Modular control system

A control system for controlling hydrocarbon flow from a well includes a hydrocarbon module and a separate control module. The hydrocarbon module includes one or more flow passages communicating with the flow of hydrocarbons from the well. Valves are disposed in the flow passages for opening and closing the passages to flow. Each valve includes a valve member having an open and a closed position. A biasing member is provided for biasing each valve member to the closed position. The control module is positioned adjacent the hydrocarbon module and includes an actuator member for each of the valve members. The valve member and actuator member are end to end such that the actuator member may be actuated to move the valve member to the open position. The valve members and actuator members engage along a common interface so as to allow the removal of the control module without removing the hydrocarbon module. Removal of the control module requires two movements, one to disengage the actuator members from the valve members, and a second movement to disengage the control module from the hydrocarbon module.

BACKGROUND OF THE INVENTION 
The present invention relates to control systems for wellheads on an oil or 
gas well, and more particularly, to a hydrocarbon module with valves for 
controlling the flow from the wellhead and a separate control module with 
the actuators for the valves on the hydrocarbon module. 
In oil and gas fields, controls, sensors and valve actuators are 
conventionally spread over the whole structure of, for example, a subsea 
production tree. A previously accepted disadvantage of such an arrangement 
is that if any part of this equipment should fail, the tree has to be 
pulled for the damage to be corrected and this involves extensive workover 
operations and loss of production time, with the commensurate expense. 
The present invention overcomes the deficiencies of the prior art. 
SUMMARY OF THE INVENTION 
According to the present invention, an assembly of equipment for use in a 
gas or oil field comprises a hydrocarbon module containing fluid flow 
passages which are controlled by valves having moving valve parts, and a 
separate control module which contains valve actuators, and which is 
arranged to be brought into juxtaposition with and fixed with respect to 
the hydrocarbon module whereby the moving parts of the valve actuators are 
engageable with the moving valve parts across an interface between the 
modules to enable operation of the valves by the actuators. 
The control module may be fixed to the hydrocarbon module, or both modules 
may be fixed to a common base. 
The hydrocarbon module can take many forms such as a production tree, a 
manifold, a separator or a pumping head. The valves in the hydrocarbon 
module may be flow valves, chokes or connectors but without their 
actuators, the actuators being provided separately in the control module. 
Most simply the moving actuator parts are rods which, at the interface 
between the modules, are arranged to abut end to end with respective rods 
forming the moving valve parts. Preferably the valves are fail safe closed 
and the valve rods are pushed by extension of the actuator rods to open 
the respective valves. 
The actuators may be hydraulically or pneumatically operated pistons, or 
electrical actuators. A control module designed to be operated by one mode 
can be changed to one operated by different mode, e.g. an electric module 
could be replaced by an hydraulic module, without any modification to the 
hydrocarbon module. 
In case one of the actuators should become stuck in a position in which it 
extends across the interface, it is desirable that the control module is 
coupled to the hydrocarbon module in such a way that to disengage the 
control module from the hydrocarbon module, the control module undergoes a 
first movement to disengage the actuators from the moving valve parts to 
allow the valves to close, while the control module and hydrocarbon module 
are still engaged, and a second movement to disengage the control module 
from the hydrocarbon module. This ensures that the control module can be 
safely removed after the valves have closed, even if the actuators are 
stuck. 
In addition to containing the valve actuators, the control module may 
incorporate valve actuation monitoring equipment and data gathering 
systems. In this case the control module may be connected via a hub to a 
part of the hydrocarbon module which has connections downhole or by 
umbilical to other stations. 
The advantages which stem from the invention are numerous. The central 
activation of all the valves in a tree structure or other hydrocarbon 
module by actuators in the separate control module, obviously avoids the 
need to locate such actuators in the tree so that if, for example, an 
actuator should stick, it is only necessary to release and retrieve the 
control module, without plugging the well and pulling the tree. A central 
location of controls, transmitters and actuators in the control module 
eliminates the need for pipe work in the tree or other hydrocarbon module 
and eliminates the need for many hydraulic couplings and electrical 
connectors.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As illustrated in FIG. 1, the subsea wellhead 1 at the mud line 3 comprises 
the usual wellhead housing 4 containing concentric casings and a tree 6 
within a framework 7. The tree 6 is coupled to the top of the wellhead 
housing 4 by a connector 5. The tree 6 may be of the kind known as a 
"spool tree", in which the production tubing hanger has a lateral port in 
alignment with a flow port in the tree, the arrangement being such that 
after the completion strings have been pulled, through a blowout 
preventer, full bore access is provided to the well through the spool tree 
6 without the need to remove the spool tree 6. 
In the context of the present invention, the spool tree 6 provides a 
hydrocarbon module through which the flow of fluids into and out of the 
well is controlled. 
