Note: Descriptions are shown in the official language in which they were submitted.
CA 02686310 2009-11-25
MONITORING PUMP EFFICIENCY
FIELD OF THE INVENTION
100011 The present invention relates to oil wells and more particularly to
methods and systems of
controlling pumps used in the recovery of fluid therefrom.
DESCRIPTION OF THE RELATED ART
100021 In the production of crude oil from an oil bearing subterranean
reservoirs, it is often
necessary to utilize a pump to move oil from the reservoir to the surface.
This can be necessary where a
lack of pressure exists in the reservoir to "push" oil from the reservoir to
the surface or where the viscosity
of the oil is such that no amount of native pressure within the reservoir will
be sufficient to accomplish this
task. In the prior art there are numerous examples of the use of pumps of
varying kinds and configurations
to draw oil from an oil bearing subterranean reservoir to the surface through
a well bore. In utilizing a
pump in the production of crude oil from a well, a conventional approach is to
maximize the amount of
production from the well over the economic life of the well and to maximize
the volume of oil being
produced from the well over any measured period of time (also known as
"production flow rate").
Achieving these two objectives is a matter of controlling the rate and/or
frequency at which the pump pulls
fluid from the reservoir. A significant problem with the use of pumps for this
purpose is the potential for
the pump to operate at a rate faster than the reservoir can provide fluid to
the well bore. This is known as
-'pump off'. Achieving the objectives of maximizing production of a well over
its economic life, and
maximizing the production flow rate while avoiding pump off requires the
careful control of the pump to
optimize pump operation. Generally, the principle is to adjust the operation
of a pump to reflect changes in
the well, caused by changes in the flow of fluid from the oil bearing
subterranean reservoir into the well
bore. Of course, adjustments can't occur without an ability to detect those
changes in the recovery rate.
Common detection techniques include sensing torque at the pump, sensing flow
rates in a production line,
measuring a level of fluid level change in a storage tank and sensing a level
of fluid in a well bore. All of
these are aimed at detecting a change in flow of fluid from the oil bearing
subterranean reservoir into the
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well bore. The operation of the pump is then adjusted, either by way of its
"duty cycle" or by its speed, so
that when the recovery rate decreases, so does the duty cycle or speed of the
pump and vice versa.
100031 While these developments can be beneficial to producing oil from a
well, there remain
several shortcomings of conventional approaches, particularly related to the
recovery of oil from an oil-
bearing reservoir containing or carrying sediment or solid material. A
significant number of the oil
producing reservoirs of North Eastern Alberta Canada are composed of packed,
compressed but otherwise
loose or unconsolidated sands. The crude oil in these reservoirs is
particularly viscous and will not flow to
the surface through a well bore without the aid of a pump. The viscous nature
of this crude oil also makes
it ideal for moving the unconsolidated sands along with the crude oil as it is
produced from the reservoir,
thus producing sand along with the oil. The common approach to pumping this
viscous crude oil from its
native reservoir is to use a progressive cavity pump.
100041 A progressive cavity pump may also be also known as a progressing
cavity pump,
eccentric screw pump and cavity pump. This type of pump transfers fluid by
means of the progress,
through the pump, of a sequence of small, fixed shape, discrete cavities, as
its rotor is turned. The rotor is
shaped much like a corkscrew and set in a housing lined with an elastomer
shaped into cavities which are a
mirror image for the rotor and forms the stator. Rotating the rotor leads to
the volumetric flow rate being
proportional to the rotation rate (bidirectionally) and to low levels of
shearing being applied to the pumped
fluid. Hence these pumps have application for pumping of viscous materials.
The cavities of the stator taper
down toward their ends and overlap with their neighbors, so that, in general,
no flow pulsing is caused by
the arrival of cavities at the outlet, other than that caused by compression
of the fluid or pump components.
100051 Although a progressive cavity pump will tolerate fluid containing or
carrying solids, the
sands contained and carried in the viscous crude oil produced from the above
described reservoirs are
extremely abrasive and cause wear on the pump, in particular on the stator,
thus reducing the operating life
and efficiency of the pump. As shown in the prior art, this abrasion or wear
is greatly accelerated when the
rotor of the pump is rotated at higher speeds. Unless pump speed is adjusted
to account for the production
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of sand with the oil, the resulting premature or accelerated wear of the pump
may result in more frequent
downtime and repairs, thus increasing the cost of producing crude oil from the
well which the pump serves.
100061 It is also a characteristic of this type of reservoir for the
proportion of sand produced with
the oil to vary significantly and somewhat unpredictably during the pumping of
fluid from the reservoir
through a well bore. At times, high concentrations of sand can be pulled along
with the crude oil, resulting
in the pump over torquing resulting in damage to the pump and potentially
seizing up the pump. Should
this occur, the pump must be pulled from the well bore, both the pump and well
bore cleaned of
accumulated sand, the pump repaired or replaced and then the repaired or
replaced pump returned to the
well bore.
100071 Conventional approaches teach the maximizing of production flow rate
while avoiding
pump off. They do not take into consideration wear and tear on the pump or
frequency of pump
breakdown which leads to increased production costs, Nor do they address the
pumping of fluid containing
or carrying abrasive solids which may vary unpredictably in concentration
causing pump damage or
seizing, resulting in increased production costs and possible reservoir
damage. Due to the abrasive nature
of the sand produced with crude oil from a reservoir comprised of an
unconsolidated sand, a system or
apparatus designed to maximize production volume over time, while avoiding
pump off, may not respond
to the presence of, or changes in, the concentration of'such abrasives in
sufficient time to prevent damage
or degradation to the pump.
100081 Finally, the teachings of the prior art do not address maximizing of
the aggregate
amount of oil produced from of an oil well producing from an unconsolidated
sand reservoir, over the
economic life of well- The production of sand with the crude oil from this
type of reservoir is essential to
the overall productivity of the well as the removal of sand from the reservoir
forms a network of channels,
commonly known as "wormholes" from the well bore tracking off into the
reservoir. These wormholes are
essential to the successful production of oil from the reservoir as they form
from and facilitate the
production of sand from the reservoir thereby providing channels in the
reservoir allowing oil contained in
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the reservoir to flow or be drawn into the well bore thus allowing the well
bore to gain access to a large
area and volume of the reservoir and the oil contained therein. The network is
initiated during the initial
production of the well (as evidenced by initial higher volumes of sand
production), but the network
continues and must continue to grow throughout the life of the well if the
well is to remain productive. The
effect of the wormhole network is to both allow oil contained in the reservoir
to flow to the well bore and
extend the reach of the well bore into the formation containing the heavy oil
as each wormhole acts like a
conduit allowing fluid to flow to the well bore. However these wormholes cease
to grow if the pump
contained within the well bore ceases to operate for any extensive period of
time. They may also collapse
or plug with sand. If the pump contained within the well bore ceases to
operate for an extensive period of
time it is very difficult re-establish the growth of the wormhole network and
replace or re-open plugged or
collapsed wormholes. Re-starting a well bore pump that has not been operating
for an extensive period of
time usually results in the production of further significant volumes of sand
without necessarily a
corresponding increase or re-establishment of oil production at the level
enjoyed prior to the pump ceasing
to operate. As a result, the overall productivity of a well in terms of the
volume of oil that can be produced
from the well over its economic lifetime can be negatively impaired.
100091 What is required is a means not presently taught in the art which would
facilitate the
control and operation of a progressive cavity pump serving a well producing
oil from an unconsolidated
sand reservoir in order to:
= reduce, if not minimize, the frequency of repairs and downtime for the pump;
and
= increase, if not maximize, the aggregate amount of oil produced from the
well that the pump
serves over the economic life of the well.
SUMMARY OF THE GENERAL INVENTIVE CONCEPT
100101 In a first exemplary embodiment, there is provided a system for
controlling a pump used
in the recovery of oil bearing fluid materials from such a well. The system
comprises a progressive cavity
pump, a storage tank arranged to receive fluid materials from the pump and a
drive unit connected to the
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pump for delivering a drive torque to drive the pump at a corresponding pump
speed. The drive unit is
operable to vary the pump speed by one or more preset pump speed increment
values. A controller is
provided for controlling the drive unit, and a tank level sensor is in
communication with the controller. The
tank level sensor is provided for sensing the level of fluid in the storage
tank. The tank level sensor is
arranged to dispatch a tank level signal representative of the fluid level in
the tank. A speed sensor is
provided for sensing the pump speed, in one example in revolutions per minute.
The speed sensor is also in
communication with the controller for dispatching a speed signal
representative of the pump speed. Also
provided is a torque sensor for sensing the drive torque. The torque sensor is
also in communication with
the controller for dispatching a torque signal representative of the drive
torque. The controller is
configured to calculate and monitor a pump efficiency value for changes in
pump efficiency and to vary the
pump speed according to the pump efficiency value. To this end, the controller
is configured to receive
into memory:
- a preset minimum pump efficiency value;
- a preset pump speed increment value;
- a preset sampling time interval for collecting data from the tank level and
speed sensors;
- a preset maximum torque setting;
- a preset minimum pump speed;
- a preset torque override bypass slowdown time interval
- a preset maximum pump speed; and
- a preset manufacturer's pump rating value for the pump.
