GB2334284A - Submersible downhole pumping system - Google Patents
Submersible downhole pumping system Download PDFInfo
- Publication number
- GB2334284A GB2334284A GB9911625A GB9911625A GB2334284A GB 2334284 A GB2334284 A GB 2334284A GB 9911625 A GB9911625 A GB 9911625A GB 9911625 A GB9911625 A GB 9911625A GB 2334284 A GB2334284 A GB 2334284A
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- GB
- United Kingdom
- Prior art keywords
- motor
- speed
- vmin
- choke
- pump
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000005086 pumping Methods 0.000 title claims description 12
- 238000004519 manufacturing process Methods 0.000 claims abstract description 57
- 238000013022 venting Methods 0.000 claims abstract description 34
- 238000011144 upstream manufacturing Methods 0.000 claims description 34
- 238000000034 method Methods 0.000 claims description 23
- 239000002689 soil Substances 0.000 claims description 12
- 229930195733 hydrocarbon Natural products 0.000 abstract description 21
- 150000002430 hydrocarbons Chemical class 0.000 abstract description 21
- 239000004215 Carbon black (E152) Substances 0.000 abstract 1
- 230000006870 function Effects 0.000 description 21
- 238000010438 heat treatment Methods 0.000 description 5
- 230000001276 controlling effect Effects 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000006866 deterioration Effects 0.000 description 3
- 239000003129 oil well Substances 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 230000001052 transient effect Effects 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000011143 downstream manufacturing Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000011017 operating method Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/12—Methods or apparatus for controlling the flow of the obtained fluid to or in wells
- E21B43/121—Lifting well fluids
- E21B43/128—Adaptation of pump systems with down-hole electric drives
Abstract
A hydrocarbon production well comprising a submerged pump 5 driven by an electric motor 6, an oil outlet choke 17 and a gas venting choke 22 is operated by acting, during various production phases, on the said chokes and on the speed of the electric motor 6 either in turn or simultaneously. Furthermore, correct operation of the well is constantly checked. The current drawn by the motor 6 is also checked so that it does not cross thresholds that vary as a function of the speed of the motor 6.
Description
TECHNICAL FIELD
The present invention relates to a method of operating an oil- and gas-producing oil well activated by a submersible downhole pumping system.
STATE OF THE PRIOR ART
In the case of certain oil wells, the rate at which hydrocarbons are produced in the form of oil and gas is low because of the low pressure in the reservoir.
In order to increase the production of hydrocarbons, use is conventionally made of a method known by the name of an electrical submersible pumping method.
According to this method, a pumping system comprising a pump driven by an electric motor is placed in the wellbottom, so as to suck oil in from the hydrocarbons reservoir and deliver it into a production column which connects the wellbottom at reservoir level with the well head at the top.
The electrical power supply for the motor is usually provided by a frequency converter which allows the rotational speed of the pump to be varied.
The production column defines, with the casing that forms the wall of the well, an annular space which allows the venting of the excess free gas under the wellbottom thermodynamic conditions.
At the top of the well, the production column is connected to a pipe equipped with an oil outlet choke, and the annular space is extended by another pipe equipped with a gas venting choke. These two chokes allow the oil outlet flow rate and gas venting flow rate respectively to be regulated.
One method of operating such a well, described in Patent US 5,634,522, consists in slaving the measured level to which the oil rises in the annular space to a predetermined reference value by acting on the extent to which the oil outlet choke is open.
It is also known practice for the motor speed to be increased linearly as a function of time during the initial start-of-production phase and during a restart after a stoppage.
The electric motor is conventionally protected against excessive heatIng by a crcui.t breaker which cuts off the electric power supply when the current draw exceeds a very high fixed threshold value.
This protection has the drawback of not being effective under all well operating conditions. For example, when the flow rate of the oil produced Is low, as the current drawn by the motor is low, the Jouleeffect heating is small, but the amount of cooling provided by the oil which flows through the motor is also low. Under such conditions, the combination of these two opposite effects may result in an excessive temperature rise in the motor without the protective device being able to come into action because the very high drawn-current threshold has not been exceeded.
