Method and apparatus for controlling subsea well template production systems

Method and apparatus for remotely controlling subsea template production systems having a plurality of satellite wells and a plurality of subsea trees on the well templates uses a significantly reduced number of electrical and hydraulic lines between a surface control unit and a riser base on the seafloor. An electrohydraulic control module on the riser base receives electrical control signals and provides hydraulic output signals to operate the riser base. Electrohydraulic control modules on the templates receive electrical control signals and provide hydraulic output signals to control operation of the trees on the templates. The satellite wells are each controlled by a single hydraulic signal line connected between the surface control unit and a matrix switching control module at the satellite well. All of the electrohydraulic modules are replaceable using surface operated running tools.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to apparatus for remote control of a plurality of 
subsea devices, and more particularly to apparatus for individual control 
of a relatively large number of subsea devices using only a few electrical 
and hydraulic source lines from a surface control unit to the seafloor. 
2. Description of the Prior Art 
The production of gas and oil from offshore wells has developed into a 
major endeavor of the petroleum industry. Wells are commonly drilled 
several hundred or even several thousand feet below the surface of the 
ocean, substantially below the depth at which divers can work efficiently. 
The wells are often located in clusters with production lines extending 
from each of the wells to a production riser base on the seafloor, then 
upward to an offshore production platform. The operation of the wells must 
be controlled from the production platform or from a surface vessel. The 
testing, production and shutting down of each of the subsea wells is 
regulated by a subsea Christmas tree which is positioned on top of the 
subsea wellhead. The Christmas tree includes a plurality of valves having 
operators which are biased to a non-active position by spring returns, and 
it has been found convenient to actuate these operators by hydraulic fluid 
which is directly controlled from the production platform. For this 
purpose, a plurality of hydraulic lines are commonly run from the surface 
platform to the wellhead to open and close these valves, and to actuate 
other devices in the well and the wellhead during installation, testing 
and operating the subsea well equipment, and also during workover 
procedures being performed on the well. 
Some of the more extensive production fields include a plurality of 
templates each having several wells thereon and a plurality of individual 
or satellite wells each having a subsea tree mounted atop the well. The 
wells may be connected to a plurality of flowlines which are coupled to a 
production platform through a riser base and a production riser. There are 
numerous valves and connectors on the trees, templates and riser base 
which must be controlled in an orderly, precise and fail-safe manner. 
Prior art control systems have used hydraulic control and pressure lines 
between the production platform and the individual valves and connectors 
with a conferral line for each valve or connector to be controlled. As 
systems become larger, the number of these control lines becomes too large 
to be handled in a multi-hose bundle and costs become unreasonable. 
Other prior art control systems include electrohydraulic operators having 
electrical control lines to the operators which control hydraulic fluid to 
open and close valves. Such prior art systems have not achieved a high 
degree of confidence or use because of the large wire connectors required 
and due to problems in sealing and providing trouble-free electrical 
connectors. 
One prior art control system which uses total hydraulic control for 
operating a large number of subsea operators using only a few lines 
between a surface control center and the seafloor has been developed. The 
system called matrix switching is disclosed in a copending patent 
application Ser. No. 101,993 filed Dec. 7, 1979, by the inventor of the 
present invention. 
SUMMARY OF THE INVENTION 
The present invention overcomes some of the disadvantages of the prior art 
systems by using a plurality of electrically operated control modules in 
subsea locations where these electrical modules can be easily replaced, 
and by using hydraulically operated modules and controls where replacement 
is difficult and where long life and trouble-free operation is required. 
The use of electrically controlled modules reduces the size and cost of 
control lines between a surface control unit and a subsea riser base, and 
provides reliable control of subsea equipment. The electrical control 
modules use electrical signals to control a plurality of valves and 
operators on the riser base and use electrical signals to control the 
operation of hydraulic valves which are hydraulically coupled to other 
valves and to operators in remote or inaccessible areas.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, FIGS. 1 and 2 disclose a subsea oil and gas 
production field having a plurality of subsea templates 10a-10dmounted on 
the sea-floor F (FIG. 1) with each of the templates connected to a pair of 
satellite wells 11a-11h. The templates are connected to a subsea riser 
base 12 by a plurality of flowline bundles 16a-16d. The riser base 12 is 
connected to a production platform 17 on the water surface by a production 
riser 18. A pair of satellite wells 22a,22b are connected directly to the 
riser base 12 by a pair of flowline bundles 23a,23b. 
