CHOKE VALVE WITH PRESSURE TRANSMITTERS

VOLET DE DEPART AVEC TRANSMETTEURS DE PRESSION

English Abstract

In a sub-sea wellhead insert-type choke valve having a bonnet a pair of pressure transmitters are mounted in the bonnet. One transmitter is connected by a passageway with the annular clearance between the cartridge of the insert assembly and the valve body. This transmitter measures the pressure of the fluid in the clearance and transmits signals indicative thereof to a receiver at surface. The other transmitter is connected by a passageway with the fluid in the valve outlet, measures the pressure of this fluid and transmits signals indicative thereof to the receiver. In this way the high and low pressures upstream and downstream of the choke valve flow trim are monitored by transmitters, which can be serviced by bringing the insert assembly to surface.

French Abstract

Dans un volet de départ à tête de puits sous-marine interne dotée d'un capot d'une paire de transmetteurs de pression sont montés sur le capot. Un transmetteur est connecté par un passage au jeu annulaire entre la cartouche de l'ensemble interne et le corps de soupape. Ce transmetteur mesure la pression du liquide dans le jeu et transmet des signaux indiquant ceci à un récepteur à la surface. L'autre transmetteur est connecté par un passage au liquide dans la sortie de soupape, mesure la pression de ce liquide et transmet des signaux indiquant ceci au récepteur. De cette façon les hautes et basses pressions en amont et en aval du volet de départ d'équilibrage d'écoulement sont surveillées par les transmetteurs, qui peuvent être entretenus en amenant l'ensemble interne à la surface.

Claims

7
THE EMBODIMENTS OF THE INVENTION IN WHICH AN
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:
1. A sub-sea choke valve comprising:
a valve body forming a bore extending therethrough which provides an inlet, an
outlet and an insert chamber;
a removable insert assembly positioned in the insert chamber and comprising
a tubular cartridge having a side wall forming an internal bore and having a
port
communicating with the body inlet, the cartridge having an outside surface
forming an
annular clearance with the body, whereby high pressure fluid entering through
the body
inlet penetrates into the clearance,
a bonnet connected with and closing the ends of the cartridge and the body,
the
bonnet being disengagably connected with the body,
a pressure reducing flow trim positioned in the cartridge bore, the flow trim
having a restrictive opening whereby fluid from the body inlet may enter the
flow trim
at reduced pressure and pass through the outlet,
the bonnet having an end surface,
the bonnet forming a first passageway extending from its top end surface and
communicating with the clearance,
the bonnet further forming a second passageway extending from its end surface
and communicating with the bottom outlet,
a first pressure transmitter positioned within the bonnet and connected with
the
first passageway for measuring the high pressure in the clearance and
transmitting
signals indicative thereof, and

8
a second pressure transmitter positioned within the bonnet and connected with
the second passageway for measuring the reduced pressure in the bottom and
transmitting signals indicative thereof.
2. A sub-sea choke valve comprising:
a valve body forming a T-shaped bore extending therethrough which provides a
horizontal side inlet, a vertical bottom outlet and a vertical insert chamber;
a removable insert assembly positioned in the insert chamber and comprising
a vertical tubular cartridge having a side wall forming an internal bore and
having a side port communicating with the body inlet, the cartridge having an
outside
surface forming an annular clearance with the body, whereby high pressure
fluid
entering through the body inlet penetrates into the clearance,
a bonnet connected with and closing the upper ends of the cartridge and the
body, the bonnet being disengagably connected with the body,
a pressure reducing flow trim positioned in the cartridge bore, the flow trim
comprising a tubular cage, aligned with the body outlet, and a throttling
sleeve
slideable over the cage, the cage having a side wall forming an internal bore
and
restrictive flow ports aligned with the cartridge side port and the inlet,
whereby fluid
from the body inlet may enter the cage bore at reduced pressure and pass
through the
bottom outlet,
stem means, extending through the bonnet, for biasing the throttling sleeve
over
the cage ports, the stem means and throttling sleeve combining to form a first
passageway communicating with the cage bore and the bottom outlet,
the bonnet having a top end surface,

9
the bonnet forming a first passageway extending from its top end surface and
communicating with the clearance,
the bonnet further forming a second passageway extending from its top end
surface and communicating with the bottom outlet through the cage bore,
a first pressure transmitter positioned within the bonnet and connected with
the
first passageway for measuring the high pressure in the clearance and
transmitting
signals indicative thereof, and
a second pressure transmitter positioned within the bonnet and connected with
the second passageway for measuring the reduced pressure in the bottom outlet
and
transmitting signals indicative thereof.

