBING HEAD SPOOL............................................ 8

DCB HANGER ..................................................................................... 8

CONROL LINE PACK-OFF ................................................................. 9

CAMERON "SRT" TUBING HEAD SPOOL ......................................... 10

THE "SRT" HANGER NIPPLE/PACK OFF ASSEMBLY ...................... 11

SIMPLIFIED WELLHEAD ARRANGEMENT ........................................ 12

BACK PRESSURE VALVES AND PLUGS .......................................... 13

TYPE "H" TEST PLUG ........................................................................ 13

TYPE "H" BACK PRESSURE VALVE .................................................. 14

TYPE "H" TWO-WAY CHECK VALVE ................................................. 15

CHOKES ............................................................................................. 16

POSITIVE CHOKES ............................................................................ 17

BEAN CHANGE AND INSPECTION.................................................... 18




Wellheads                                             Revision 1.0                                        Page 2
ADJUSTABLE CHOKES...................................................................... 19

BAKER MODEL "D" PERMANENT PACKER ...................................... 20

"G" LOCATOR AND "E" ANCHOR SEAL ASSEMBLIES ..................... 21

THE "H" SSCSV .................................................................................. 22

OILWELL COMPLETION..................................................................... 23




Wellheads                                           Revision 1.0                                      Page 3
                               WELLHEADS



TRAINING TARGETS:

The aim of this section is to help you gain a knowledge of wellheads, chokes and
back pressure valves used in .

When you have completed this section you will be able to:
    State the purpose of wellheads.

    List the different types of wellheads.

    Identify the wellhead components.

    Name the different types of chokes.

    Name the different types of back pressure valves.




Wellheads                             Revision 1.0                        Page 4
                       WELLHEAD EQUIPMENT


CASING HEAD HOUSING

The casing head housing is the first wellhead component which is installed on a
conventional well and it serves as a connector between the surface casing and the
B.O.P. during drilling and later it serves as a connector to the other wellhead
components.


                                                     The casing head housing has a
                                                     bowl preparation to accept the
                                                     casing hanger which suspends
                                                     the intermediate casing string.
                                                     After the intermediate casing
                                                     has been run and hung off, a
                                                     casing spool is installed above
                                                     the casing head housing.


                                                     The casing spool serves the
                                                     same basic purpose as the
                                                     casing head housing in that it
                                                     acts as a connector and has a
                                                     similar bowl preparation for a
                                                     casing hanger.



The casing head housing and casing head spools which are used on our offshore
production wells in this area is the general purpose Cameron type "WF"head.
Outlets are provided on all casing head housings for access to the annulus and
these can be either threaded or flanged.




Wellheads                             Revision 1.0                            Page 5
CASING HEAD SPOOLS




Casing head spools have similar top flange and bowl configurations as described
for casing head housings. Casing head spools have a flanged or clamp hub bottom
connection.



CASING HANGERS

Casing hangers are used to suspend the casing from the casing head and seal off
the annulus. There are several types of hangers which are suitable for use with the
"WF" head and the Cameron "BRX" hanger has been selected for use in this area.


                                     The "BRX" hanger is a bollweevil or
                                     threaded suspension hanger. It has "L" type
                                     resilient seal rings on the neck and an O- ring
                                     seal on the tapered portion of the hanger
                                     body for an annulus seal.




Wellheads                              Revision 1.0                           Page 6
TUBING HEAD SPOOLS AND HANGERS

The tubing head spool and hanger are used to suspend one or more strings of
tubing. The tubing head spool is installed over the last casing spool and it allows
full opening into the casing over which it is used so that drilling tools may be run
through as necessary and to enable the production packers to be run in with the
tubing if required.

The preparation in the top of the
spool must be capable of supporting
the full weight of the tubing string
plus any test or well pressure that
may be applied above the hanger
mechanism. The tiedown screws in
the bowl preparation energize the
hanger seals or in some cases, simply
hold the hanger in place. In the case
of multiple completions the tubing
head bowl must also be designed in
such a manner that the individual
hanger segments are properly
orientated.


Tubing heads are grouped into two
main categories according to their
primary function i.e. single and
multiple completion.


For single completions the Cameron "SRT" head or the Cameron "DC-B" spool
are used, with the latter being used in all dual completions.




Wellheads                               Revision 1.0                          Page 7
CAMERON DCB TUBING HEAD SPOOL

The type "DC-B" tubing head spool was designed to receive the dual segmented
"DC-B" hanger ; however by using the "DC-FBB" tubing hanger, it can be used
for single completions.




