Note: Descriptions are shown in the official language in which they were submitted.
EIJROP. PATENTAMT NR.°79 S.7
~R~ V1~ED ~
' ~ 1d~01/J'J)
APQ,'~RATUS FOR COi~JTROLL3i\(G AyD MO1V]TCR1NG
A D04ViVHOLE O1L/WATEF~ SEPARATa9
Baci<ground cf the lnvenn~on
Field of he Invention
The invention relates generally to systems for separating water from
hydrocarbons (e.g. oil) in a well and in particular to methods and apparatus
for monitoring and controlling a downhole oil/wat~r separator.
a
Prior Art
in an oil well, a quanTity of water left from "well completion'' or from
"water flooding" is mixed with the oil during production and both fluids flow
to the surface from underground formations. The water is typically separated
m at The surface and then injected back into the underground formations. As
the vvater-oil ratio (WOR) increases, the cost of operating the wel'
increases.
Much of the cost is in managing the ever increasing volumes of water that
must be lifted to the surface, separated, treated, pipelined and injected
back into the formations. As the WOR increases, the profitability of the weft
2u is diminished until it is no longer economically possible to continue
production. This often results in leaving large amounts of oil in place in the
formation.
The excessive cost of separating water from oil at the surface of a weil
has lead to downhole separation systems. U.S, Patent 5,269,153 discloses a
?5 downhole separation system which is shown in FIGURE 1. The well 13
comprises a downhole oil/water separation system including a cyclone
separator 1 1 having a separation chamber 15 wherein liquids of different
densities ere separated. Mixed liquids enter through inlet 17 at a high
tangential speed so as to generate the required centrifugal force for
~o subsequent separation and pass into separation chamber 15. A first outlet
19 is provided for liquids having a first density and a second outlet 21 is
! AMENDED S'~~~T
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provided for liquids having a second density. A stream of mainly oil flows
out or' outlet 19 and along recovery conduit 27. A steam of mainly water
passes through outlet 21 imp disposal conduit 33 and is infected into the
'ormation through injection perforations 34.
While down hole separation systems have improved well performance,
there is a need in the art for improved downhole oillwater separation
systems. In particular, there is a need for downhole oillwater separation
systems that can monitor parameters downhole and control 'he downhole
oii/water si?parator based on monitored parameters so as to achieve the
to proper separation and to optimize the performance of the separator. This is
well appreciated when the feed entering the separator varies in properties
such as oil and water viscosity which depends strongly on temperature and
more importantly the water-oil ratio.
L~ Summary of the Invention'
The above-discussed and other drawbacks and deficiencies of the prior
art are overcome or alleviated by the apparatus for monitoring and contrclling
a downhole oil/water separator of the present invention. The present
invention is a computer controlled downhole oillwater separation system. A
?0 hydrocyclone separator is positioned downhole for receiving production
fluid
and separating oil and water contained in the production fluid. Sensors are
positioned downhole for monitoring parameters and generating sensing
signals corresponding to the parameters. A microprocessor based controller
receives the sensing signals and provides controlling signals to one or ,more
25 control devices to optimize the operation of the downhole oil/water
separation system.
The computer controlled downhole oil/water separation system reduces
the amount of water pumped to the surface of the well, The system can also
detect upset conditions when the water percentage becomes too high and
~o cease production from a zone before excessive water is pumped to the
surface. By reducing the amount of water pumped to the surface, the
AMENGSG SWE
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expense of processing and injecting water back into the formation is ; educed
and well profitability is enhanced.
The aoove-discussed and other features and advantages of the present
invention will be appreciated and understood by those spilled in the art from
the following detailed description and drawings. '
Brief Description of the Drawin4s
F~eferring now to the drawings wherein like elements are numbered
alike in the several FIGURES:
!U FIGURE 1 is a diagram of a conventional downhole hydrocyclone
separator;
FIGURE 2 is a diagram of a down~hole hydrocyclone separator system
of the present invention; and
FIGURE 3 ~,s a block diagram of staged hydrocyclone separators in
1~ accordance with the present invention.
