Note: Descriptions are shown in the official language in which they were submitted.
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Description
Method for determining operating properties of a drill-rod
borehole pump, and pump system for same
The invention relates to a method for determining operating
properties of a drill-rod borehole pump, comprising a pump head
which is connected to a kinematics converter via a drill rod,
and the kinematics converter is driven by an electric motor.
In addition, the invention relates to a pump system with a drill-
rod borehole pump, comprising a pump head which is connected to
a kinematics converter via a drill rod, and the kinematics
converter is driven by an electric motor.
The invention further relates to a computer-implemented method
for determining operating properties of a drill-rod borehole
pump.
Borehole pumps are used as delivery means to extract liquids
stored underground when the reservoir pressure is not sufficient
for them to reach the surface on their own or in sufficient
quantities. In most cases, they are used to extract crude oil.
Other fields of application include the pumping of brine and
medicinal waters.
The image of most oil fields is dominated by drill-rod borehole
pumps, which are also called horse-head pumps, nodding donkeys
or donkey pumps because of their appearance and movement. Here,
the actual pumping mechanism - a piston with check valves - is
arranged in a separate pipe string in the borehole near the oil-
bearing layer. The piston is set into a continuous up-and-down
motion by means of a screwable rod from a pump jack located at
the earth's surface. This is accomplished by the so-called horse
head. This consists of a circular arc segment arranged as a
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balancer, at the end of which a steel cable pair or chain pair
is clamped at the top.
The drive is mostly electric. However, in the presence of
sufficient energy-containing gases dissolved in the crude oil,
part of these gases can be separated from the pumped material
on site by means of a degasser and fed to a gas engine that
drives the pump.
Depending on the pump design and size, the working stroke is 1
to 5 m. Two and a half to twelve strokes per minute are common.
The drill-rod borehole pump can be used economically up to
pumping depths of around 2500 m. For greater depths, other pump
systems are more suitable due to the large weight of the liquid
column to be lifted.
The "Mark II" pump type from the Texan manufacturer Lufkin
Industries is particularly suitable for high delivery rates from
great depths due to its special movement geometry.
The "Sucker Rod" pump type has a sucker rod, which is a steel
rod typically between 25 and 30 feet long and threaded at both
ends, used in the oil industry to connect the surface and
borehole components of a reciprocating pump installed in an oil
well.
An extremely valuable tool for analyzing borehole performance
is a borehole test rig, which measures the load on the polished
rod in relation to the position of the polished rod.
Dynamometers can be used to record rod position and rod load
over time. The load-measuring part of the dynamometer is
attached to the polished rod so that the load can be measured
and sent to a recorder. An accompanying part of the dynamometer
attached to the lifting beam measures the position of the
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polished rod and sends it to the same recorder. The graph
produced is called a dynagraph, or more commonly a dynamometer
or dynagraph map, and corresponds to a load-displacement graph.
Dynamometer maps taken at the surface can rarely be used directly
to measure the operating conditions of the borehole pump, since
they also reflect all forces (static and dynamic) that occur
from the pump to the borehole head. However, if a dynamometer
is located directly above the pump, the recorded map is a true
indicator of pump operation. Gilbert's dynagraph (a mechanical
dynamometer) accomplished this in the 1930s. Rod loads directly
above the pump, recorded as a function of pump position, give
dynagraph maps a name that distinguishes them from surface maps.
Although the use of Gilbert's dynagraph allowed direct
investigation of pumping problems, the practical implications
associated with the need to run the instrument in the borehole
far outweighed its advantages.
Up to now, sensors have been used to measure the operating
conditions of a drill-rod borehole pump, and these sensors
measure the acting forces or the current position (inclination)
of the beam (also known as the crank arm), for example by means
of force sensors, Hall sensors or proximity sensors. From this,
the position of the drill rod is calculated. However, it is
time-consuming to calibrate the various sensors with each other.
In addition, inaccurate calibration can lead to errors that may
have an unfavorable influence on the evaluation of the
measurement data.
It is the object of the invention to provide a method and a
device for determining the operating properties of a drill-rod
borehole pump, which simplifies the measurement of the operating
conditions, whilst at the same time the measurement data are
measured more accurately than is known in the prior art.