This spool has tie down screws in the top flange to lock the tubing hanger in place
and a plastic injection port to energize the hanger body seal. This provides an
annulus seal around both tubing hangers and the tubing head spool bore. The new
type "DC-B" spool provides an exit for the control line through the top flange. A
hub is provided on the bottom to accommodate a Cameron clamp connection.


DCB HANGER


The Cameron "DC-B" hanger consists of
two segments designed for supporting and
sealing two strings of tubing side by side
for parallel completions. With both hanger
halves landed, locked down and packed
off, the "DC-B" hanger will withstand
pressure from above equivalent to the full
working pressure of the tubing head spool
top flange, acting on top of the hanger.




Wellheads                              Revision 1.0                          Page 8
CONROL LINE PACK-OFF

Each "DC-B" hanger segment is provided with a control line preparation.
On the old type hanger, the control line is taken from the bottom of the hanger to a
seal sub on top and exits through the side of a separate double studded adaptor
flange, while on the new type, the control line exits on the side of the hanger
segment, through the top flange of the tubing head spool.




Each hanger segment has a preparation for a type "H" back pressure valve.




Wellheads                              Revision 1.0                           Page 9
CAMERON "SRT" TUBING HEAD SPOOL


The type "SRT" tubing head spool is designed to receive the tubing hanger nipple
and pack off assembly. The "SRT" tubing head spool is provided with retractable
rams which support the hanger nipple.




The tubing head spool also has tie down bolts in the top flange to energise and
lock the pack off assembly and it has a preparation to exit the control line. A hub
is provided on the bottom to accommodate a Cameron clamp connection.




Wellheads                              Revision 1.0                         Page 10
THE "SRT" HANGER NIPPLE/PACK OFF ASSEMBLY

The Cameron hanger nipple is designed to support a single string of tubing
whenever it is required to land the string in tension. The seal between the hanger
nipple and the tubing head bore is provided by use of the pack off assembly.




The hanger nipple can be lowered past the point of suspension in order to space
out prior to hanging the tubing off in tension. It is provided with a control line
preparation as well as a type "H" back pressure valve preparation for 3.1/2" tubing
or an Otis type "R" 4.313" profile for 5" size.




Wellheads                              Revision 1.0                         Page 11
SIMPLIFIED WELLHEAD ARRANGEMENT




Wellheads               Revision 1.0   Page 12
BACK PRESSURE VALVES AND PLUGS

Most tubing hangers in use in this area have special threads machined in the bore
to accept type "H" back pressure valves and plugs. The insertion and removal of
these valves and plugs is done mostly with the well under pressure. The
installation and removal tools are shown below.




TYPE "H" TEST PLUG


                           The type "H" test plug is a blank plug which can be
                           made up into the standard type "H" thread in the
                           tubing hanger. It is used to plug the tubing and test the
                           tree upper section. It does not have any facility for
                           bleeding off tubing pressure before removal and
                           because of this great caution should be exercised
                           when using this plug.




Wellheads                             Revision 1.0                           Page 13
TYPE "H" BACK PRESSURE VALVE

The "H" Back Pressure Valve was designed to seal off well pressures up to
103400 kPa(15,000 psi) during removal of the blowout preventers and installation
of the Christmas tree. It can be run through a tree having the same nominal size as
the back pressure valve, i.e. a 80 mm(3") back pressure valve can be run through a
80 mm(3") master valve.




The back pressure valve body has a special 90degrees left-hand thread on the
O.D. with a compression seal ring, which is energised by engagement with the
back pressure valve threads in the hanger body.

The back pressure valve has a spring loaded, stainless steel, inner check valve
which has a moulded resilient insert seal. This check valve will confine tubing
pressure but will allow fluid to be pumped down through the tree into the tubing.
The inner check valve is mechanically held open during its removal and
installation to avoid a pressure differential across the back pressure valve.




Wellheads                              Revision 1.0                         Page 14
TYPE "H" TWO-WAY CHECK VALVE

The type "H" two-way check valve can be used to plug off tubing and test the
Xmas tree and after this exercise has been carried out then the tubing pressure, if
any, can be bled off. The valve is suitable for service up to 103400 kPa (15,000
psi) maximum and for higher pressure then the solid plug must be used.