Description

',i
's"z CA 02369574 2002-O1-25
an
1 "CHOKE VALVE WITH PRESSURE TRANSMITTERS"
2
3
4 FIELD OF THE INVENTION
6 The present invention relates to a sub-sea choke valve having pressure
sensing
7 transmitters.
8
9 BACKGROUND OF THE INVENTION
11 A choke valve is a throttling device. It is conxmonly used as part of an
oil or
12 gas field wel~head. It functions to reduce the pressure of the fluid
flowing through the
13 valve. Choke valves are placed on the production "tree" of an oil or gas
wellhead
14 assembly to control the flow of produced fluid from a reservoir into the
production flow
line. They are used on wellheads located on land and on off-shore wellheads
located
16 beneath the surface of the ocean.
17 A choke valve incorporates what is referred to as a "flow trim". The flow
trim
18 is positioned within the choke valve at the intersection of the choke
valve's inlet and
19 outlet. The flow trim commonly comprises a stationary tubular cylinder
referred to as a
"cage". The cage is positioned transverse to the inlet and its bore is axially
aligned
21 with the outlet. The cage has restrictive flow ports extending through its
sidewall.
22 Fluid enters the cage from the choke valve inlet, passes through the ports
and changes
23 direction to leave the cage bore through the valve outlet.
{ EM185791.DOC;3 }

CA 02369574 2002-O1-25
2
1 Such a flow trim also comprises a tubular throttling sleeve that slides over
the
2 cage. The sleeve acts to reduce or increase the area of the ports. An
actuator, such as a
3 threaded stem assembly, is provided to bias the sleevE; back and forth along
the cage.
4 The amount of fluid that passes through the flow trim is dependent on the
relative
position of the sleeve on the cage and the amount of port area that is
revealed by the
6 sleeve.
7 Sub-sea oil or gas wells can be as deep as 600() feet below sea level. At
these
8 depths, maintenance on the wellhead assemblies cannot be performed manually.
An
9 unmanned, remotely operated vehicle, referred to as an "ROV", is used to
approach the
wellhead and carry out maintenance functions. To aid in servicing sub-sea
choke
11 valves, choke valves have their internal components, including the flow
trim,
12 assembled into a modular sub-assembly. The sub-assembly is referred to as
an "insert
13 assembly" and is inserted into the choke valve body and clamped into
position.
14 A typical prior art sub-sea choke valve a is shown in Figure 1. It
comprises a
choke body b forming a T-shaped bore c that provides a horizontal inlet d, a
vertical
16 bottom outlet a and an upper vertical component chamber f. A removable
insert
17 assembly g is positioned in the component chamber f, extending transversely
of the
18 inlet d. The insert assembly g comprises a tubular cartridge h, forming a
side port i, a
19 flow trim j comprising a cage k and throttling sleeve l, a collar assembly
m and a
bonnet n. The bonnet n is disengagably clamped to the body b. It closes the
upper ends
21 of the valve body b and the cartridge h. The stem assembly m extends
through the
22 bonnet n into the cartridge bore o to bias the sleeve 1 along the cage k to
throttle the
23 restrictive flow ports p.
{EM185791.DOC;3 }

CA 02369574 2002-O1-25
3
1 The choke valve 'sees' or experiences relatively high and relatively low
fluid
2 pressures. More particularly, the fluid flowing in through the valve inlet d
from the
3 well (not shown) has a high pressure. When the fluid passes through the
restrictive
4 cage ports p, it undergoes a considerable pressure drop. So the fluid
passing through
the cage bore q and the valve outlet a is at lower pressure than that in the
body inlet d.
6 The high pressure fluid penetrates into an annular clearance r between the
7 cartridge h and the internal bore surface s of the body b. Also, the low
pressure fluid in
8 the cage bore q and valve outlet a penetrates through communication ports t
in the end
9 wall of the throttling sleeve I and into a passageway a extending partway
along the
length of the collar assembly m.
11 When the flow trim,j becomes worn beyond its useful service life due to
erosion
12 and corrosion caused by particles and corrosive agents in the produced
substances, an
13 ROV is used to approach the choke valve a, unclamp the insert assembly g
from the
14 choke valve body b and attach a cable to the insert assembly g, so that it
may be raised
to the surface for replacement or repair. The ROV then installs a new insert
assembly
lb and clamps it into position. This procedure eliminates the need to raise
the whole
17 wellhead assembly to the surface to service a worn choke valve.
18 In order to efficiently produce a reservoir, it is necessary to monitor the
pressure
19 upstream and downstream of the choke valve. This is done to ensure that
damage to
the formation does not occur and to ensure that well production is maximized.
This
21 process has been, historically, accomplished through the installation of
pressure
22 transmitters into the flow lines upstream and downstream of the choke
valve. The
23 pressure read by the upstream and downstream pressure transmitters is sent
to a remote
24 location for monitoring, so that a choke valve controller can remotely bias
the flow trim
{ EM 185791.DOC;3 }