Such rises in temperature lead, over time, to degradation of the motor and eventually lead to damage thereto.
Other thermodynamic, thermal and hydraulic phenomena may temporarily lead to an excess of free gas in the pump. This excess of gas may, in certain cases, lead to instabilities or to insufficient cooling. These phenomena, which have an influence on the life of the motor and of the pump are not taken into account in the known operating methods.
Another drawback of these known methods is that any anomaly in operation leads to production being stopped and to costly restarts.
SUMMARY OF THE INVENTION
The precise purpose of the present invention is to overcome these drawbacks by proposing a method of operating an oil well activated by an electric submersible pump pumping system, which improves the protection of the pump and of its electric drive motor under all operating conditions, which reduces thf effects of thermal and hydraulic shock, and which ensures consistency between the settings of the power supply to the electric motor and the settings of thf well outlets in order to minimize production stoppages.
By virtue of the invention, the life of thE pumping system is increased and the number of costlh repair interventions and associated costly restarts ic greatly reduced.
To this end, the invention proposes a method oi operating an oil and gas production well activated by c pumping system, comprising, placed at the wellbottom, submerged pump driven by an electric motor which drawl a known amount of current, the said well comprising, at its top, an oil outlet choke and a gas venting choke, characterized in that it comprises a starting phasE which consists in running the following steps: - a preparative step which consists in:
acting on the gas venting choke to bring tht pressure upstream of the said choke to < predetermined starting value,
acting on the oil outlet choke to bring thf pressure upstream of the said choke to
predetermined starting value, re-closing the oil outlet choke,
checking that, with no power applied to thf electric motor, the condition of the pump i compatible with starting, - a start-of-production- step which consists in:
gradually applying power to the motor until thf pump is running at a predetermined minimum speed,
checking, after a time, that the pressure upstrear of the oil outlet choke has exceeded a pre
determined pressure-rise threshold,
checking, after a time, that the current drawn b the electric motor has exceeded a predetermine
threshold,
leaving the pump running if these two thresholds
have been exceeded, otherwise stopping the pump,
gradually increasing the extent to which the oil
outlet choke is open, up to a predetermined value, waiting for a predetermIned stabilizing time, checking for correct operation by simultaneously makIng checks on the current drawn by the motor
and on the production of the well using at least
one production indicator,
regulating the pressure upstream of the gas
venting choke to the predetermined starting value.
According to another feature of the invent ion, the compatIbIlity of the condition of the pump with starting comprises the following checks: - that the pump, rotating and equipped with a
direction-of-rotation sensor is not running In the
opposite direction to its normal direction of
rotation, - that the time between two successive attempts at
starting exceeds a predetermined value, - that after a predetermined number of attempts at
starting in a predetermined time, the next attempt
does not occur until a predetermined time has
elapsed.
According to another feature of the invention, with the current drawn by the motor being compared with very high and very low thresholds independent of the speed of the motor, a crossing of one of the said thresholds causing the pump to be stopped, the checks on the current drawn by the electric motor for checking correct operation, additionally consist in: - comparing the value of the said current with a low
threshold and, if the threshold has been crossed and
if the time for which it is crossed exceeds a
predetermined value, stopping the pump, - after a predetermined time, checking the stability of
the said current and if an instability is detected
and if the duration of the instability exceeds a
predetermined value, stopping the pump.
According to another feature of the invention, the checks on the production of the well consist in taking as a production indicator at least one physical variable that indicates the oil outlet flow and in comparing the value of the said variable with a predetermined threshold, the threshold being considered as actually having been exceeded when it is so continuously for a predetermined duration, and if the threshold has been exceeded, in stopping the pump.
According to another feature, after the starting phase, under production conditions, the invention consists in simultaneously performing the following operations: - increasing the speed of the motor up to a
predetermined target value, - opening the oil choke up to a value that is
calculated as a function of the target value of the
speed of the motor, - acting on the gas venting choke so as to keep the
pressure upstream of the said choke at a value that
is calculated as a function of the target value of
the speed of the motor, - then checking for correct operation by performing
checks on the current drawn by the motor and on the
well production, using production indicators.