The "two-way check" is a steel ball which seals on an upper seat to seal off tubing
pressure and a lower seat to seal off pressure from above. A special removing
screw is used to unseat the ball so that tubing pressure may be bled off if
necessary prior to the removal of the check valve.

Fluids cannot be pumped through this valve and should it be desirable to do so
prior to testing the Christmas tree then the standard "H" type back pressure valve
should be used. For testing the Christmas tree the "two-way check" should be
substituted for the standard "H" type back pressure valve.




Wellheads                              Revision 1.0                         Page 15
CHOKES

A choke is a device which has a built in restriction called an orifice which is used
to control flow. This restriction can be either adjustable or fixed and it can be
replaced in the field should it wear out. The underlying principle of a choke is that
more fluids or gases can flow through a big hole than through a small one and by
regulating the size of the hole, the flow can be controlled.

                                         On our offshore wells the chokes are
                                         mounted downstream of the surface
                                         safety valve and are used to control the
                                         flow of well fluids. The chokes are
                                         installed in such a manner that the flow
                                         of fluids is away from the bonnet or
                                         blanking plug so that any abrasive cutting
                                         action of the well fluids is minimized.
                                         In operations the master valve and the
                                         flowline valve, downstream of the choke,
                                         are used to shut the well off and isolate
                                         the choke when the choke components
need to be either checked or changed. In addition to controlling the flow of well
fluids the choke also reduces the pressure on the flowline to an acceptable level.

There are two main categories of chokes - positive and adjustable. On our multi
well platforms the Cameron "H-2" positive choke is installed on the Christmas
tree. Adjustable chokes in our production operations are used principally on the
gas lift system.




Wellheads                               Revision 1.0                          Page 16
POSITIVE CHOKES

A positive choke is one which has replaceable elements having fixed orifice
dimensions which are called flow beans, beans are precision bored orifices
varying from 1 1/2 to 6 inches in length depending on the type and are available in
sizes ranging from 1/16" up to 64/64




The actual life of the bean will depend on the service in which it is used and
should there be sand in the wellstream, then this will considerably reduce its life.

When the wellstream contains sand, it is inadvisable to use the standard bean and
for this sort of service, beans are available with tungsten carbide or ceramic
linings. Of the two types of lining available tungsten carbide is the hardest and
most wear resistant. The ceramic lining approaches the hardness of tungsten
carbide, however its wear resistance is not as good but it is considerably cheaper.




Wellheads                              Revision 1.0                          Page 17
BEAN CHANGE AND INSPECTION




The bean should be periodically inspected and the following sequence should be
adhered to when isolating the choke

    1 Close the valve downstream of the bean box.
    2 Close the valve upstream of the bean box. Do not use the surface
      safety valve for this purpose.
    3 Bleed off the pressure between the valves.
    4 Check/change bean.
    5 Open upstream valve.
    6 Open downstream valve.




Wellheads                              Revision 1.0                     Page 18
ADJUSTABLE CHOKES

An adjustable choke is one which has an externally controlled variable area orifice
with an external mechanism to indicate the orifice size. In this area the most
commonly used positive choke is the Cameron "H-2" model and this type can
quickly be converted into an adjustable choke when required. The lock nut,
blanking plug and bean are removed from the fixed choke and a valve seat, needle
assembly and lock nut do the conversion to an adjustable choke.




The adjustable choke should never be used as a valve i.e. to provide fluid tight
shut-off, this is because the needle and seat are made of some specially hardened
steel alloy and when forcing the needle against the seat this could well damage the
hard trim.




Wellheads                              Revision 1.0                         Page 19
BAKER MODEL "D" PERMANENT PACKER
      Shown below is a simplified cross section of the Baker model "D"
permanent production packer. In its set position the sealing element is compressed
between the cones (A) which are locked between the opposing slips (B)




preventing movement in either direction. Expanding metal backup ring (C)
contains the sealing element and prevents extrusion. The internal slip arrangement
(F) locks the setting force into the packer. A flapper (H), which is optional, can
prevent flow from a lower zone when the tubing is removed from the packer.
In its preset state, the cone (A) are shear-pinned to the body (D). The slips form a
complete ring, and have vertical slots cut partway through them. When they are forced
along the cones, in setting, the slips will divide into segments.