Detailed Descr lotion c~f the Invention
I FIGURE 2 is a diagram of the oil/water separation system in
accordance with the present invention.' The system includes a hydrocyclone
zo ~ep2rator 40 having three fluid flow connections thereto (42, 44, 46). On.e
tYydrocyclone separator connection is ~n inlet 42 for receiving production
fluid containing a first liquid having a first density (e.g, oil) and a second
r
Iaquid having a second density (e.g. water). The input production fluid is fed
at a high tangential speed so as to generate the required centrifugal force
for
25 subsequent separation. The hydrocyclone separator is made up of a first
section 41, a second section 43 and a third section 45. The second section
i
k 3 has an apex angle of approximately 5-7 degrees. The third section 45 is a
shallow, conical tube having an apex angle of 3-5 degrees and increases the
ime for separation.
3U ~ A second fluid flow connection is a first outlet conduit 44 for the first
iquid and a third connection is a second outlet conduit 46 for the second
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liquid. The hydrocyclone separator 40 is similar to conventional liquid/liquid
hydrocyclone separators in which the heavier liquid (e.g. vvatar) is forced to
the wall of -.~~e separator under centrifugal force and directed to the second
out'et 46. The lighter liquid le.g. oil) is displaced towards the center by
buoyancy forces and flows through first outlet conduit 44. A pump 100
constituting a fluid flow control device, is located uphole in first outlet
conduit 44 to pump the oil ~o the surface if required.
The production fluid is flows into the wells, for example through
production perforations 50 formed in the well casing. A~pump 52
l0 constituting a fluid flaw control device, has pump inlets 54 through whim
production fluid is drawn and pumped along conduit 58 zo the hydrocyclone
inlet 42. A motor 56 drives pump 52. The motor 56 may be any known
type of motor including electric, hydraulic or pneumatic or be Iecated at the
surface such as a surface driven PCP or rod pump motor (no; shown). As
1~ will be described below, the motor 56 is configured to respond to a
controlling signal to change its RPM and thus the pump rate of pump 52.
Water is passed through second outlet conduit 46 and injected back into the
formation at a different stratum different from the producing hydrocarbon
formation along a line of demarcation or barrier 63 through injection
2o perforations 60. A packer 62 isolates the production perforations 50 from
the injection perforations 60.
The downhole oil/water separation system includes a controller 70
~Nhich monitors parameters of the downhole oil/water separation system and
controls operation of the system. The controller 70 includes a
25 microprocessor and other associated components such as memory, I/0 ports,
etc. that are known in the art and which can tolerate the harsh environment
downhole (high temperature, corrosion, pressure, etc.). Sensors are
employed throughout the downhole oil/water separation system for
monitoring parameters of the system and forwarding sensing signals
representative of these parameters to the controller 70. 1'he controller 70
may be located downhole as shown in FIGURE 2 or may be placed at the
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surface in which signals are transmitted across the formation through wires,
cables, fiber optic or wireless transmission, such as telemetry, An inlet
sensor 72 is positioned at the inlet of the hydrocyclone separator 40, a firs
outlet sensor 74 is positioned in the first outlet conduit 44 and a second
outlet sensor 76 is positioned in the second outlet conduit 46. In the
embodiment shown in FIGURE 2, the sensors are Connec:ed to the controller
70 through wires 80, 81 and 82, respectively. It is understood that other
communication techniques may be employed. For example, the sensors may
also communicate with the controller 70 through telemetry thereby excluding
o the need for wires 80, 81 and 82. Sensor 94 is coupled to pump 52 and
controller 70 through wires or telemetry and monitors the intake pressure at
pump 52.