100111 In the first exemplary embodiment, these presets are entered into the
controller, directly
or indirectly, by a human operator or through an interface with a computer
system. The preset
manufacturer's pump rating value is an ideal volume of fluid that the pump
should produce at a prescribed
ideal operating speed over a given period of time. In one example, the preset
minimum pump efficiency
value is a fraction of the manufacturer's pump rating value, selected based on
experience with the
production history of the oil bearing subterranean reservoir. This value is
presumed to be a minimum
economic efficiency for producing fluid from the oil bearing subterranean
reservoir from the wellbore in
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question. The preset maximum and minimum pump speeds are selected based on
experience with the
production history of the oil bearing subterranean reservoir. In one example,
the maximum speed is
presumed to be the highest speed at which the pump can operate, without
encountering pump off. In one
example, the minimum speed is presumed to be the lowest speed at which the
pump can operate, while still
producing fluid from the reservoir, even where such fluid production includes
high volumes of sand,
though there may be instances in which the pump may operate below the minimum
speed. The preset
maximum torque setting is the maximum amount of torque that the drive unit can
impose on the pump
before damage to or seizing of the pump may occur.
100121 In the first exemplary embodiment, the preset pump speed increment
value is a speed
change (in one example measured in revolutions per minute (RPM)), selected
based on experience with the
production history of the oil bearing subterranean reservoir. The preset speed
increment is used for both
positive and negative changes in pump speed in most circumstances. The preset
sampling time interval is
selected based on experience with the production history of the oil bearing
subterranean reservoir, in one
example, as a balance between the expected minimum time required for obtaining
an effective
determination of changes in pump operating efficiency and the maximum time
that the pump can be
allowed to operate free of intervention without incurring significant risk of
damage to the pump. The preset
torque override bypass slowdown time interval is selected based on experience
with the type of pump and
drive unit being used and is usually a duration of time shorter than the
preset sampling time interval. An
over torque condition is usually caused by a sudden increase in the amount of
sand being drawn from the
reservoir with the oil bearing fluid. Each step change in pump speed is
employed to address the over
torque condition. A short period of time may thus be required to allow the
pump the opportunity to clear
this sudden increase in the amount (or "slug") of sand before varying the
speed if the over torque
condition does not resolve itself.
100131 In the first exemplary embodiment, the controller is further
configured, after a first
operational time period:
a) to receive the tank level signal and to determine therewith a first tank
level;
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b) and, with the first tank level, to determine a first change in tank level
over the first preset
sampling time interval;
c) and, with the first change in tank level, to calculate a first volume of
fluid collected over
the first preset sampling time interval;
d) to receive the speed signal to determine therewith a first pump speed,
e) and, with the first pump speed, the first volume, and the preset
manufacturer's pump
rating value for the pump, to calculate a first pump efficiency value;
1) to compare the first pump efficiency value with the preset minimum pump
efficiency
value:
g) arid, if the first pump efficiency value is equal to or greater than the
preset minimum
pump efficiency value, to increase the pump speed by the preset pump speed
increment value;
h) and if the first pump efficiency value is less than the preset minimum pump
efficiency
value, to decrease the pump speed by the preset pump speed increment value;
i) and to repeat steps a) through h) at the end of each sampling time interval
thereafter.
100141 In the first exemplary embodiment, the controller is further configured
to override other
functions of the control system if the torque sensor registers a torque
exceeding the preset maximum torque
setting, and to decrease the speed of the pump by the preset pump speed
increment value initially to
decrease the speed of the pump by the preset pump speed increment value and
then, at the end of each
preset torque override bypass slowdown time interval, until:
- the torque sensor registers a torque less than the preset maximum torque
setting, and
thereby to return pump control system to full normal operation; or
- the pump speed is reduced to zero.
100151 In some exemplary embodiments, the preset minimum pump efficiency value
is
calculated as the measured pump efficiency, expressed as a percentage preset
manufacturer's pump rating
value for the pump. In one example, the controller is configured to add an
operational variance factor to
the preset minimum pump efficiency value. The operational variance factor is
applied to gross up the
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minimum pump efficiency value and is used where the controller is configured
to reduce pump speed by
the preset pump speed increment value at the end of any preset sampling time
interval where the measured
pump efficiency value is greater than the preset minimum pump efficiency value
but less than the preset
minimum pump efficiency value plus the operational variance factor. In this
configuration the controller
reduces the pump speed to the preset minimum pump speed if, for two
consecutive preset sampling time
intervals, the measured pump efficiency value is less than the preset minimum
pump efficiency value.
100161 In another exemplary embodiment, there is provided a system for the
recovery of oil
bearing fluid materials from an oil well, comprising
(i) a progressive cavity pump;
(ii) a storage tank arranged to receive fluid materials from the pump;
(iii) a drive unit connected to the pump for delivering a drive torque to
drive the pump at a
corresponding pump speed, with the drive unit operable to vary the pump speed;
(iv) a controller;
(v) a tank level sensor in communication with the controller, for sensing the
level of fluid in the
storage tank, with the tank level sensor configured for dispatching a tank
level signal
representative of the tank level;
(vi) a speed sensor in communication with the controller for sensing the pump
speed, with the
speed sensor configured for dispatching a speed signal representative of the
pump speed;
(vii) a torque sensor in communication with the controller for sensing the
drive torque, with the
torque sensor configured for dispatching a torque signal representative of the
drive torque;
and
(viii) the controller configured for receiving the tank level signal, the
speed signal and the torque
signal, respectively, from the tank level sensor, the speed sensor and the
torque sensor, and
for controlling the drive unit to vary the speed of the pump by one or more
preset pump speed
increment values, the controller configured to calculate a pump efficiency
value and to
monitor torque for changes in pump efficiency and torque, and to vary the pump
speed
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according to the pump efficiency value and torque, the controller configured
to receive into
memory:
- a preset manufacturer's pump rating value for the pump;
- a preset minimum pump efficiency value;
- a preset pump speed increment value;
- a preset sampling time interval for collecting data from the tank level and
speed sensors;
- a preset maximum torque setting;
- a preset torque override bypass slowdown time interval:
- a preset minimum pump speed; and
- a preset maximum pump speed; and
at the end of a first preset sampling time interval, the controller further
configured:
a) to receive the tank level signal and to determine therewith a first tank
level;
b) with the first tank level, to determine a first change in tank level over
the first sampling
time interval;
c) and, if the tank level change is positive, to calculate a first volume of
fluid collected over
the first sampling time interval;
d) to receive the speed signal to determine therewith a first pump speed;
e) and, with the first pump speed, the first volume, and the preset
manufacturer's pump
rating value for the pump, to calculate a first pump efficiency value;
f) to compare the first pump efficiency value with the preset minimum pump
efficiency
value;
g) and if the first pump efficiency value is equal to or greater than the
preset minimum
pump efficiency value, to increase the pump speed by the preset pump speed
increment value;
h) and if the first pump efficiency value is less than the preset minimum pump
efficiency
value, to decrease the pump speed by the preset pump speed increment value;
i) and to repeat steps a) through h) at the end of each sampling time interval
thereafter;
j) to receive the torque signal from the torque sensor;
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k) and if the torque signal exceeds the preset maximum torque setting, to
override steps g)
and h) and to decrease the speed of the pump by the preset pump speed
increment value
and,
I) to repeat steps j) and k) at the end of each preset torque override bypass
slowdown time
interval until:
i) the torque sensor registers a torque less than the preset maximum torque
setting ,
thereby returning to step a); or
ii) the pump speed is reduced to zero.
100171 In some exemplary embodiments, the pump efficiency value is calculated
as the
measured pump efficiency expressed as a percentage of a rated pump efficiency.
100181 In some exemplary embodiments, the controller is configured to add an
operational
variance factor to the preset minimum pump efficiency value, the controller
further configured to reduce
the pump speed by the preset pump speed increment value where, at the end of
any preset sampling time
interval, the calculated pump efficiency value is less than the preset minimum
pump efficiency value plus
the operational variance factor, but greater than the preset minimum pump
efficiency value, and the
controller further configured to reduce the pump speed to the preset minimum
pump speed where, at the
end of each of at least two consecutive preset sampling time intervals, the
calculated pump efficiency value
is less than the preset minimum pump efficiency value.
100191 In some exemplary embodiments, the controller is configured to add an
operational
variance factor to the preset minimum pump efficiency value, the controller
further configured to make no
change to the pump speed where at the end of any preset sampling time interval
the calculated pump
efficiency value is less than the preset minimum pump efficiency value plus
the operational variance
factor, but greater than the preset minimum pump efficiency value, and the
controller further configured to
reduce the pump speed to the preset minimum pump speed where, at the end of
each of two consecutive
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preset sampling time intervals, the calculated pump efficiency value is less
than the preset minimum pump
efficiency value.
100201 In some exemplary embodiments, the drive unit includes a drive train
for driving the
pump, the drive train including a drive motor. The drive motor may include an
internal combustion engine,
an electrical drive motor, and/or an hydraulic drive motor.