The electric setting tool is attached to an adaptor kit which is in turn attached to the upper
body of the packer by the square left hand thread (G). The principle of setting this packer
is to pull upwards on the inner body (D) and simultaneously drive downwards on the
(outer) setting sleeve (E). The actuating energy for this operation is derived from an
electrically ignited combustible power charge, the burning (not explosion) of which
develops very high pressure gas that acts on a piston and cross link sleeve which converts
the pressure energy to a mechanical force. It is this mechanical force which shears the
pins holding the cones to the body, compresses the sealing element, and sets the slips.




Wellheads                                   Revision 1.0                              Page 20
"G" LOCATOR AND "E" ANCHOR SEAL ASSEMBLIES
The anchor seal assembly has a latch sleeve, threaded to match the left-hand thread of the
packer. The lower part of the sleeve, carrying the thread, has vertical slots cut in it, and
the lower flank of the thread is chamfered. On the entry into the packer the latch sleeve
collapses inwards, and then springs out to engage the thread of the packer.
                                                           The anchor seal assembly
                                                           permits the tubing to be landed
                                                           in tension. The chamfer on the
                                                           sub of the assembly, below the
                                                           latch sleeve, ensures that it will
                                                           not pull free. Landed under
                                                           sufficient tension, the tubing
                                                           will remain straight (within the
                                                           limits of deviation of the wall)
                                                           when the well is producing.
                                                           Straight tubing contributes to
                                                           the success of the wireline
                                                           operations.
                                                           The anchor seal assembly can
                                                           be released from the packer by
                                                           pulling the weight of the tubing
                                                           and turning clockwise at the
                                                           surface since the latching
                                                           sleeve is keyed to the seal
                                                           assembly.
                                                           On the locator seal assembly
                                                           shown opposite, the top collar
                                                           seats or locates, on the bevel of
                                                           the packer body, just above the
                                                           left thread. The locator seal
                                                           does not permit landing the
                                                           tubing in tension. At the best,
                                                           the full tubing weight can be
                                                           hung off at the well head.
                                                           When the well is producing,
                                                           the temperature of the tubing
                                                           will increase and consequently
                                                           the tubing will expand
                                                           longitudinally. Now with the
                                                           locator seated on the packer,
                                                           and the top of the tubing string
fixed in the tubing head, expansion can only take place at expense of buckling.
However, by using a series of seal units below the locator head, the tubing can be pulled
back a calculated distance, and then landed, leaving the locator head this same distance
above the packer, but with a seal unit still within the packer bore. This set up allows for
tubing expansion as downhole conditions change (due to the well being opened up/ closed
in or the flow rate being changed) and as the moulded seals move through the packer
bore, this action might cause wear and tear to the seals.




Wellheads                                   Revision 1.0                              Page 21
THE "H" SSCSV
This valve is a normally closed valve, precharged with a set dome pressure. It is a
pressure operated ball type safety valve designed to automatically shut in a well when the
flowing tubing pressure at the setting depth drops below the dome pressure of the valve.
A closed valve can only be opened by equalization either by wireline methods or by
pressuring the tubing.

                                                         The tubing pressure at the depth,
                                                         when higher than the dome
                                                         pressure, enters the port in the flow
                                                         tube above the piston and exerts a
                                                         downward force on it. The resulting
                                                         downward movement compresses
                                                         the spring and overcomes the dome
                                                         pressure and moves the ball and
                                                         seat assembly downwards, against
                                                         the body weldment, to rotate the
                                                         ball into the fully open position.
                                                         When the tubing pressure at depth
                                                         falls below the dome pressure, the
                                                         spring tension plus the dome
                                                         pressure forces the piston upwards
                                                         causing the body weldment to
                                                         rotate the ball into the closed
                                                         position.

                                                         The 'H' valve is usually used on the
                                                         wells that have a leaking control
                                                         line and they can replace any
                                                         SCSSV that has been discussed in
                                                         the previous pages. They can be set
                                                         at any depth in any landing nipple
                                                         with a 'W' mandrel and be hung off
                                                         anywhere in the tubing string - the
                                                         'H' valve usually operates more
                                                         satisfactorily the deeper it is set.
                                                         Occasionally, a SCSSV cannot be
                                                         retrieved      because      of     a
                                                         broken/damaged fishing neck and
                                                         in this event the 'H' valve is hung
                                                         off above the ported nipple using
                                                         the 'W' mandrel. The 'H' valve must
                                                         always be run with an equalizing
                                                         sub.




Wellheads                                 Revision 1.0                                 Page 22
OILWELL COMPLETION




Wellheads            Revision 1.0   Page 23

				
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Lingjuan Ma Lingjuan Ma MS
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