The controller 70 produces controlling signals and provides the
controlling signals to one or more control devices. The fluid flow control
a devices include the motor 56, a first control valve 90 positioned in the
first
outlet conduit 44, a second control valve 92 positioned in the second outlet
conduit 46, an inlet control valve 93 positioned in the inlet of the separator
40 and pump 100. The first control valve 90 may be eliminated and f;ow
through first conduit 44 may be controlled directly by controlling pump 100
through wire 84a. Alternatively, pump 100 and first control valve 90 may be
used in conjunction. In the embodiment shown in FfGURE 2, the controller
70 is connected to the control devices through wires 83, 84, 85, 87 and
84a, respectively. It is understood that other communication techniques
may be employed. For example, the controller 70 may also communicate
25 with the control devices through telemetry thereby eliminating the need for
the wires. The controller 70 may also communicate with the surface of the
well over wire, fiber optics 86 or through telemetry. As mentioned
previously, the motor 56 may have a variety of configurations (electric,
hydraulic, pneumatic, etc.l and is adapted to adjust the motor in response to
3O a controlling signal from controller 70. The motor 56 affects the
volumetric
flow rate and pressure along conduit 58 and the downhole separator inlet 42.
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The volumetric feed rate in turn a~feczs the tangential spend and
consequently the centrifugal gravi y developed for separation. An adjustable
inlet v2lve 93 is installed at :he in et of the hydrocyclone separator. By the
adjusting the cross sectional flow area, the feed velocity and therefore the
centrifugal force can be maintain Id constant or higher independent of the
volumetric flow rate, The valve olpening 93 can be controllec by wire 87
from the controller 70. Likewise, ~ the first control valve 90 and '.he second
control valve 92 may have a vari ty of configurations, but must be able to
incrementally open and close in response to controlling signals from the
to controller 70,
The inlet sensors 72 detect the flow rate, pressure, temperature and
water percentage of the production fluid entering the inlet conduit 42.
Based on these parameters, the c ntroller 70 generates controlling signals
i and provides the controlling sign Is to the appropriate control device or
1s control devices. For example, if he hydrocyclone separator is designed to
optimally operate at a predetermined flow rate of inlet production fluid, the
controller 70 can adjust the revoLl' tions-per-minute (RPM) of motor 56 to
establish the ideal inlet flow rate, and in combination in with the valve
setting
93 which adjusts the flow area, t a optimal centrifugal force can be
?o established. Similarly the inlet pr ssure, inlet temperature and inlet
water
percentage are used to control th system. If the water percentage at the
inlet becomes too high, it may b determined that the formation ~s no longer
producing sufficient amounts of il. In this case, the motor 56 may be
increased to effect production of incremental oil.
25 The first outlet sensors 74 detect the pressure, temperature and water
percentage az the first outlet con uit 44. Sensing signals corresponding tv
these parameters are provided to controller 70 and the controller 70
generates controlling signals and provides the controlling signals to the
appropriate control device or con rol devices. The controller 70 controls the
30 control devices so that tile water percentage at first outlet conduit 44 is
a
minimum. The second outlet sensors 76 monitor pressure, flow rate, water
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percentage, solid particle Concentration and/or other vvater quality
parameters, such as pH, at the second outlet conduit 46. The controller 70
receives sensing signals from sensors 76 and generates the necessary
controlling signals. One or .-pore of the control devices are controlled so
that
the water percentage in second outlet conduit 46 is optimized.
Specific examples of how the control devices are manipulated will now
be described. The following control processes are exemplary and are not
intended to represent al( the control processes that may be executed by the
present invention. The control processes may be used alone or in
l0 combination with other control processes.
In a first control pr ocess, the pump intake pressure is monitored by
sensor 94 and a sensing signal is provided ~o the controller 70. Eased on tf~e
pump intake pressure, the controller 70 sends controlling signals to the motor
a
56 to adjust the motor speed so that the pump intake pressure is minimized.
By minimizing the pump 52 intake pressure, the well inflovv, and thus well
production, is maximized.