100211 In some exemplary embodiments, the first pump efficiency value is
calculated according
to the formula: PIE= [(Vt / St)/(Vr/Sr)] 100, where:
- Vt is a volume of fluid collected in the tank in a predetermined sampling
time
interval, adjusted to a 24 hour period;
- St is a pump speed during the predetermined sampling time interval,
expressed in
RPM;
- Sr is a manufacturer's rated pump speed, expressed in RPM; and
- Vr is a rating for volume produced in a rated time interval adjusted to a 24
hour
period.
100221 In some exemplary embodiments, the predetermined sampling time interval
is one hour,
though other time intervals may be employed, as desired.
100231 In some exemplary embodiments, the preset torque override bypass
slowdown time
interval is a fraction of the preset sampling time interval. In one example,
the fraction is one quarter to one
half,
100241 In some exemplary embodiments, the preset speed increment value is 5
RPM, though
other speed increments may also be used as desired.
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100251 In some exemplary embodiments, the pump is driven by hydraulic fluid in
a supply line
from an external hydraulic pump and the preset maximum torque setting ranges
from about 2500 psi to
2900 psi, which reflects the pressure exerted in the hydraulic fluid used to
drive the pump.
100261 In some exemplary embodiments, the pump is driven by an electric motor
and the preset
maximum torque setting ranges from about 35 amps to about 45 amps, which
reflects the amperage draw of
the electric motor used to drive the pump.
100271 In some exemplary embodiments, the preset pump efficiency value ranges
from 25
percent to 80 percent.
100281 In some exemplary embodiments, the preset maximum pump speed is set
according to a
rated maximum pump speed.
100291 In some exemplary embodiments, the present minimum pump speed is set to
maintain a
minimum recovery flow of fluid from the well.
100301 In some exemplary embodiments, the controller is configured so that the
controller does
not increase pump speed beyond the preset maximum pump speed and does not
reduce the pump speed
below the preset minimum pump speed.
10031 In another exemplary embodiment, there is provided an oil field control
installation,
comprising a plurality of oil wells, each being independently controlled by
the system as defined above.
100321 In another exemplary embodiment, there is provided a computer-
implemented method of
controlling an oil well, comprising:
a. providing a progressive cavity pump in a well bore of the oil well;
b. providing a storage tank to receive fluid materials from the pump;
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c. providing a pump drive section connected to the pump for delivering a drive
torque to drive
the pump at a corresponding pump speed;
d. configuring the pump drive section to receive instructions to increase
speed by one or more
preset pump speed increment values;
C. providing a tank level sensor for sensing the level of fluid in the storage
tank and a speed
sensor for sensing the pump speed:
f. receiving signals from the tank level sensor and the speed sensor
indicative of tank level and
pump speed respectively;
g. providing a torque sensor for sensing a drive torque value delivered by the
pump drive section
to the pump;
h. receiving signals from the torque sensor indicative of drive torque the
torque;
i. monitoring a pump efficiency value for changes in pump efficiency and to
vary the pump
speed according to the pump efficiency value, including:
1. receiving into memory:
a. a preset minimum pump efficiency value;
b. a preset pump speed increment value;
c. a preset sampling; time interval for collecting data from the tank level
and speed sensors;
d. a preset maximum torque setting;
e. a preset torque override bypass slowdown time interval;
f. a preset minimum pump speed;
g. a preset maximum pump speed; and
h. a preset manufacturer's pump rating value for the pump;
II. and, after a first preset sampling time interval:
a. receiving the tank. level signal and determining therewith a first tank
level;
b. with the first tank level, determining a first change in tank level over
the first preset sampling time interval;
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c. with the first change in tank level, calculating a first volume of fluid
collected over the first preset sampling time interval;
d. receiving the speed signal to determine therewith a first pump speed;
e. with the first pump speed, the first volume, and the preset
manufacturer's pump rating value for the pump, calculating a first
pump efficiency value;
f. comparing the first pump efficiency value with the preset minimum
pump efficiency value;
g. and if the first pump efficiency value is equal to or greater than the
preset minimum pump efficiency value , increasing the pump speed
by the preset pump speed increment value;
h. and if the first pump efficiency value is less than the preset minimum
pump efficiency value, decreasing the pump speed toward the preset
minimum pump speed; and
i. and to repeat steps a. through h. at the end of each sampling time
interval thereafter;
j. and if, during steps a. to h., the torque sensor registers a torque
exceeding the preset maximum torque setting, overriding other
functions of the control system and decreasing the speed of the pump
by the preset pump speed increment value initially and then at the end
of each preset torque override bypass slowdown time interval. until:
- the torque sensor registers a torque less than the preset
maximum torque setting and then to return the pump control
system to full normal operation; or
- the pump speed is reduced to zero.
100331 In yet another exemplary embodiment, there is provided a computer-
implemented method
of controlling an oil well, comprising:
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a. providing a progressive cavity pump in a well bore of the oil well,
b. providing a storage tank to receive fluid materials from the pump;
c. providing a pump drive section connected to the pump for delivering a drive
torque to
drive the pump at a corresponding pump speed;
d. configuring the pump drive section to receive instructions to vary the pump
speed by one
or more preset pump speed increment values;
e. receiving signals from a tank level sensor and a speed sensor indicative of
tank level and
pump speed respectively;
f. receiving signals from a torque sensor indicative of the drive torque;
g. monitoring a pump efficiency value for changes in pump efficiency and to
vary the pump
speed according to the pump efficiency value, including:
1. receiving into memory:
a. a preset manufacturer's pump rating value for the pump;
b. a preset minimum pump efficiency value;
c. a preset pump speed increment value;
d. a preset sampling time interval for collecting data from the tank level
and speed sensors;
e. a preset maximum torque setting:
f. a preset torque override bypass slowdown time interval:
g. a preset minimum pump speed; and
h. a preset maximum pump speed; and
11. after a first preset sampling time interval:
a. receiving the tank level signal and determining therewith a first tank
level:
b. with the first tank level, determining a first change in tank level over
the first preset sampling time interval;
c. with the first change in tank level, calculating a first volume of fluid
collected over the first preset sampling time interval;
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d. receiving the speed signal to determine therewith a first pump speed;
e. with the first pump speed, the first volume, and the preset
manufacturer's pump rating value for the pump, calculating a first
pump efficiency value;
f. comparing the first pump efficiency value with the preset minimum
pump efficiency value.
g. and if the first pump efficiency value is equal to or greater than the
preset minimum pump efficiency value, increasing the pump speed by
the preset pump speed increment value,
h. and if the first pump efficiency value is less than the preset minimum
pump efficiency value, decreasing the pump speed toward the preset
minimum pump speed; and
i. and to repeat steps a) through h) at the end of each sampling time
interval thereafter;
j. and if the torque sensor registers a torque exceeding the preset
maximum torque setting, to override other functions to decrease the
speed of the pump by the preset pump speed increment value;
k. to repeat step j) at the end of each preset torque override bypass
slowdown time interval until:
i) the torque sensor registers a torque less than the preset
maximum torque setting and then return to step a); or
ii) the pump speed is reduced to zero.
100341 In some exemplary embodiments, step II h) includes decreasing the pump
speed by the
preset pump speed increment value.
100351 In yet another exemplary embodiment, there is provided a computer-
implemented method
of controlling an oil well, comprising:
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a. providing a progressive cavity pump in a well bore of the oil well;
b. providing a storage tank to receive fluid materials from the pump;
c. providing a pump drive section connected to the pump for delivering a drive
torque to drive
the pump at a corresponding pump speed:
d. configuring the pump drive section to receive instructions to increase
speed by one or more
preset pump speed increment values;
e. receiving signals from a tank level sensor and a speed sensor indicative of
tank level and
pump speed respectively;
f. receiving signals from a torque sensor indicative of the drive torque;
g. monitoring a pump efficiency value for changes in pump efficiency and to
vary the pump
speed according to the pump efficiency value, including:
1. receiving into memory:
a. a preset manufacturer's pump rating value for the pump;
b. a preset minimum pump efficiency value;
c. a preset pump speed increment value:
d. a preset sampling time interval for collecting data from the tank level
and speed sensors;
e. a preset maximum torque setting;
f. a preset torque override bypass slowdown time interval;
g. a preset minimum pump speed; and
h. a preset maximum pump speed;
11. and, after a first preset sampling time interval:
a. receiving the tank level signal and determining therewith a first tank
level;
b. with the first tank level, determining a first change in tank level over
the first preset sampling time interval;
c. with the first change in tank level, calculating a first volume of fluid
collected over the first preset sampling time interval;
CNR-MPF./CDA 17
CA 02686310 2009-11-25
d. receiving the speed signal to determine therewith a first pump speed;
e. with the first pump speed, the first volume, and the preset
manufacturer's pump rating value for the pump, calculating a first
pump efficiency value;
F. comparing the first pump efficiency value with the preset minimum
pump efficiency value;
g. and if the first pump efficiency value is equal to or greater than the
preset minimum pump efficiency value, increasing the pump speed by
the preset pump speed increment value ;
h. and if the first pump efficiency value is less than the preset minimum
pump efficiency value, decreasing the pump speed toward the preset
minimum pump speed; and
i. and to repeat steps a) through h) at the end of each sampling time
interval thereafter;
j. and, if the torque sensor registers a torque exceeding the preset
maximum torque setting, to override other functions to decrease the
speed of the pump to zero or to the preset minimum pump speed and to
maintain the pump at zero or at the preset minimum pump speed until
the torque sensor registers a torque less than the preset maximum
torque setting.