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The object according to the invention is achieved by a method
of the kind mentioned at the outset, wherein a measuring means
is further provided for measuring the power consumption of the
motor during operation of same, said method comprising the steps
of:
a) measuring the current consumption and the operating
voltage of the motor in the form of discrete measuring
points over at least one pump cycle, with which four
operating phases of the borehole pump can be associated
in each case, and determining the power consumption of
the motor therefrom,
b) determining, for one pump cycle, a period and a maximum
of the power consumption that corresponds to the torque
maximum of the borehole pump,
c) determining a reference phase angle for the kinematics
converter with the aid of the properties of the
kinematics converter and the power consumption of the
motor, which reference phase angle describes the
relationship between the maximum of the power
consumption and the maximum of the force acting on the
drill rod of the borehole pump,
d) ascertaining a torque curve from the power consumption
of the motor with the aid of the properties of the
kinematics converter,
e) determining the operating properties of the delivery
pump from the torque curve ascertained in step d) using
the period determined in step b) and the reference phase
angle determined in step c).
The invention recognizes that the operating properties of the
delivery pump can also be ascertained without considering the
motor speed. The invention is based here on the surprising
realization that the operating properties of the delivery pump
can also be ascertained by the torque curve, the period and the
reference phase angle.
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This means that no further sensors, which have to be attached
to the pump, are required to determine the operating properties
of the delivery pump.
Furthermore, a complex calibration of such sensors among each
other can be spared.
The invention makes it possible to determine the operating
properties of delivery pumps much more easily, flexibly and
robustly. In addition, the accuracy in determining the operating
properties of the delivery pump can be increased.
The discrete measuring points of the current consumption of the
motor are measured with a sufficiently high sampling frequency.
The operating voltage supply of the motor can have one or more
phases.
In a further development of the invention, it is provided that
the period is ascertained with the aid of an approximated
polynomial by the power values of the measuring points.
This enables precise determination of the operating properties
of the delivery pump in a simple manner.
In a further development of the invention, it is provided that
the period is ascertained with the aid of a polynomial which
takes into account statistical mean values of the power values
of the various measuring points over at least five, preferably
at least ten, particularly preferably at least fifty pump cycles
for interpolation points of the polynomial.
This enables precise determination of the operating properties
of the delivery pump in a simple manner.
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In a further development of the invention, it is provided that
a reference value is ascertained for the measuring points, at
which a maximum is present for the change of the particular
power value between two directly successive measuring points,
and the period is determined with the aid of the reference value.
This enables precise determination of the operating properties
of the delivery pump in a simple manner.
In a further development of the invention, it is provided that
the operating properties of the delivery pump are determined
with the aid of a load-displacement graph which is determined
from the torque curve ascertained in step d) using the period
determined in step b) and the reference phase angle determined
in step c).
This enables precise determination of the operating properties
of the delivery pump in a simple manner.
In a further development of the invention, it is provided that
the reference phase angle is determined with respect to the
absolute maximum of the power values of the measuring points
within a pump cycle.
This enables precise determination of the operating properties
of the delivery pump in a simple manner.
The object according to the invention is also solved by a pump
system of the aforementioned type, wherein furthermore a
measuring means is provided, which is designed to measure the
power consumption of the motor during its operation, and
furthermore a computing device with a memory is provided, which
is designed to carry out the method according to the invention
with the aid of the measuring means.
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A further object of the invention to describe a computer-
implemented method. The object of the invention directed to a
computer-implemented method is solved by the features of claim
8.
The invention is explained in more detail below with reference
to an exemplary embodiment shown in the accompanying drawings.
In the drawings:
figure 1 shows an exemplary embodiment of a system according
to the invention with a drill-rod borehole pump,
figure 2 shows an exemplary embodiment of a pump head of a
drill-rod borehole pump,
figure 3 shows an exemplary embodiment of a flowchart of the
method according to the invention,
figure 4 shows a first exemplary embodiment of a load-
displacement graph,
figure 5 shows load-displacement graphs for a pump at different
output levels,
figure 6 shows load-displacement graphs for a pump at different
loads and in different operating modes,
figure 7 shows a time representation of a current curve of an
electric drive motor for a drill-rod borehole pump.
Figure 1 shows an exemplary embodiment of a pump system 100
according to the invention with a drill-rod borehole pump 1 of
the sucker-rod pump type.
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The pump system 100 comprises a pump head 110 which is connected
to a kinematics converter 120 via a drill rod 5, 10.
The drill rods 5, 10 form a so-called "rod string" and run
through a borehole head 6, to which there is connected a flow
line 7 for discharging a pumped medium 14.
Adjacently to the borehole head 6 is a casing 8, in which there
runs a tube 9, guiding the drill rod 5 or 10.
Attached to the lower end of the drill rod 10 is the pump head
110, which includes a piston 11 in a barrel 12. A movement of
the piston 11 causes the pumped medium 14 to be pumped out.
The casing 8 is formed in a borehole 13.
For example, the kinematics converter 120 is driven by a prime
mover in the form of an electric motor 3 via a reduction gearing
4. The kinematics converter 120 may additionally comprise a
hydraulic power booster.