Another control process is based on the oil concentration in zhe second
output conduit 46 sensed by sensors 76. If the oil concentration at sensor
76 increases, second control valve 92 should be incrementally closed and/or
zo first control valve 90 may be incrementally opened. Alternatively, the
speed
of pump 100 may be increased. All of these adjustments have the effect of
increasing the oil flow rate through first outlet conduit 44. However, in this
process the water concentration in the first liquid output conduit 44 sensed
by sensors 74 should be maintained at an acceptable low level.
z5 In yet another control process, the oil concentration at the inlet conduit
42 is monitored to establish a minimum volumetric flow rate through first
outlet conduit 44.. If the oil concentration is high at inlet conduit 42 as
monitored by sensors 72, then the first control valve 90 is opened or the
speed of pump 100 is increased to facilitate removal of the oil.
Alternatively,
30 if the oil concentration at inset 42 is low, then first control valve 90 is
incrementally closed or the speed of pump 100 is reduced to prevent water
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for exiting through first ounet conduit 44.
In yet another controi process, the separator pressure differential ratio
is monitored and adjusted dependent upon the oii concentration at inlet 42,
The separator pressure differential ratio is defined as:
;i,-let pressure at 42 - outlet pressure at 44)I(inlet pressore at 42 - outlet
pressure at 46).
The ratio iden tifies what percentage of the liquid entering the separator az
inlet 42 is distributed to the first outlet conduit 44 and the second outlet
conduit 46. For a given oil concentration at the inlet 4.2, there is an
optimal
iu separator pressure differential ratio. Accordingly, the oil concentration
az
inlet 42 is monitored by sensors 72 and the first control valve 90 and/or
pump 100 and the second control valve 92 are adjusted so that the separator
pressure difi~erential ratio is optimized for the given inlet oil
concentration.
In yet another process, when the water content in the first liquid
conduit 44 exceeds an acceptable level the cross section area of valve 93
can be reduced to generate a higher veiocity and hence a higher centrifugal
force for separation. The controller 70 also signals the pump motor 56 to
increase RPM to pump against the back pressure established by the further
restriction from the inlet valve 93 given that the volumetric feeding rate is
?0 held constant.
The separator system shown in Fig. 2 may also be provided with a
pump (not shown) driven by a suitable motor, such as electric, hydraulics or
pneumatic (not shown) positioned in the conduit 46 and controlled by
controller 70. This pump increase the pressure of the water discharged from
2s the separator 40 for reinjection into the formation. This pump may be
provided in addition to pumps 52 and 100, or in lieu of one or the other of
these pumps. The sensors 72, 74, 76 and 94 may of any suitable type such
as fiber optic, infrared, or ultrasonic.
The present invention can also be modified to provide for the removal
~o of solids from the production fluid containing solids, a first liquid (e.g.
oil) and
a second liquid (e.g. water), A flow through filter (e.g. screen) maybe used
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to strain the sold material from the first and second liquids. Alternatively,
staged hydrocyclone separators may be used as shown in FIGURE 3. A feed
conduit 200 carries production fluid containing solids, a first liquid and a
second liquid. A solid/liquid separator 202 separates the solids from the two
liquids. The solids are omput through solid outlet conduit 20~ and the mixed
liquids are output through conduit 206. A liquid/liquid separator 208
operates in accordance with the system described above with reference to
FIGURE 2 and outputs the first liquid through conduit 210 and the second
liquid through conduit 212.
Lo The present invention provides for intelligent Control of a downhole
oil/water separator by including sensors, control devices and a controller
downhole with the separator. The sensors monitor parameters of the
separation system and the controller controls portions of the system to
maximize oil/water separation. The controller can also determine when the
water percentage is so high that production from a particular zone should be
discontinued. This prevents excess water from being pumped to the surface
and reduces the costs associated with processing and injecting water from
the surface back into the formation,
While preferred embodiments have been shown and described, various
?o modifications and substitutions may be made thereto without departing from
the spirit and scope of the invention. Accordingly, it is to be understood
that
the presgnt invention has been described by way of illustration and not
limitation.
0
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