100361 In yet another exemplary embodiment, there is provided a computer-
implemented
method of controlling an oil well, comprising:
- receiving into memory:
- a preset minimum pump efficiency value;
- a preset pump speed increment value;
CNR-MPFICDA 18
CA 02686310 2009-11-25
- a preset sampling time interval for collecting data from a tank level sensor
indicative
of a level of oil fluid in a tank downstream from an oil pump in the oil well,
and data
from a speed sensor indicative of a pump speed of the pump;
- a preset maximum torque setting for torque to be delivered to the pump;
- a preset minimum pump speed;
- a preset maximum pump speed:; and
- a preset manufacturer's pump rating value for the pump;
and after a first operational time period:
- receiving a tank level signal from the tank level sensor and determining
therewith a
first tank level;
- with the first tank level, determining a first change in tank level over the
first preset
sampling time interval;
- with the first change in tank level, calculating a first volume of fluid
collected over
the first preset sampling time interval;
- receiving a speed signal from the speed sensor to determine therewith a
first pump
speed,
- with the first pump speed, the first volume, and the preset manufacturer's
pump
rating value for the pump, calculating a first pump efficiency value;
- comparing the first pump efficiency value with the preset minimum pump
efficiency
value;
- and if the first pump efficiency value is equal to or greater than the
preset minimum
pump efficiency value, signaling an increase in the pump speed by the preset
pump
speed increment value;
- and if the first pump efficiency value is less than the preset minimum pump
efficiency value, signaling a decrease in the pump speed toward the preset
minimum
pump speed; and
collecting data from a torque sensor indicative of torque being delivered to
the pump, and if the
torque sensor registers a torque exceeding the preset maximum torque setting,
overriding the
CNR-MPG/CDA 19
CA 02686310 2009-11-25
controller and signaling a decrease in the speed of the pump to zero or to the
preset minimum
pump speed.
100371 In yet another exemplary embodiment, there is provided a computer-
implemented method
of controlling an oil well, comprising:
- receiving into memory:
- a preset minimum pump efficiency value;
- a preset pump speed increment value;
- a preset sampling time interval for collecting data from a tank level
sensor, indicative
of a level of oil fluid in a tank downstream from an oil pump in the oil well
and data
from a speed sensor indicative of a pump speed of the pump;
- a preset maximum torque setting for torque to be delivered to the pump;
- a preset torque override bypass slowdown time interval;
- a preset minimum pump speed;
- a preset maximum pump speed; and
- a preset manufacturer's pump rating value for the pump;
- and, after a first preset sampling time interval:
- receiving a tank level signal from the tank level sensor and determining
therewith a
first tank level;
- with the first tank level, determining a first change in tank level over the
first preset
sampling time interval;
- with the first change in tank level, calculating a first volume of fluid
collected over
the first preset sampling time interval:
- receiving a speed signal from the speed sensor to determine therewith a
first pump
speed,
- with the first pump speed, the first volume, and the preset manufacturer's
pump
rating value for the pump, calculating a first pump efficiency value;
CNR-MPF/CDA 20
CA 02686310 2009-11-25
- comparing the first pump efficiency value with the preset minimum pump
efficiency
value;
- and if the first pump efficiency value is equal to or greater than the
preset minimum
pump efficiency value, signaling to increase the pump speed by the preset pump
speed
increment value;
- and if the first pump efficiency value is less than the preset minimum pump
efficiency value, signaling to decrease the pump speed toward the preset
minimum
pump speed; and
collecting data from a torque sensor indicative of torque being delivered to
the pump, and if the
torque sensor registers a torque exceeding the preset maximum torque setting,
overriding other
operations of the controller and signaling a decrease in the speed of the pump
to zero.
100381 1n yet another exemplary embodiment. there is provided a computer
readable medium
comprising computer-executable instructions for performing the method as
defined above. In this case, the
medium may include a data storage device such as a hard drive, a USB key,
thumb drive, computer
memory, a computer readable disk such as a Digital Video Disk (DVD) or the
like.
100391 In yet another exemplary embodiment, there is provided a system for the
recovery of oil
bearing fluid materials from an oil well, comprising a pump, and a storage
tank arranged to receive fluid
materials from the pump. A drive unit is connected to the pump for delivering
a drive torque thereto to
operate the pump at a corresponding operating speed. A controller is provided
for controlling the drive unit
and receiving signals from sensors. A tank level sensor is provided for
sensing the level of fluid in the
storage tank and is in communication with the controller for dispatching a
tank level signal representative
of the tank level. A speed sensor is provided for sensing the operating speed
of the pump and is in
communication with the controller for dispatching a speed signal
representative of the operating speed. A
torque sensor is provided for sensing the drive torque and is in communication
with the controller for
dispatching a torque signal representative of the drive torque. The controller
is configured to calculate, at
regular time intervals:
CNR-MPI:/C DA 21
CA 02686310 2009-11-25
- a volume of fluid collected during a regular time interval, according to
changes in the tank
level:
- a pump efficiency value according to the volume of fluid collected and the
speed of the
pump, and
- a pump efficiency ratio value according to the pump efficiency value and a
rated pump
efficiency value for the pump.
After calculating the pump efficiency ratio, the controller is further
configured to:
- increase the operating speed from a current operating speed toward a
predetermined
maximum operating speed, so long as the pump efficiency ratio equals or
exceeds a preset
minimum pump efficiency ratio value: or
- decrease the operating speed from the current operating speed toward a
predetermined
minimum operating speed, so long as the pump efficiency ratio does not exceed
a preset
minimum pump efficiency ratio value.
100401 In some exemplary embodiments, the controller is also configured to
receive the torque
signal and to determine a torque level for the pump. If the torque level
indicates that the pump is in an over
torque condition, the controller is configured to override all other
operations and to decrease the speed of
the pump from a current operating speed to a predetermined minimum operating
speed, or to zero,
regardless of a previously calculated pump efficiency ratio value.
100411 In some exemplary embodiments, the controller is configured to add an
operational
variance factor to the preset minimum pump efficiency value, the controller is
further configured to reduce
the pump speed by the preset pump speed increment value where, at the end of
any preset sampling time
interval, the calculated pump efficiency value is less than the preset minimum
pump efficiency value plus
the operational variance factor, but greater than the preset minimum pump
efficiency value, and the
controller further configured to reduce the pump speed to the preset minimum
pump speed where, at the
end of each of at least two consecutive preset sampling time intervals, the
calculated pump efficiency value
is less than the preset minimum pump efficiency value.
CNR-MPS:/CUA 22
CA 02686310 2009-11-25
100421 In some exemplary embodiments, the controller is configured to add an
operational
variance factor to the preset minimum pump efficiency value, the controller
further configured to make no
change to the pump speed where at the end of any preset sampling time interval
the calculated pump
efficiency value is less than the preset minimum pump efficiency value plus
the operational variance
factor, but greater than the preset minimum pump efficiency value, and the
controller further configured to
reduce the pump speed to the preset minimum pump speed where, at the end of
each of two consecutive
preset sampling time intervals, the calculated pump efficiency value is less
than the preset minimum pump
efficiency value.
100431 In yet another exemplary embodiment, there is provided a computer-
implemented
method of controlling an oil well, comprising:
a. providing a progressive cavity pump in a well bore of the oil well;
b. providing a storage tank to receive fluid materials from the pump;
c. providing a pump drive section connected to the pump for delivering a drive
torque to
drive the pump at a corresponding pump speed;
d. configuring the pump drive section to receive instructions to increase
speed by one or
more preset pump speed increment values;
e. receiving signals from a tank level sensor and a speed sensor indicative of
tank level and
pump speed respectively;
f. receiving signals from a torque sensor indicative of the drive torque;
g. monitoring a pump efficiency value for changes in pump efficiency and to
vary the pump
speed according to the pump efficiency value, including:
1. receiving into memory:
a. a preset manufacturer's pump rating value for the pump:
b. a preset minimum pump efficiency value;
c. a preset pump speed increment value;
d. a preset sampling time interval for collecting data from the tank level
and speed sensors;
CNR-MPL:/CD,~ 23
CA 02686310 2009-11-25
e. a preset maximum torque setting;
f. a preset torque override bypass slowdown time interval:
g. a preset minimum pump speed; and
h. a preset maximum pump speed;
II. and, after a first preset sampling time interval:
a. receiving the tank level signal and determining therewith a first tank
level,
b. with the first tank level, determining a first change in tank level over
the first preset sampling time interval;
c. with the first change in tank level, calculating a first volume of fluid
collected over the first preset sampling time interval;
d. receiving the speed signal to determine therewith a first pump speed;
e. with the first pump speed, the first volume, and the preset
manufacturer's pump rating value for the pump, calculating a first
pump efficiency value:
f. comparing the first pump efficiency value with the preset minimum
pump efficiency value;
g. and if the first pump efficiency value is equal to or greater than the
preset minimum pump efficiency value, increasing the pump speed by
the preset pump speed increment value:
h. and if the first pump efficiency value is less than the preset minimum
pump efficiency value, decreasing the pump speed toward the preset
minimum pump speed; and
i. and to repeat steps a) through h) at the end of each sampling time
interval thereafter:
j. and if the torque sensor registers a torque exceeding the preset
maximum torque setting, to override other functions of the control
CNR-MPL/CDA 24
CA 02686310 2009-11-25
system and to decrease the speed of the pump by the preset pump speed
increment value :,
k. to repeat step j) at the end of each preset torque override bypass
slowdown time interval until:
i) the torque sensor registers a torque less than the preset
maximum torque setting and then return to step a); or
ii) the pump speed is reduced to zero.