In this example, the mechanical connection of the kinematics
converter 120 is established via a running beam 2, but can vary
depending on the type of pump used.
A person skilled in the art is familiar with such kinematics
converters, as well as their description in the form of
"properties of a kinematics converter" by the transformation
function of mechanical movements and forces.
The kinematics converter 120 converts a rotary motion of the
motor 3 into a linear motion of the drill rod 5, 10.
The properties of the kinematics converter 120 can be described,
for example, in terms of leverage effects and transmission
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ratios, as well as in terms of electrical drive power and moving
masses. It should be noted that the position of a flywheel mass
along a rotational motion and the corresponding force applied
to the drill rod 10 are related in time, which is referred to
as a reference phase angle. For a particular pump arrangement,
a reference phase angle can be determined using the kinematics
principles of mechanics, as known to a person skilled in the
art.
Furthermore, a measuring means 110 is provided, which is
designed to measure the current consumption and the operating
voltage of the individual phases of the motor 3 during its
operation. This can be done, for example, by an ammeter or
voltmeter which measures discrete measuring points with current
or voltage values, in particular with high temporal resolution.
The measured current and operating voltage values can be used
to determine the effective power consumption and the apparent
power consumption.
Furthermore, a computing device 140 with a memory 150 is
provided, which is designed to carry out the method according
to the invention with the aid of the measuring means 130.
It is known to a person skilled in the art how a reference phase
angle for the kinematics converter 120 can be ascertained using
the properties of the kinematics converter 120 and the power
consumption 72 of the motor 3, which describes the relationship
between the maximum 83 of the power consumption 72 and the
maximum of the force acting on the drill rod of the borehole
pump 1.
It is also known to a person skilled in the art how a torque
curve can be determined from the power consumption 72 of the
motor 3 using the properties of the kinematics converter 120.
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Fig. 2 shows another, more detailed example of a prior art pump
head 111.
The rod string or drill rod 10 is driven as shown in Fig. 1 and
is set into an up-and-down linear motion.
In the variant of the pump head 111 shown, there is arranged in
the borehole 13 a cover tube 15 with vertical grooves, which
guides inside the cover tube 15, via a holding device 16 and a
self-aligning bearing 17, a rotating tube 18 with spiral
grooves.
A receiving tube 19 is connected via a wing nut 20 to a piston
assembly 21, which is located in a pump liner 22.
A calibrated rod 23 is connected to the drill rod 10 via a pin
24 and a holding device 25, which drives the piston assembly by
way of the linear motion.
Fig. 3 shows an exemplary embodiment for a flowchart of the
method according to the invention with the following steps:
a) measuring the current consumption and the operating
voltage of the motor 3 in the form of discrete measuring
points with a sampling frequency over at least one pump
cycle with which four operating phases of the borehole
pump 1 can be associated in each case, and determining
therefrom the power consumption 72 of the motor 3 with
power values,
b) determining, for one pump cycle, a period 85 and a
maximum 82 of the power consumption 72 that corresponds
to the torque maximum of the borehole pump 1,
c) determining a reference phase angle for the kinematics
converter 120 with the aid of the properties of the
kinematics converter 120 and the power consumption of
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the motor 3, which reference phase angle describes the
relationship between the maximum 82 of the power
consumption and the maximum of the force acting on the
drill rod of the borehole pump 1,
d) ascertaining a torque curve from the power consumption
of the motor 3 with the aid of the properties of the
kinematics converter 120,
e) determining the operating properties of the delivery
pump 1 from the torque curve ascertained in step d)
using the period determined in step b) and the reference
phase angle determined in step c).
The power values can be determined by the product of the discrete
current values and the operating voltage.
The period 85 can be ascertained, for example, using an
approximated polynomial 80 by the power values of the measuring
points.
However, the period 85 can also be determined, for example, with
the aid of a polynomial 80 which takes into account statistical
mean values of the power values of the various measuring points
over at least five, preferably at least ten, particularly
preferably at least fifty pump cycles for interpolation points
of the polynomial.
A reference value 81 can be determined for the measuring points,
at which reference value a maximum is present for the change of
the particular power value between two directly successive
measuring points, and the period 85 is ascertained with the aid
of the reference value 81.
The operating properties of the delivery pump 1 can be determined
with the aid of a load-displacement graph 30, 50, 54, 57, 60-
65, which is determined from the torque curve ascertained in
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step d) using the period determined in step b) and the reference
phase angle determined in step c).
The reference phase angle can be determined with respect to the
absolute maximum of the power values of the measuring points
within a pump cycle.
Figure 4 to figure 6 show examples of load-displacement graphs
which are often used to determine the operating properties of
drill-rod borehole pumps.