In FIG. 2 the spool tree 6 forming the hydrocarbon module is shown to 
contain several parallel valves 8, which may include an annular cross over 
valve, an annular master valve, a production master valve, a service wing 
valve, and a production wing valve and chokes 9. These are all provided 
with mutually parallel operating rods 10 which are shown in FIG. 2 
provided with extension rods 10' all terminating along a plane adjacent to 
the edge of the framework 7. Each of the valves 8 is operated against 
spring action by depression of the respective operating rod 10. 
As shown in FIG. 1, a control actuation module 11 is coupled to one side of 
the tree 6. As shown in FIG. 3, the control actuation module 11 is 
provided with four T-pieces 11', which, in plan, have a T-shape cross 
section. As shown in FIG. 2, these are arranged to slide vertically into 
V-boxes 6' on the side of the tree 6 which are provided with 
correspondingly shaped slots. In use, the control actuation module 11 is 
lowered on a suspension connection 12 and brought, with an aid of a remote 
operated vehicle, into proximity with the spool tree 6. The control 
actuation module 11 is guided by the framework 7 until the T-pieces 11' 
slot into the V-boxes 6'. The control actuation module 11 is further 
lowered onto a base 13 of the tree 6 so that it is clamped into position 
on the side of the tree 6. The control actuation module 11 also interfaces 
with valve actuation monitoring equipment and data gathering systems via a 
hub 14 shown in FIG. 3 or a connector which is provided with electrical 
and hydraulic quick connect mechanisms. 
As shown particularly in FIGS. 3A and 3B, the control actuation module 11 
incorporates actuators 15, each having a projecting actuating rod 16 
ending in a mushroom head 16'. Each rod, when the modules are 
interconnected, is aligned end to end with a respective one of the valve 
actuating rods 10. The actuators may be electrical actuators provided with 
an electric motor and gear drive, similar to that shown in U.S. Pat. No. 
4,920,811, or hydraulic actuators provided with a double acting cylinder 
arrangement. Any one of the valves 8 can then be opened by operation of 
the respective actuator 15 in the control module 11, causing the 
respective rod 16 to be extended and hence the respective rod 10 to be 
retracted. 
The principle of the invention is best illustrated by a comparison of the 
conventional arrangement as shown in FIG. 4 with the inventive arrangement 
shown in FIG. 5. In FIG. 4 the actuators 15A are provided within the tree 
26. A separate control module 17 which has numerous hydraulic and 
electrical lines is provided for the control of the valves in tree 26. A 
separate umbilical connection 18 is provided for the source of energy such 
as hydraulic and/or electrical power. By contrast, in FIG. 5, the 
actuators 15 and associated controls are provided in the separate control 
module 11 with the actuating rods 16 engaging with the respective valve 
operating rods 10 across the common interface 14 between the control 
module 11 and hydrocarbon module 6. An umbilical connection 19 for the 
source of hydraulic and/or electrical power is provided directly to the 
control module 11. 
The valve actuators 15 can operate vertically instead of horizontally and 
the control module 11 can be landed in a different attitude relative to 
the hydrocarbon module 6, subject to an appropriate interface between the 
valve moving parts, such as the rods 10, and the actuator moving parts, 
such as the rods 15. 
A valve 27 suitable for use in the hydrocarbon module 6 is shown in FIG. 6. 
The closure element is provided by a gate 20 which is shown in an open 
position in FIG. 6B and in a closed position in FIG. 6A. The gate 20 is 
connected to a stem 21 which extends out through the opposite end of the 
housing 28 of valve 27 to the gate 20 where it terminates in a mushroom 
head 22 which, in use, is engaged by an actuating rod 16. The stem 21 can 
be provided with any extension rod, for example as shown in FIG. 2 so that 
it extends to the edge of the tree 6. A spring 23 is provided in a spring 
cartridge 24 and is arranged to bias the valve 27 into a closed position 
as shown in FIG. 6A. The spring 23 is surrounded by a sleeve 25 which is 
telescopic so that it does not project beyond the mushroom head 22 when 
the valve 27 is open. Thus, when the actuating rod 16 is retracted, the 
spring 23 provides a fail safe closed operation. 
In the event of malfunction, the least reliable parts are in the control 
module 11, and module 11 can be readily disconnected and raised to the 
surface for repair without disturbing the tree 6, or having to break any 
hydrocarbon connection on the wellhead. 
If an actuating rod 16 should become stuck in a position in which it 
extends across the interface 14 between the hydrocarbon module 6 and 
control module 11, the control module 11 has to be moved first vertically 
so that the stuck actuator rod 16 is no longer in alignment with the 
respective operating rod 10, while the module 11 still remains fixed 
against horizontal movement away from the tree 6 by virtue of the 
engagement between T-pieces 11' and V-boxes 6'. This vertical movement 
releases the actuating rod 10 and allows the spring 23 to force the valve 
into a closed position. The actuating rod 16 is now isolated from the tree 
6, and the control module 11 can be removed safely by further vertical 
movement to bring the T-pieces 11' out of the V-boxes 6'. 
While a preferred embodiment of the invention has been shown and described, 
modifications thereof can be made by one skilled in the art without 
departing from the spirit of the invention.