100441 Some exemplary embodiments further comprise, in section 1, receiving
into memory:
i. an operational variance factor,
and further comprise, in section 11 after step k:
1. if, at the end of a preset sampling time interval, the calculated pump
efficiency value is less than the preset minimum pump efficiency value
plus the operational variance factor, but greater than the preset
minimum pump efficiency value, decreasing the pump speed by the
preset pump speed increment value; and
in. if, at the end of a first preset sampling time interval, the calculated
pump efficiency value is less than the preset minimum pump
efficiency value, making no change to the pump speed; and
n. if, at the end of a second consecutive preset sampling time interval,
the calculated pump efficiency value is still less than the preset
minimum pump efficiency value, reducing the pump speed to the
preset minimum pump speed.
100451 Some exemplary embodiments further comprise, in section I, receiving
into memory:
i. an operational variance factor,
and further comprise, in section 11 after step k:
CN R-MPG/C DA ') 5
CA 02686310 2009-11-25
1. if, at the end of a preset sampling time interval, the calculated pump
efficiency value is less than the preset minimum pump efficiency value
plus the operational variance factor, but greater than the preset
minimum pump efficiency value, making no change to the pump speed;
and
M. if, at the end of a preset sampling time interval, the calculated pump
efficiency value is less than the preset minimum pump efficiency value
reducing the purnp speed to the preset minimum pump speed.
100461 Some exemplary embodiments further comprise, in section 1, receiving
into memory:
i. an operational variance factor,
and further comprise, in section II after step k:
1. if, at the end of a preset sampling time interval, the calculated pump
efficiency value is less than the preset minimum pump efficiency value
plus the operational variance factor, but greater than the preset
minimum pump efficiency value, making no change to the pump speed;
and
m. if, at the end of a first preset sampling time interval, the calculated
pump efficiency value is less than the preset minimum pump
efficiency value making no change to the pump speed; and
n. if, at the end of a second consecutive preset sampling time interval,
the calculated pump efficiency value is still less than the preset
minimum pump efficiency value, reducing the pump speed to the
preset minimum pump speed.
100471 Thus, in some exemplary embodiments, a system is provided which
maintains continuous
operation of a pump operating in a well bore of a well producing oil and
associated substances from an oil
bearing subterranean reservoir, while protecting the pump from excessive wear,
or seizing.
CNR-MPI:/CDA 26
CA 02686310 2009-11-25
BRIEF DESCRIPTION OF THE DRAWINGS
100481 Several preferred embodiments of the present invention will be
provided, by way of
examples only, with reference to the appended drawings, wherein;
100491 Figure l is a schematic view of a well installation; and
100501 Figures 2 and 3a to 3c are flow diagrams of a protocol for the
operation of the pump
comprising part of the well installation of figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
100511 It should be understood that the invention is not limited in its
application to the details of
construction and the arrangement of components set forth in the following
description or illustrated in the
drawings. The invention is capable of other embodiments and of being practiced
or of being carried out in
various ways. Also, it is to be understood that the phraseology and
terminology used herein is for the
purpose of description and should not be regarded as limiting. The use of
"including," "comprising," or
"having" and variations thereof herein is meant to encompass the items listed
thereafter and equivalents
thereof as well as additional items. Unless limited otherwise, the terms
"connected," "coupled," and
"mounted," and variations thereof herein are used broadly and encompass direct
and indirect connections,
couplings, and mountings. In addition, the terms "connected" and "coupled" and
variations thereof are not
restricted to physical or mechanical connections or couplings. Furthermore,
and as described in subsequent
paragraphs, the specific mechanical configurations illustrated in the drawings
are intended to exemplify
embodiments of the invention. However, other alternative mechanical
configurations are possible which
are considered to be within the teachings of the instant disclosure.
Furthermore, unless otherwise indicated,
the term "or" is to be considered inclusive. The term "a" when followed by a
single recitation of a named
feature is to be construed inclusively, to mean that it includes within its
meaning, more than one of the
named feature, or more than one feature including the named feature.
CNR-MPF./CDA 27
CA 02686310 2009-11-25
100521 Figure 1 illustrates, schematically, an oil recovery installation 10
comprised of a number
of individual oil well sites 12, which in this example, for the sake of
illustration, number three. That being
said, a typical oil recovery installation may involve an oil field with
hundreds of well sites 12. Each well
site 12 includes an oil well 14 which has been drilled from the surface into a
geological formation
containing oil bearing fluid materials, such oil well having with an inner
well bore 14a provided by a well
casing 16 extending into the ground and ending at or near a geological
formation 18 containing oil bearing
fluid materials. One such geological formation 18 is made up of an
unconsolidated sand matrix with oil
fluid (or fluids) contained in interstitial spaces or entrained with the sand
therein, though the devices and
methods disclosed herein may be applied to other geological formations, as
desired. The oil fluid drawn
from the oil well 14, of this example, will include an entrained sand
constituent, as well as brine and oil
emulsion contained in the geological formation. As entrained sand is carried
with oil fluid drawn from the
sand matrix, channels (known in the trade as "worm holes") tend to form and
interconnect outwardly from
the well bore and these will randomly widen, lengthen and join one another, as
a flow of oil fluid is first
formed in the matrix and then as oil fluid flows through these ever-changing
channels. As the channels
change, unconsolidated sand and other materials from the matrix are thus
further released into, and carried
with, the oil fluid flow.
100531 A progressive cavity pump 20 is located in the inner well bore 14a of
the oil well 14, with
an inlet portion 22 located down hole and an outlet portion 24 which is
joined, by way of a fluid line shown
at 26, to a storage tank 28. A drive train 30 including an hydraulic drive
head motor 32 mounted on top of
the well and connected mechanically to the pump 20 and a motive power source,
either electric, hydraulic
or mechanical. delivers a drive torque to drive the pump 20 at a corresponding
operating speed. In this
case, the drive train 30 is operable, in one operating phase, to vary (that
is, increase or decrease) the pump
speed by one or more preset pump speed increment values, and, in another
operating phase, to roll back the
pump speed. The drive train 30 is exemplified, in part, by the hydraulic drive
head motor 32, driven by an
hydraulic pump 34 via hydraulic fluid lines shown at 34a, 34b. In turn, the
hydraulic pump 34 is driven by
a drive motor 36, such as an internal combustion engine, an electrical motor
or the like. The drive train 30
in turn communicates with a controller shown at 38 via data path 36a.
C NR-MPE/CDA 28
CA 02686310 2009-11-25
100541 The progressive cavity pump includes a rotor portion 20a with a helical
shaped section
set within a housing lined with an elastomer in which is formed a mirror image
of the helical section of the
rotor, and acts as a stator portion 20b. The stator portion 20b thus offsets
the helical shaped rotor portion
of rotor 20a, so that the engagement of the rotor and stator portions 20a, 20b
by rotating the rotor forms a
series of helical cavities between the stator portion 20b and the helical
section of the rotor portion 20a.
Rotation of the rotor portion 20a, relative to the stator portion 20b in one
direction, therefore causes the oil
fluid in the cavities to progress upwardly from the inlet portion 22 to the
outlet portion 24. To maintain an
effective seal in the helical cavity, it is necessary that an effective seal
be established between the helical
sections of the rotor portion 20a and stator portion 20b, which is typically
provided by low friction
materials on one or both thereof. The presence of sand in the oil fluid
increases friction between the rotor
and stator portions 20a, 20b which increases the torque needed to continue
operation of the pump.
100551 The controller 38 is provided for controlling the drive train 30 in
response to changes in
pump efficiency, as will be described below. In this case, the controller 38
includes a computer screen, a
keyboard or keypad, one or more processors, for example one or more
programmable logic controllers
(PLC's) 40, one or more hard drives, as well as one or more memory chips, and
one or more network
interface ports, as needed, to couple with data paths 36a, 48a, 50a and 52a
(as will be described below).
The controller 38 is part of a communication network 42, such as the Internet
or a configured intranet, via
data path 38a in order to communicate with a central station shown at 44. The
controller 38, the
communication network 42 and the central station 44 may be part of a larger
oil field control system, such
as that well known as Supervisory Control and Data Acquisition or SCADA.
100561 The controller 38 may, alternatively, be computer implemented in a
number of forms, by
way of one or more software programs configured to run on one or more general
purpose computers, such
as a personal computer. The system may, alternatively, be executed on a more
substantial computer
mainframe. The general purpose computer may work within a network involving
several general purpose
computers, for example those sold under the trade names APPLE or IBM, or
clones thereof, which are
programmed with operating systems known by the trade names WINDOWS, LINUX or
other well known
CNR-MPFICL)n 29
CA 02686310 2009-11-25
or lesser known equivalents of these. The system may involve pre-programmed
software using a number
of possible languages or a custom designed version of a programming software.