According to another feature of the invention, the extent to which the oil outlet choke is open is calculated by applying the following formula:
Soil = a(V - Vmin) + Smin if Vmin < V < Vmax in which:
Soil represents the extent to which the oil outlet choke is open
V represents the target value of the speed of the electric motor a is a constant
Smin is a constant which represents the minimum extent to which the oil outlet choke is open
Vmin and Vmax respectively represent the minimum and maximum speeds of the motor, a, Smin, min and Vmax are determined from characterIstIcs of the well, of the pump and of the motor.
According to another feature cf the invent Ion, the pressure upstream of the gas venting choke is calculated by applyIng the following formula:
Pgas = ss(v - Jmin) + Po if Vmin < V < Vmax in which
Pgas represents the pressure upstream of the gas venting choke,
V represents the target value of tre speed of the electric motcr ss is a constant Po is a constant
Vmin and Vmax respectively represent the minimum and maximum speeds of the motor, Po, Vmln and Vmax are determined from characteristics of the well, of the pump and of the motor.
According to another feature of the invention, under production conditions, with the current drawn by the motor being compared with very high and very low thresholds independent of the speed of the motor, a crossing of one of the said thresholds causing the pump to be stopped, the checks on the current drawn by the electric motor for checking correct operation, additionally consist in: - comparing the value of the said current with high and
low thresholds which vary as a function of the speed
of the motor, - if a threshold is crossed, reducing the speed, and if
the threshold is still crossed, stopping the pump, - checking the stability of the said current, and if an
instability is detected7 reducing the speed to a
predetermined value, and if the duration of the
instability exceeds a predetermined value, stopping
the pump.
According to another feature of the invent ion, under production conditions, the high and low thresholds that vary as a function of the speed arf calculated by applying the following formulae:
Ihigh = INmin + y(V - Vmin) + Al if Vmin < V < Vmax
Ilow = INmin + y(V - Vmin) - Al if Vmin < V < Vmax
in which:
Ihigh represents the high threshold for the current
drawn by the motor,
Ilow represents the low threshold for the current drawn by the motor,
V represents the speed of the electric motor,
INmin is a constant which represents the minima nominal value of the current drawn by the motor,
Vmin and Vmax respectively represent the minimum anc maximum values of the speed of the motor determinec from characteristics of the well, of the pump and oi the motor,
y and Al are constants calculated for each well from
characteristics of the motor.
According to another feature of the invention the checks on the production of the well consist Ir taking as a production indicator at least one physics variable that indicates the oil outlet flow and ir comparing the value of the said variable with at least one predetermined threshold, the threshold bein considered as actually having been exceeded when it is so continuously for a predetermined duration, and ii the threshold has been exceeded, in reducing the speed.
According to another feature of the invention the physical variable that indicates the oil outlet flow is chosen from the group consisting of a pressure difference created by a restriction on the oil outlet, the vent gas flow, the wellbottom pressure upstream oi the pump, the pressure upstream of the oil outlet choke and the oil outlet temperature.
According to another feature, with the wel; being equipped with a safety device, the invention consists in closing the oil outlet and gas Invention chokes and in stopping the motor immediately when th safety device comes into action, to strengthen its own actions.
Another subject of the invention is a method of operating an oil and gas production well activated by a pumpIng system, comprising, placed at the wellbottom, a submerged pump driven by an electric motor which draws a known amount of current, the said well comprising, at its top, an oil outlet choke and a gas venting choke, characterized in that after a starting phase it consists in sImultaneously performing the following operations: - increasing the speed of the motor up to a
predetermined target value, - opening the oil-outlet choke up to a value that is
calculated as a function of the target value of the
speed of the motor, - acting on the gas venting choke so as to keep the
pressure upstream of the said choke at a value that
is calculated as a function of the target value of
the speed of the motor, - then checking for correct operation by performing
checks on the current drawn by the motor and on the
well production, using production indicators.