The production platform 17 (FIG. 2) includes a hydraulic power unit 24, an 
electrical power unit 28 and a surface control unit 29 which provide 
electrical power, electrical control signals, hydraulic power and 
hydraulic control signals to operate the various portions of the 
production field. An electrical distribution center 30 and a riser base 
control module 34, mounted on the riser base 12, utilize multiplexed 
control signals from the surface control unit 29 to provide power and 
control signals to the templates 10a-10d and to the riser base. Electrical 
power and control signals are provided to the electrical center 30 by an 
electric cable 35 secured to the outside of the riser 18 and coupled to 
the electric center 30 by a connector 36. The upper end of the cable 35 is 
coupled to the electrical power unit 28, which provides power to operate a 
plurality of electrical devices, and to the surface control unit 29 which 
controls the application of power to selected devices on the riser base 12 
and on the templates 10a-10c. A pair of hydraulic supply lines 40a,40b 
provide hydraulic power to a large number of hydraulically operated 
devices on the templates 10a-10d, in the riser base 12, and the satellite 
wells 11a-11h, 22a,22b. A plurality of hydraulic control lines 41a-41k 
each provide control signals for a corresponding one of the satellite 
wells 11a-11h and 22a,22b. The use of multiplexed signals to the 
distribution center 30 and to the riser base control module 34 greatly 
reduce the number of hydraulic and electrical lines required between the 
production platform 17 and the riser base 12. The distribution center 30 
and a control module 34 can each be replaced if necessary by using a 
running tool (not shown) to unplug a defective unit and replace it with a 
new unit. 
The lower end of the riser 18 (FIG. 2) includes an upper connector 42 and a 
lower connector 46 connected by a flexible joint 47. The riser 18 and an 
upper portion 42a of the connector 42 can be disconnected from a lower 
portion 42b and the hydraulic lines 40a,40b, 41a-41k disconnected. An 
upper portion 36a of the electrical connector 36 is mounted on the portion 
42a of the connector and a lower portion 36b is mounted on the riser base 
12 so that the electrical cable 35 is also disconnected when the connector 
36 is separated. The connector 46 can be separated to remove the flexible 
joint 47. 
Hydraulic power to operate the satellite wells 22a,22b (FIG. 2) is coupled 
to a pair of hydraulic power lines 52a,52b from the supply lines 40a,40b 
by a check valve 48a through a pair of connectors 53a,53b. Hydraulic power 
to operate the numerous hydraulically actuated devices on the riser base 
is coupled to the riser base control module 34 by a check valve 48b and a 
hydraulic power line 54. Other control components located on the riser 
base 12 include a plurality of electrical connectors 54a-54d which connect 
the electrical lines 58a-61a to the corresponding electrical lines 58b-61b 
to couple control signals from the distribution center 30 to the templates 
10a-10d. The lines 58a-61a, 58b-61b each include a plurality of electrical 
lines but are shown as single lines to simplify the drawing. The 
electrical lines provide signals to the individual lines 61c,61d (FIG. 3) 
which provide control to an electronics portion 65 (FIG. 4) in each of a 
plurality of electrohydraulic multiplexed control modules 66a-66h (FIGS. 
1-3) which control operation of a plurality of template wells 67a-67n 
(FIG. 3) on each of the templates 10a-10d. The electronics portion 65 
operates a plurality of spool valves 71 (only two are shown in FIG. 4) and 
the spool valves provide hydraulic control for a plurality of valves 72-79 
and a subsea choke 83 in a manifold module 84a-84n and in a Chirstmas tree 
85 at each of the wells 67a-67n. 
The tree valves 76,77,79 (FIG. 4) are controlled by control module 66a 
through a plurality of control lines 89a-89c that run through a tree 
flowline connector 90 and loop through a tree cap 91 to the actuators of 
the individual tree valves. Thus, when the tree cap 91 is removed, the 
valves on the Christmas tree 85 cannot be controlled by the control module 
66a. However, a running tool or workover tool can be installed atop the 
tree and various actuators can be controlled through the tool. When the 
manifold module 84a is removed, the hydraulic supply line 40c no longer 
provides pressurized hydraulic fluid to the control module 66a and the 
valves in the Christmas tree cannot be controlled by the module 66a. The 
hydraulic supply line 40c loops through the flowline connector 90, the 
tree cap 91, the connector 90 again and through the manifold module 84a to 
the control module 66a. When the tree cap 91 is removed, or the manifold 
module 84a or the control module 66a are removed, the hydraulic supply 
line 40c is interrupted so that the tree valves cannot be inadvertently 
opened or closed. 
A workover control system for operating the various connectors and 
operators in the Christmas tree when the tree cap is removed as disclosed 
in FIG. 7 includes a running tool 95 and a control unit 29 interconnected 
by a hydraulic umbilical bundle 96. Pressurized hydraulic fluid is 
supplied to the control unit 29 by a hydraulic pump 97 powered by a motor 
98 in the hydraulic power unit 24. The pump 97 delivers fluid from a 
reservoir 104 to a plurality of spool valves 105 (only one shown in FIG. 
7) each operated by a pilot 109. A plurality of hydraulic lines 110 in the 
umbilical bundle 96 provide power to operate an actuator 111 (FIG. 4) in a 
tree cap connector 115 and to operate the various valves 73-79 in the 
Christmas tree 85. 