The computer network
may be include a wired local area network, or a wide area network such as the
Internet, or a combination of
the two, with or without added security, authentication protocols, or under
"peer-to-peer" or "client-server"
or other networking architectures. The network may also be a wireless network
or a combination of wired
and wireless networks. The wireless network may operate under frequencies such
as those dubbed `radio
frequency' or "RF" using protocols such as the 802.1 1, TCP/IP, BLUE TOOTH and
the like, or other well
known Internet, wireless, satellite or cell packet protocols.
10057 A graphical user interface (GUI) 46 is also provided to allow for local
programming and
for setting of default values for the operation of controller 38, via data
path 46a. The GUI 46 may include a
computer implemented terminal interface, with a computer screen, a keyboard or
keypad, one or more
processors, memory, one or more hard drives and network interface ports or the
like as required to allow
for communication between the GUI 46 and the controller 38, for inputting data
and for making user
settings. Alternatively, the GUI 46 may take the form of a software
application running on a general
purpose computer which, via one or more remote telemetry protocols, provides
remote communication with
and control of the controller 38.
100581 The storage tank 28 is provided with a tank level sensor 48 for sensing
the level of fluid
therein. In this case, the tank level sensor is a pressure sensor, such as
that commercially available under
the trade name FOXBORO by INVENSYS PROCESS SYSTEMS. The tank level sensor is
in
communication with the controller 38 via data path 48a for dispatching a tank
level signal representative of
the tank level, in other words the height of the fluid in the storage tank. In
this case, the tank is shown to be
partially filled with oil fluid which has separated out by dens ity/specif ic
gravity, with the lowermost layer
containing the sand and other relatively dense constituents. A central layer
includes the groundwater
constituent while the upper layer contains the oil constituent. In this case,
the tank level sensor is located
generally in the lower portion of the upper layer so as to monitor tank levels
in the upper layer, though the
('NR-MPP,/CDA 30
CA 02686310 2009-11-25
sensor may be placed at other elevations as desired. Other techniques to
measure tank level may also be
used as desired.
100591 A speed sensor 50 is also provided on drive train 30, for sensing the
operating speed of
the pump 20 by measuring the flow of hydraulic fluid in the hydraulic supply
line 34a. One example of the
speed sensor is commercially available under the trade name BLANCETT TURBINE
FLOW METER by
RACINE FEDERATED INC. The speed sensor 50 is in communication with the
controller 38, via data
path 50a, for dispatching a signal representative of the flow of hydraulic
fluid to the drive head 32, for
conversion to a quantity which is representative of pump speed in revolutions
per minute. Alternatively,
the speed sensor 50 may include a processing function to calculate the pump
speed and to dispatch a pump
speed signal to the controller 38. Other speed sensors may be used as desired.
100601 A torque sensor 52 is also provided on the drive train 30 for sensing
the drive torque
exerted on the pump 20 by measuring the supply pressure in the hydraulic
supply line 34a. One example
of the torque sensor is commercially available under the trade name ECO I by
WIKA INSTRUMENT
CORPORATION. The torque sensor 52 is in communication with the controller 38,
via data path 52a, for
dispatching a signal representative of the pressure in hydraulic supply line
34a, for conversion to a quantity
which is representative of the drive torque. In this case, the controller 38
is operable to detect increases in
torque by fluctuations in the hydraulic supply pressure. Alternatively, the
torque sensor 52 may include a
processing function to calculate the drive torque and to dispatch a drive
torque signal to the controller 38.
In this case, the drive torque is one example of a load being exerted on, or
being generated by, the pump 20.
Other loads may be also be monitored, as represented by heat, pressure, strain
and the like.
100611 The controller 38 is configured to carry out a pump monitoring and
control protocol
based on a pump efficiency value, where changes in pump speed are made
according to pump efficiency.
Each pump is provided with a rating by the manufacturer that specifies a
volume of fluid that can be
produced by the pump at a specified pump speed (in this case in RPM) over a
specified period of time
under ideal conditions. This manufacturer's pump rating value is deemed to
represent an ideal 100%
CNR-MPE/CDA 31
CA 02686310 2010-11-04
efficiency value for the pump. Measured pump efficiency is thus calculated
against this ideal efficiency
value and is determined by the formula: PE _ [(Vt / St)/(Vr/Sr)] 100, where:
Vt is the volume of fluid collected in the tank 28 in a predetermined sampling
time
interval, adjusted to a 24 hour period;
St is pump speed during the predetermined sampling time interval, expressed in
RPM;
Vr is a rating provided by the manufacturer for a volume of fluid produced in
a
rated time interval, adjusted to a 24 hour period; and
Sr is the manufacturer's rated pump speed, expressed in RPM required to
produce
Vr.
100621 Thus, in one example, the performance of the pump 20 is measured by a
calculation of
volume of oil fluid pumped during a particular sampling time period, such as a
one hour period, at a
measured pump speed and then converted to an effective volume of oil fluid
pumped over a 24 hour period,
which is then compared against the manufacturer's rating value for the pump
and expressed as a
percentage. This formula thus measures the performance of the pump, as an
efficiency value based on its
actual performance against its manufacturer's rating value which is deemed to
be the point at which the
pump 20 is operating at 100 percent efficiency. Other sampling time intervals
may be used as desired.
100631 An aim of this protocol is to maximize the flow of oil fluid per pump
revolution.
Maximizing the "flow of oil fluid per pump revolution" does not necessarily
mean operating the pump at
maximum speed. "As the rotor turns inside the stator, fluid moves through the
pump from cavity to cavity.
As one cavity diminishes, the opposing cavity increases at exactly the same
rate which results in a
pulsationless positive displacement flow through the pump. The cavities are
separated from each other by a
series of seal lines which are created between the rotor and stator." (SPE
paper #37455 Progressive
Cavity(PC) Pump Design Optimization for Abrasive Applications) Seeking to
maximize the gross flow of
oil fluid in a given time frame may result, in some cases, in a reduction in
the amount of fluid produced per
pump revolution. This can in
CNR-MPE/CDA 32
CA 02686310 2009-11-25
turn lead to premature wear or damage to the pump and result in inefficient
operation of the pump. As the
fluid being pumped from an oil bearing unconsolidated sand reservoir carries
abrasive materials in the
form of fine sand in varying quantities, higher pump speeds, although they may
temporarily translate into
higher total volumes of fluid produced, may result in more rapid wear of the
pump and more frequent need
to service and replace the pump. "Abrasive wear of progressive cavity pumps is
one of the most common
modes of failure. High speed particles (sand) traveling through pump cavities
abrade both rotor and stator.
This causes the seal lines between the rotor and stator to become less
effective and results in higher pump
slippage. The increase in the pump slippage will reduce pump volumetric
efficiency and will gradually
destroy the pump" (SPE paper #37455 Progressive Cavity(PC) Pump Design
Optimization for Abrasive
Applications). Therefore, by focusing on volume of fluid produced per unit
speed (in this case RPM) or
pump efficiency, pump wear caused by operation at excessive pump speeds may be
detected much more
readily and rapidly than by focusing on gross volume of fluid produced over
time.
100641 Therefore, the operational life of the pump may be extended to reduce
the frequency and
duration of time that the pump has to be stopped, removed, repaired or
replaced. Thus, in this case, a
degree of protection is afforded the pump to reduce the rate of wear and the
frequency of breakdown, while
preserving and maintaining continuous operation of the pump for a relatively
longer period of time in order
to maximize and maintain the growth of the channels developed in the reservoir
resulting from the
continuous production of sand with the fluid produced by pumping such fluid
from the reservoir.
100651 Another feature in the exemplified protocol of the controller 38 (as
will be described
more fully below) is the detection of pump-off conditions and the reduction in
the risk of pump-off
conditions occurring. For detecting pump off, monitoring pump efficiency is at
least as effective as
monitoring volume of fluid produced over time. However, as an embodiment of
the exemplified protocol is
the operation of the pump at a lower RPM setting than would otherwise occur if
the pump were operated to
maximize gross production over time, the likelihood of pump-off occurring is
greatly reduced.
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100661 Another feature in the exemplified protocol of the controller 38 is the
sensing of torque,
and the implementation of a speed reduction procedure, as an override to the
other monitoring and speed
varying functions of the controller 38, in high torque (or as is known in the
art as "over torque") conditions.
The sensing of torque, in this example, is a function which operates
independently of, and concurrently
with, other monitoring functions of the controller and implements an override
response to over torque
conditions to minimize catastrophic pump damage or seizing of the pump.
However, as an embodiment of
the exemplified protocol is the operation of the pump at a lower speed setting
than would otherwise occur
if the pump were operated to maximize gross production over time, the
likelihood of an over torque
condition occurring is greatly reduced.