Fig. 4 shows a load-displacement graph 30.
The position 31 of the polished bar is plotted on the x-axis,
and the load 32 of the polished bar is plotted on the y-axis.
The lowest point of the pump stroke 33 and the highest point of
the pump stroke 34 can be seen.
Furthermore, a tip of the polished rod 35 (PPRI) is shown.
A map 36 of the polished rod for a pump speed equal to zero is
shown by dashed lines.
Further, a map 37 of the polished rod for a pumping speed greater
than zero is shown.
A minimum load of the polished rod 38 (MPRL) is shown.
A gross piston load 39 can also be read.
In addition, a weight of the rods in the fluid 40 can be
determined, as well as forces 41 and 42, and a pump stroke or
pump displacement 43.
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In Fig. 5, load-displacement graphs 50 are shown with bar load
at setpoint as a function of load 32 of the polished bar across
the particular position 31 of the polished bar.
A load-displacement graph 51 shows operation at full pump
capacity.
A load-displacement graph 52 shows operation when the pumped
medium is empty.
A corresponding setpoint 53 can be recognized.
Further, load-displacement graphs 54 are shown with bar load at
a change of operation as a function of the load 32 of the
polished bar across the particular position 31 of the polished
bar, wherein respective angles 55, 56 can be read.
Further, load-displacement graphs 57 are shown with bar load
with the particular mechanical work of the bars.
Fig. 6 shows load-displacement graphs 60-65 for various
operating conditions.
Graph 60 shows load-displacement graphs during normal operation.
Graph 61 shows load-displacement graphs for a fluid bearing.
Graph 62 shows load-displacement graphs under gas action in the
underground store.
Graph 63 shows a load-displacement graph in the event that a
piston is stuck.
Graph 64 shows a load-displacement graph in the event of leakage
through a stationary valve.
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Graph 65 shows a load-displacement graph in the event of leakage
through a moving valve.
Fig. 7 shows an example of a time display of a power curve of
an electric drive motor for a drill-rod borehole pump, which was
ascertained from the current consumption and operating voltage
of the motor 3.
The display has a time axis 70 and an axis 71 for amplitude of
current or power consumption.
A power consumption 72 is shown for which a zero point or zero
axis 80, and a polynomial for averaged power consumption 81 can
be determined.
For the polynomial 80, a maximum value of the averaged power
consumption 82, as well as zero crossings of the averaged power
consumption 83, 84 can be ascertained.
Furthermore, a period 85 of the averaged power consumption can
be determined for the polynomial 80.
From this, a phase angle 86 of the averaged power consumption
can be ascertained, which describes the relationship between the
rotary motion of the motor 3 and the drill rod 10 of the pump
1.
From the ascertained values, a corresponding load-displacement
graph can be ascertained in order to easily derive the operating
properties of the drill-rod borehole pump 1.
List of reference signs:
1 drill-rod borehole pump
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2 running beam
3 prime mover, motor
4 reduction gearing
polished rod
6 borehole head
7 flow line
8 casing
9 tube
rod string
11 piston
12 barrel
13 borehole
14 pumped medium
cover tube with vertical grooves
16, 25 holding device
17 self-aligning bearing
18 rotating rube with spiral grooves
19 receiving tube
wing nut
21 piston assembly
22 pump liner
23 calibrated rod
24 pin
load-displacement graph
31 position of the polished rod
32 load of the polished rod
33 lowest point of the pump stroke
34 highest point of the pump stroke
tip of the polished rod, PPRI
36 map of the polished rod for pump speed equal to zero
37 map of the polished rod for pump speed greater than
zero
38 minimum load of the polished rod, MPRL
39 gross piston load
weight of the rods in the fluid
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41, 42 force
43 displacement
50 load-displacement graph with bar load at setpoint
51 pump, full power
52 pumped empty
53 setpoint
54 load-displacement graph with rod load with change of
operation
55, 56 angle
57 load-displacement graph with mechanical work of the
rods
60 load-displacement graph in normal operation
61 load-displacement graph with a fluid bearing
62 load-displacement graph under gas action
63 load-displacement graph in the event that a piston is
stuck
64 load-displacement graph in the event of leakage
through a stationary valve
65 load-displacement graph in the event of leakage
through a moving valve
70 time axis
71 axis for amplitude of current or power consumption
72 power consumption
80 selected zero point or zero axis
81 polynomial for averaged power consumption
82 maximum value of the averaged power consumption
83, 84 zero crossing of the averaged power consumption
85 period of the averaged power consumption
86 ascertained phase angle of the averaged power
consumption
100 pump system
110, 111 pump head
120 kinematics converter
130 measuring means
140 computing device
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150 memory
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