The electro-hydraulic control modules 66a-66h (FIGS. 1, 2) each control a 
corresponding one of a plurality of satellite manifolds 116a-116b (FIG. 3, 
only two are shown). The module 66a controls the manifold 116a, in 
addition to the manifold modules 84a-84g, and in a manner similar to the 
control exercised over manifold modules 84a-84g. The electronics portion 
65 (FIG. 5) operates a plurality of spool valves 71a (only two are shown) 
and the spool valves provide hydraulic control of a plurality of valves 
72a and a subsea choke 83a in the manifold module 116a. 
The tree valves 76,77,79 (FIGS. 5, 6) in each of the satellite wells 
11a-11h and 22a,22b are controlled by a matrix switching hydraulic control 
module 117 (FIGS. 5, 6) each having a single hydraulic control line 
41a-41k (FIG. 1) and a single hydraulic supply line 40a,40b. Details of 
the matrix switching module 117 are most clearly shown in FIG. 6. The 
control module 117 includes a rotary actuator 120 connected to a rotary 
switch having a plurality of rotatable valve sections 121-127 each having 
a pressure input Pa-Pg, an output Oa-Og, and a vent Va-Vg. Each valve 
section includes a plurality of positions "a-f" each having either the 
pressure input connected to the output or having the output connected to 
the vent. Each of the pressure inputs Pa-Pg is connected to the hydraulic 
supply line 40g which is provided with pressurized fluid from the surface 
control center 29 (FIG. 2), and each of the vents Va-Vg is connected to a 
vent 129 which is vented to the sea. An accumulator 130, which is 
connected to the hydraulic line 140, aids in providing a stabilized value 
of hydraulic pressure to the valve sections 121-127. The actuator 120 is 
operated by a pilot valve 134. The rotary actuator 120 includes a 
rotatable shaft 120a which is coupled to a plurality of rotatable shafts 
121a-127a of the valve sections 121-127. 
When a hydraulic pilot line 41a is unpressurized the pilot valve 134 is in 
the position shown in FIG. 6 wherein an upper chamber 120b of the actuator 
120 is connected to the vent 129 through the valve sections "a", whereby 
the actuator shaft 120a and the valve section 121-127 remain in a 
stationary position. When pressure is admitted to the hydraulic pilot line 
41a, the spool of the valve 134 shifts so that liquid from the hydraulic 
supply line 40g is coupled through the section "b" of the pilot valve 134 
to the upper chamber 120b, causing the actuator 120 to rotate the valve 
sections 121-127 to another distinct position. When the valves 121-127 are 
in the positions shown in FIG. 6, hydraulic pressure from the hydraulic 
supply line 40g is coupled through the "a" portion of the hydraulic valve 
122 through a hydraulic line 135b to a production wing valve 73 causing 
the wing valve to open. Hydraulic fluid coupled through "a" portion of the 
valve 123 and "a" portion of the valve 126 through hydraulic lines 
135c,135f also cause a downhole safety valve 79 and a crossover valve 74 
to open. An upper master valve 77 and a lower master valve 77a are 
connected to vent 129 through hydraulic lines 135a and the "a" portion of 
the valve 121, and an annulus master valve 76 and an annulus wing valve 
73a are connected to the vent 129 by lines 135d,135e through the "a" 
portions of valve sections 124 and 125, respectively. 
The lowermost valve 127 and a plurality of pressure relief valves 151-156 
provide a predetermined upper value of pressure on the pilot line 41a at 
the control center to indicate the position of the valve 127, therefore 
also indicating the position of the rotary actuator 120 and of the other 
valves 121-126. For example, when all the valves are in their "a" 
positions, the pressure relief valve 151 is connected through "a" portion 
of the valve 127 to the pilot line 41a and limits the maximum pressure on 
the pilot line to 1000 psi. When all valves are in their "b" position, the 
pressure valve 152 limits the pressure on the pilot line 41a to 1400 psi, 
thereby indicating that the valves and the actuator are in said "b" 
positions. Further details of the matrix switching control module 117 can 
be found in a copending patent application "Matrix Switching Control of 
Subsea Production System" by the inventor of the present invention, Ser. 
No. 101,993, filed Dec. 7, 1979. 
The present invention provides means for surface control of a plurality of 
subsea wells mounted on well templates and a plurality of satellite wells, 
using a significantly reduced number of electrical and hydraulic lines 
between a surface control unit and a riser base on the seafloor. An 
electrical cable between the riser base and the surface control unit 
provides electrical signals which control a plurality of electrohydraulic 
control modules on the well templates and on the riser. These control 
modules provide hydraulic control signals to the subsea wells and to the 
riser base. The electrohydraulic control modules are replaceable using 
surface operated running tools. A single hydraulic control line between 
each of the surface control unit and a corresponding one of the satellite 
well provides control of the operation of that well through a matrix 
switching circuit. 
Although the best mode contemplated for carrying out the present invention 
has been herein shown and described, it will be apparent that modification 
and variation may be made without departing from what is regarded to be 
the subject matter of the invention.