100671 Thus, as will be described, the exemplified protocol provides for a
threshold pump
efficiency value, above which the pump speed is increased toward a maximum
pump speed setting and
below which the pump speed is decreased toward a minimum pump speed. In some
cases, the threshold
pump efficiency value may take into account a minimum pump efficiency plus an
additional operational
variance factor, such as 10 percent, to increase the sensitivity of the
controller 38 to negative changes in
pump efficiency and thus increase the likelihood that the decreasing of the
pump speed occurs before pump
efficiency falls to or below the acceptable minimum pump efficiency. Since
pump wear, when pumping
fluid carrying abrasives, may be directly correlated to pump speed, decreasing
pump speed sooner when
pump efficiency is falling is believed to help minimize pump damage. With the
use of the operational
variance factor, increases in pump speed may not occur immediately after
minimum pump efficiency is
reached, thus allowing for changes in operating conditions such as sudden
variations in sand, water or gas
volumes being carried in the fluid being produced by the pump to stabilize or
pass before increasing pump
speed. The appearance of these conditions may dramatically change pump
efficiency within the sampling
time interval. Such conditions are often characteristic of situations giving
rise to over torque, pump off or a
dramatic drop in pump efficiency.
100681 With these operating principles in inind, reference may be made to
figures 2 and 3a to 3c
showing representations of an exemplified operation of the pump monitoring and
control protocol carried
('NR-MP[/C'Di .34
CA 02686310 2009-11-25
out by the controller 38. At step 100, the user sets the controller to manual
mode and then, at step 102,
configures the controller 38 for a particular well site 12 by entering,
directly or indirectly, the following
data via the GUI 46.
OPERATOR INPUT:
- MAXIMUM PUMP SPEED
- MINIMUM PUMP SPEED
- MAXIMUM TORQUE ALLOWED
- MINIMUM PUMP EFFICIENCY
- OPERATIONAL VARIANCE FACTOR
SAMPLING TIME INTERVAL
PUMP SPEED INCREASE/DECREASE INCREMENT
PUMP SIZE in M3/Day @ 100 RPM = MANUFACTURER'S PUMP RATING VALUE
HYDRAULICS BYPASS SLOWDOWN TIME INTERVAL
100691 The MAXIMUM PUMP SPEED, in one example, is set to the manufacturer's
rated
maximum pump speed for a selected pump, while the MINIMUM PUMP SPEED is
selected to maintain a
minimum recovery flow of oil bearing fluid from the geological formation in
order to preserve and
continuously grow the network of channels and wormholes therein. The
HYDRAULICS BYPASS
SLOWDOWN TIME INTERVAL is smaller than the SAMPLING TIME INTERVAL and is
provided to
make pump speed adjustments more rapidly or frequently due to the increased
potential of pump lock up
and/or damage when over torque conditions occur. One or more of these input
settings may be provided
either in a dedicated data field in an input screen or be provided in a drop
down menu format. For instance,
the GUI 46 may provide a drop down menu of pump types and manufactures to
provide automatically the
value for PUMP SIZE in M3/Day a, 100 RPM.
100701 It will be noted that, in this example, the controller 38 stores one
PUMP SPEED
INCREASE/DECREASE INCREMENT value. However, the system may be configured to
store more
CNR-MPIE/CI)A 35
CA 02686310 2009-11-25
than one increment value for different phases in the operation of the
controller 38. For instance, a larger
increment value may be provided for a PUMP SPEED DECREASE INCREMENT value, and
a relatively
smaller increment value may be provided for a PUMP SPEED INCREASE INCREMENT
value, or vice
versa.
100711 It will also be noted that the OPERATIONAL VARIANCE FACTOR may be
preselected
and inputted into the controller 38 as part of the algorithmic programming of
controller 38. Hereafter, the
term PUMP EFFICIENCY THRESHOLD shall refer to the MINIMUM PUMP EFFICIENCY plus
the
OPERATIONAL VARIANCE FACTOR. If desired, the minimum pump efficiency may be
used as the
pump efficiency threshold in the absence of an operational variance factor.
100721 The following is a listing of the operator inputs for an exemplified
well site 12:
- MAXIMUM PUMP SPEED: 150 RPM
- MINIMUM PUMP SPEED : 30 RPM,
- MAXIMUM TORQUE ALLOWED: 2500 PSI
- MINIMUM PUMP EFFICIENCY : 40 PERCENT
- OPERATIONAL VARIANCE FACTOR: 110 PERCENT
- SAMPLING TIME INTERVAL: 1 HOUR
- PUMP SPEED INCREASE/DECREASE INCREMENT: 5 RPM
- PUMP SIZE in M3/Day @ 100 RPM: 15m3/day @ 100 RPM
- BYPASS SLOWDOWN TIME INTERVAL: 15 MINUTES
PUMP START UP:
100731 Thus, at step 104, the operator turns on the pump to a selected startup
pump speed, for
example 50 RPM.
100741 There are a number of diagnostic checks that are carried out in the
manual mode, which
may be done manually by the field operator, or in an automated fashion, or be
a combination of both. For
CNR-MPE/CDA 36
CA 02686310 2009-11-25
instance, if the well site 12 is already being managed by a control and
management system such as
SCADA, then a number of number of diagnostic checks may be done on a range of
conditions such as
operating temperatures of different components of the pump and drive train,
the condition of the hydraulic
pump and drive motor, all with the aim of verifying that the startup
conditions of the pump and drive train
are normal. Alternatively, the controller 38 may carry out selected diagnostic
functions independent of the
SCADA management system, in which case the initial diagnostic functions may in
some instances include
an initial torque sensing function as described below.
100751 When the manual mode steps are complete, the operator then, at step
105, switches the
pump 20 to the automatic mode, which proceeds to steps 106, 108 and 1 10, in
which the controller 38
begins a continuous monitoring of pump speed, checks the tank level sensor for
a baseline measurement
and initiates the time count for the first sampling time interval. While steps
106, 108, 110 are shown to
occur simultaneously, the steps may also be executed, in some cases,
consecutively according to a specific
programming sequence in the controller 38. The controller 38 advances then to
step 112 at the end of the
first sampling time interval and then to step 114 where the controller 38
samples tank level.
100761 The controller advances to step 1 16 to determine if the change in tank
level is positive. If
NO, the controller initiates a time count, at step 118, for a next sampling
time interval. If YES, the
controller calculates, at step 120, pump efficiency PE according to the
formula above. A "NO" condition
would occur if the tank 28 has been emptied or partially drained in order to
transport fluid produced from
well site 12 to a cleaning plant for processing.
100771 At step 120 the controller 38 calculates the measured pump efficiency
by:
= First, calculating the volume of fluid produced during the sampling time
interval based on
the change in tank level from the beginning of the sampling time interval to
the end of
such interval and grossing this up to a volume fluid produced over 24 hours;
= Second, noting the pump speed that the pump was operating at during the
sampling time
interval; and
C NR-MP[/CDA 37
CA 02686310 2009-11-25
= Third, comparing the calculated grossed up volume of fluid produced during
such interval
as a ratio over the pump speed noted for such interval, against the pump
manufacturer's
rated volume of fluid produced over the rated pump speed and expressing the
calculated
grossed up volume of fluid produced during such interval as a ratio over the
RPM noted
for such interval as a percentage of the pump manufacturer's rated volume of
fluid
produced over the rated pump speed.
100781 At step 122, the controller 38 compares the calculated pump efficiency
against the preset
PUMP EFFICIENCY THRESHOLD value. If the calculated pump efficiency is NOT LESS
than the preset
PUMP EFFICIENCY THRESHOLD value, the controller 38 advances to step 124 and to
determine if the
measured pump speed is matches the preset MAXIMUM PUMP SPEED value. If NO, the
controller
advances to step 126 and increases the pump speed by the PUMP SPEED
INCREASE/DECREASE
INCREMENT value. The controller 38 then advances to step 1 18 to initiate the
time count for the next
sampling time interval.
100791 Referring once again to step 124, if the calculated pump efficiency is
found to match the
preset MAXIMUM PUMP SPEED value, the controller 38 advances directly to step
118 to initiate the time
count for the next sampling time interval.
100801 Referring once again to step 122, if the calculated pump efficiency is
LESS than the
preset PUMP EFFICIENCY THRESHOLD value, the controller 38 advances to step 128
to determine if
the calculated pump efficiency is LESS than the preset MINIMUM PUMP EFFICIENCY
value. If NO,
the controller advances to step 130 to determine if the measured pump speed is
equal to the preset
MINIMUM PUMP SPEED value. If NO, the controller advances to step 131 to
decrease the pump speed
by the PUMP SPEED INCREASE/DECREASE INCREMENT value. The controller then
advances to step
118 to initiate the next sampling time interval.
CNR-MP[/CDA 38
CA 02686310 2009-11-25
10081 On the other hand, if, at step 128 the calculated pump efficiency is
indeed LESS than the
preset MINIMUM PUMP EFFICIENCY value, the controller proceeds to step 132 to
determine if, for the
immediately previous sampling time interval, the calculated pump efficiency
was also LESS than the preset
MINIMUM PUMP EFFICIENCY value. If NO, then the controller advances to step 118
to initiate the
time count for the next sampling time interval. If YES, the controller
proceeds to step 134 to implement a
roll back of the pump speed to the preset MINIMUM PUMP SPEED value and then,
at step 136, issues an
ALARM. The roll back at step 123 is not, in one example, an incremented
decrease but rather an
immediate slow down response, to permit the system to slow down to the MINIMUM
PUMP SPEED
value. Other slowdown procedures may also be implemented in this step, as
desired.