According to another feature of the invent ion, under production conditions, the extent to which the oil outlet choke is open is calculated by applying the following formula:
Soil = a(V - Vmin) + Smin if Vmin < V < Vmax in which:
Soil represents the extent to which the oil outlet choke is open
V represents the target value of the speed of the electric motor a is a constant
Smin is a constant which represents the minimum extent to which the oil outlet choke is open
Vmin and Vmax respectively represent the minimum and maximum speeds of the motor, a, Smin, Vmin and Vmax are determined from characteristics of the well, of the pump and of the motor.
According to another feature of the Invention, the pressure upstream of the gas venting choke is calculated by applying the following formula: Pgas = P(V - Vmin) + Po if Vmin c V < V ( Vmax in which:
Pgas represents the pressure upstream of the gas venting choke,
V represents the target value of the speed of the electric motor, ss is a constant
Po is a constant
Vmin and Vmax respectively represent the minimum and maximum speeds of the motor, Po, Vmin and Vmax are determined from characteristics of the well, of the pump and of the motor.
According to another feature of the invent ion, with the current drawn by the motor being compared with very high and very low thresholds independent of the speed of the motor, a crossing of one of the said thresholds the pump being stopped, the checks on the current drawn by the electric motor for checking correct operation, additionally consist in: - comparing the value of the said current with high and
low thresholds calculated as a function of the speed
of the motor, - if a threshold is crossed, reducing the speed and if
the threshold is still crossed, stopping the pump, - checking the stability of the said current, and if an
instability is detected, reducing the speed to a
predetermined value, and if the duration of the
instability exceeds a predetermined value, stopping
the pump.
According to another feature of the invention, the high and low thresholds are calculated by applying the following formulae:
Ihigh = INmin + y(V - Vmin) + Al if Vmin < V < Vmax
Ilow = INmin + y(V - Vmin) - Al if Vmin < V < Vmax
in which:
Ihigh represents the high threshold for the current
drawn by the motor,
Ilow represents the low threshold for the current
drawn by the motor,
V represents the speed of the electric motor, INmln is a constant which represents the minimum
nominal value of the current drawn by the motor,
Vmin and Vmax respectively represent the minimum and
maximum values of the speed of the motor determined
from characteristics of the well, of the pump and of
the motor,
y and Al are constants calculated for each well from
characteristics of the motor.
According to another feature of the invent ion, the checks on the production of the well consist in taking as a production indicator at least one physical variable that indicates the oil outlet flow and in comparing the value of the said variable with at least one predetermined threshold, the threshold being considered as actually having been exceeded when it is so continuously for a predetermined duration, and if the threshold has been exceeded, in reducing the speed.
According to another feature of the invention, the physical variable that indicates the oil outlet flow is chosen from the group consisting of a pressure difference created by a restriction on the oil outlet, the vent gas flow, the wellbottom pressure upstream of the pump, the pressure upstream of the oil outlet choke and the oil outlet temperature.
According to another feature, with the well being equipped with a safety device, the invention consists in closing the oil outlet and gas venting chokes and in stopping the motor immediately when the safety device comes into action, to strengthen its own actions.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 diagrammatically depicts a well for producing hydrocarbons in the form of oil and gas, activated by a submersible pumping system.
Figure 2 represents the value of the high and low thresholds for the current drawn by the motor as a function of its speed.
Figure 3 represents the extent to which the oil outlet choke is open as a function of the motor speed.
Figure 4 represents the pressure upstream of the gas venting choke as a function of the motor speed.
Figure 5 is a timing diagram for attempts at starting the motor.
DETAILED DESCRIPTION OF THE INVENTION
In general, the method of the invention is used for operating a hydrocarbons production well activated by a pumping system.