CA 02369574 2002-O1-25
4
1 to affect the desired downstream flow line pressure. The controller sends
electrical
2 signals to means, associated with the choke valve, fox adjusting the flow
trim.
3 A problem, however, exists with this process due to the unreliable nature of
4 these electronic pressure transmitters, which have a limited service life.
Replacing the
pressure transmitters after they have served their useful life has heretofore
required that
6 the whole wellhead assembly be raised to the surface. This is a time-
consuming and
7 costly operation that shuts down well production for the duration of the
repair.
8 The present invention proposes a modified choke valve that eliminates the
need
9 to raise a sub-sea wellhead assembly to the surface to replace or repair
pressure
transmitters.
11
12 SUMMARY OF THE INVENTION
13 The invention involves locating one or preferably a pair of pressure
transmitters
14 in the upper end of the bonnet of the insert assembly. One transmitter is
connected by a
first passageway extending through the bonnet to communicate with the annular
16 clearance between the cartridge and the valve body. This transmitter thus
can measure
17 the high pressure of the incoming fluid and transmit a signal indicative
thereof to a
18 remote receiver. A second transmitter is connected by a second passageway,
extending
19 through the bonnet, which communicates with the valve outlet. This
transmitter thus
can measure the pressure of the fluid that has undergone a pressure drop by
passing
21 through the flow trim. It can transmit a signal indicative of this reduced
pressure to the
22 remote receiver.
{EM185791.DOC;3 }

CA 02369574 2004-03-30
1 By positioning one or both of the transmitters in the bonnet of the
removable
2 insert assembly, they can now be replaced or repaired economically by
bringing the
3 choke insert assembly to surface.
4
5 DESCRIPTION OF THE DRAWINGS
6 Figure 1 is a cross-sectional side view of a conventional sub-sea choke
valve
7 insert installed in a choke valve body;
8 Figure 2 is a cross-sectional side view of a modified choke valve having a
9 pressure transmitter installed in the bonnet and connected with a passageway
connecting with the annular clearance between the cartridge and valve body;
11 Figure 3 is a cross-sectional side view of the choke valve of Figure 2,
showing a
12 pressure transmitter installed in the bonnet and connected with a
passageway
13 communicating with the bore of the flow trim cage; and
14 Figure 4 is an external side view of a conventional pressure transmitter.
16 DESCRIPTION OF THE PREFERRED EMBODIMENT
17 Figures 1 - 3 illustrate a choke valve 1 whose main components have been
18 described in the Background section of this specification.
19 However the choke valve 1 has been modified in the following respects:
~ a pair of counterbores 2, 3 are provided, extending into the bonnet 4 from
its
21 top end surface 5;
22 ~ the counterbores 2,3 are each internally threaded at 6;
23 ~ a pair of known pressure transmitters 7,8, such as the product supplied
by
24 Custom Components of Edmonton, Alberta under designation # SK 010629Th'',
{E4161734.DOC;1 }

CA 02369574 2002-O1-25
6
1 are positioned and screw-threaded in place in the counterbores 2,3. Each
2 pressure transmitter is operative to measure pressure and transmit signals
3 indicative thereof to a remote receiver (not shown);
4 ~ the counterbore 2 is connected by a passageway 9 with the annular
clearance
10, formed between the cartridge 11 and body bore surface 12. Thus the
6 high pressure incoming fluid entering the body inlet 13 comes into contact
7 with the transmi ter 7 through the clearance 10 and passageway 9. The
8 transmitter 7 can therefore monitor this pressure and transmit signals
9 indicative thereon;
~ the counterbore 3 is connected by a passageway 14 with a passageway 15
11 formed by communication ports 16 in the end wall 17 of the throttling
12 sleeve 18 and a passageway 19 leading through and along the stem assembly
13 20.
14 The fluid from the bore 21 of the cage 22 can therefore penetrate to the
transmitter 8. This transmitter 8 can therefore monitor the reduced pressure
of the fluid
16 in the cage bore 21 and transmit signals indicative thereof to the
receiver.
{EM185791.DOC;3}

Representative Drawing