100821 Referring once again to the SET AUTO MODE step 105, this action also
initiates a
continuous torque monitoring subroutine beginning with step 140 in which the
controller collects signals
from the torque sensor and, at step 142, compares the a measured torque value
against the preset
MAXIMUM TORQUE ALLOWED value. If the measured torque exceeds the preset value,
an overtorque
condition is present and the controller 38 proceeds to steps 144, 146 and 148
at the same time. While steps
144, 146 and 148 are shown to occur simultaneously, the steps may also be
executed, in some cases,
consecutively according to a specific programming sequence in the controller
38. At step 144, the
controller issues an ALARM and an OVERRIDE of the other parallel active
subroutines along the various
paths following the END TIME INTERVAL STEP 112. At step 148, the controller
determines if the
measured pump speed is equal to the preset MINIMUM PUMP SPEED value. If NO,
the controller
advances to step 152 to decrease the pump speed by the PUMP SPEED
INCREASE/DECREASE
INCREMENT value. If YES, the controller advances to step 154 to maintain pump
speed. At step 146, the
controller initiates a bypass time count for the duration of the preset BYPASS
SLOWDOWN TIME
INTERVAL value, the end of which is marked at step 150. The controller then
advances to step 140 to
monitor torque and repeats the foregoing sequence.
100831 Alternatively, at step 148, the controller determines if the measured
pump speed is equal
to zero. If NO, the controller advances to step 152 to decrease the pump speed
by the PUMP SPEED
(. NR-MPE/C'I)A 39
CA 02686310 2009-11-25
INCREASE/DECREASE INCREMENT value. If YES, the controller advances to step 154
to maintain
pump speed at zero. In this case, the duration of this zero condition may be
relatively short, and terminate
when relatively swift remedial action is taken to rectify the overtorque
condition. This may involve
personnel in a control room receiving the alarm signal issued at step 144 and
reverting the system to a
manual condition for further remedial action, to remove sand from the pump,
such as by flushing or the
like. This condition provides the benefit of shutting down the pump
temporarily before it becomes
damaged and is meant to avoid long term shutdown and repair procedures.
100841 Thus, in one example, at the end of the first hour of operation (step
112), the controller 38
checks the tank level sensor reading (step 114), and using this reading
calculates the volume of production
that has flowed into the tank over that hour, and using the result of that
calculation, calculate the pump
efficiency (step 120) as a percentage of the "ideal" efficiency (which is
based on the manufacturer's design
efficiency for the pump).
100851 In the exemplified protocol of the controller 38, the maximum pump
efficiency calculated
is given an additional safety factor, in one example 10 percent, though
additional operational factor values
may be used as desired. In the exemplified protocol of the controller 38, if
the calculated efficiency is an
amount which is equal to or greater than 10% above the minimum pump efficiency
set by the operator (step
122) (example: if the preset minimum efficiency is 40% and the calculated
efficiency at the end of the first
hour must be 50% or better), the controller increases the speed of the pump
(step 126) by the amount of
RPM increment previously set by the operator (example 5 RPM) after determining
that the pump speed is
not yet equal to the preset maximum pump speed.
100861 If the calculated efficiency is an amount which is less than 10% above
the minimum
pump efficiency set by the operator, the controller 38 reduces the speed of
the pump 20 (step 131) by the
amount of RPM increment previously set by the operator.
CNR-MPUCDA 40
CA 02686310 2009-11-25
100871 At the end of the second hour of operation and at the end of every hour
thereafter the
controller 38 repeats the process set out above.
100881 Thus, at the end of each sampling time interval, as long as the
calculated efficiency
determined at the end of such hour is an amount which is equal to or greater
than 10% above the minimum
pump efficiency set by the operator, the controller 38 increases the speed of
the pump by the amount of
RPM increment previously set by the operator, even if the calculated
efficiency at the end of a sampling
time interval is less than, greater than or equal to the pump efficiency
calculated the immediately previous
hour.
100891 Provided however, if at the end of any hour the calculated efficiency
is an amount which
is less than the minimum pump efficiency set by the operator (step 128), the
controller quickly rolls back
the pump speed to the preset minimum pump speed (step 134) and then issue an
alarm (step 136).
100901 In other words, in an example, the controller keeps increasing the
speed of the pump each
hour (step 126) unless/until the calculated pump efficiency is less than 10%
above the minimum pump
efficiency set by the operator or the pump reaches its maximum RPM setting.
While other examples may
involve other speed control protocols, in this example, the only time periods
in which the controller holds
the RPM setting constant for any period of time over one hour is when:
- The controller 38 detects that the level of fluid in the tank has fallen to
a level which is lower
than the previous hour (step 116) (which indicates that the tank was emptied,
in which case
the controller 38 skips the process for that interval and waits until the end
of the next
sampling interval comes up to perform an efficiency calculation);
- The controller 38 detects an over torque situation (step 142) in which case
it reduces the
pump speed continuously in a series of steps down to the minimum RPM setting
(or zero
RPM setting) if necessary and if it has to reduce speed to the minimum RPM
setting the
CNR-MPtr''CDA 41
CA 02686310 2009-11-25
controller 38 holds the pump 20 at that speed until an operator attends to
check on the
problem;
- The controller has increased the pump speed to the preset maximum RPM
setting (step 124),
in which case it holds at that point unless pump efficiency falls below 10%
above the
minimum pump efficiency set by the operator or an over torque condition
occurs; or
- The controller has reduced pump speed to the minimum RPM setting as a result
of measured
pump efficiency falling below the preset minimum pump efficiency for two
consecutive
sampling time intervals, in which case the controller holds the pump at such
minimum RPM
setting until pump efficiency increases above the pump efficiency threshold
(which is
minimum pump efficiency plus the operational variance).
100911 In other exemplary embodiments, it may be desirable, in some examples,
not to use an
operational variance factor, in which case the protocol employed with
controller 38 may require that:
= the pump speed be increased by the preset pump speed increase increment if
the
measured pump efficiency at the end of the sampling time interval is greater
than or equal
to the minimum pump efficiency set by the operator, unless the pump is already
operating at the preset maximum pump speed, and
= the pump speed be decreased to the preset minimum pump speed if the measured
pump
efficiency at the end of the sampling time interval is less than the minimum
pump
efficiency set by the operator, unless the pump is already operating at the
preset minimum
pump speed.
TORQUE OVERRIDE:
100921 In one example, the pump controller 38 continuously monitors the torque
and RPM of the
pump and if the maximum torque limit is reached (step 142), the controller
reduces the RPM of the pump
down by the amount of the RPM increase/decrease increment previously set by
the operator (eg. 5 rpm)
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CA 02686310 2009-11-25
until the high torque situation has fallen below the preset maximum torque
limit (NOTE: the controller
does not, in this case, reduce RPM below the previously set minimum RPM
setting), though other speed
settings may be employed in other cases. Thus, in this example, the controller
38 makes changes to the
pump speed at the time intervals specified by the operator in setting the
Hydraulics Bypass Slowdown
Time. After the torque has fallen below the maximum torque setting, the
controller returns the pump to
normal automatic operation by initiating the time count procedure at 110, and
following through to step 112
and the steps which follow. Torque control, in this example, is configured to
dominate and override other
functions of the controller 38. However, there may be other examples in which
the torque monitoring
function is not continuous but rather carried out after preset torque
monitoring intervals. In some cases, the
torque monitoring functions may not override other functions of the system but
instead permit other
functions to continue operating but under conditions that preserve minimum
operations while minimizing
potential damage both to the pump and the geological formation. Thus, as can
be seen, the aim of the
controller 38 and its protocol as discussed in the exemplified methods above,
is to protect the pump from
wearing out prematurely and keep it in operation, while minimizing pump shut
down or break down.
100931 Thus, the system 10 is believed to provide an improved method of
optimizing a oil well
in an unconsolidated sand reservoir by maximizing the amount of oil produced
over the life of the well by
maximizing the amount of oil produced per unit speed of the pump, in this case
per unit RPM, as opposed
to simply maximizing the volume of fluid produced over a given time interval.
Further, it is believed that
efficiency of the pump expressed as actual volume of fluid produced per
revolution of the pump is a more
precise measure to use in managing the operation of the pump. Volume of
production per revolution of the
pump, when producing a fluid carrying an abrasive, translates into a useful
measure of the stress on the
pump components as a result of friction caused by the abrasive. Running the
pump faster may result in a
greater volume of fluid being produced in a given time interval. However, at
higher RPM's, if the volume
of fluid produced per revolution of the pump is low, the pump is encountering
greater friction and therefore
experiencing greater wear. Further, the system 10 is beneficial in reducing
the risk of, if not avoiding,
damage and potential seizing of the pump during operation, by detecting an
over torque situation and
C NR-MPE/CDA 43
CA 02686310 2010-11-04
promptly slowing the pump down to allow the higher concentration of sand to be
moved through and
cleared from the pump gently.
100941 While the pump 20 has been described as a progressive cavity pump,
other pumps may
also be employed including beam pumps and the like.
100951 While the present invention has been described for what are presently
considered the
preferred embodiments, the invention is not so limited. To the contrary, the
invention is intended to cover
various modifications and equivalent arrangements included within the spirit
and scope of the appended
claims. The scope of the following claims is to be accorded the broadest
interpretation so as to encompass
all such modifications and equivalent structures and functions.
CNR-MPE/CDA 44