Figure 1 represents a hydrocarbons production well which comprises:
- a tubular production column 1 which connects the wellbottom 31 which is at the level of the hydrocarbons reservoir 30, to the well head situated at the top,
- a tube 2 concentric with the column 1 which lines the wall of the well and at its bottom has a number of openings 4 through which the hydrocarbons pass from the reservoir into the wellbottom 31,
- an annular space 3 determined by the column 1 and the tube 2 and via which the excess free gas under the wellbottom thermodynamic conditions is vented,
- a pump 5 submerged in the hydrocarbons contained in the wellbottom 31, the outlet of which pump is connected to the bottom end of the production column 1 intended to raise the hydrocarbons,
- an electric motor 6 mechanically connected to the pump 5 and equipped with supply terminals 13,
- a frequency converter 10 with output terminals 1', powered by means of a cable 12 from an electrical network which is not depicted in Figure 1,
- a power supply cable 7 for the electric motor 6 which connects the output terminals 11 of the frequency converter 10 to the power supply terminals 13 of the motor 6,
- a reverse-rotation sensor 8, placed on the cable 7, which on one output delivers an electrical signal when the pump 5 is running in the opposite direction to its normal direction of rotation,
- a current sensor 9 which, on one output, delivers an electrical signal representing the current drawn by the motor 6,
- an oil outlet pipe 14 connected to the top of the production column 1, via which the oil produced is conveyed towards a downstream processing unit not depicted in Figure 1,
- an oil outlet choke 17 mounted on the pipe 14 and intended to regulate the flow of oil produced,
- an actuator 18 mechanically connected to the choke 17 and which has a control input,
- a pressure sensor 15 sensing the pressure upstream of the choke 17 and which on one output delivers an electrical signal proportional to the said pressure,
- a sensor 16 indicating the oil flow in the pipe 14, comprising an orifice plate inserted in the pipe 14 and a sensor that measures the differential pressure created across the said plate,
- a gas-venting pipe 19 connected to the top of the annular space 3 via which the excess gas produced is discharged,
- a gas venting choke 22 mounted on the pipe 19 and intended to regulate the flow of gas discharged by the pipe 19,
- an actuator 23 mechanically connected to the choke 22 and which has a control input,
- a pressure sensor 20 for sensing the pressure upstream of the choke 22,
- a sensor 21 for measuring the vent gas flow,
- a programmable controller 24 which has a number of inputs 25a, 25b, 25c, 25d, 25e, 25f and 25g, connected respectively to the output 28 of the frequency converter 10 and to the sensors 9, 8, 21, 20, 16, 15 and a number of outputs 26a, 26b and 26c connected respectively to the input 27 of the frequency converter 10 and to the control inputs of the actuators i8 and 23,
- operator/controller 24 dialogue means 29.
The controller 24 additionally comprises, and this is not depicted in Figure 1, a memory pre-loaded with a program and with data needed for operating the well, particularly all the predetermined values of the regulation variables. This information being entered beforehand by an operator using the controller/operator dialogue means 29 and being modifiable during production using the same means 29.
The frequency converter 10, powered from the electrical network of a set frequency, delivers on its power output 11, an electrical voltage at a variable frequency that can be altered by a signal applied to its input 27. It also comprises a switch-circuit breaker which allows the motor 6 to be switched on and off, this being controllable by applying an electrical signal to its input 27, the said signal being emitted by the output 26a of the controller.
The frequency converter 10 delivers, on its output 28, a signal that represents the frequency of the voltage applied to the electric motor 6. This signal applied to the input 25a of the controller allows the latter to calculate the speed of the motor 6.
As the speed of the electric motor 6 is proportional to the frequency of its supply voltage, this speed can be controlled from the controller 24 by a signal delivered by the output 26a connected to the input 27 of the converter 10.
The hydrocarbons production well also comprises, and this is not depicted in Figure 1, a safing device connected by an output to one input of the controller 24. The safety device comprises shut-off valves mounted on the production column 1 and on the annular space 3 and controllable by electronic modules which perform logic functions of safing the well.
The method of the invention consists, during a phase of starting the well, that is to say of starting initial production or restarting after a stoppage during production, in running the following steps: - a preparative step during which the controller 24: determines, using a control algorithm, on the
basis of the signal delivered by the sensor 20
that senses the pressure upstream of the gas
venting choke 22, a control value for the actuator
23 so as to bring this pressure to a predetermined
starting value, determines, by means of a control algorithm, on
the basis of the signal delivered by the sensor 15
that senses the pressure upstream of the oil
outlet choke 17, a value for controlling the
actuator 18 for bringing this pressure to a
predetermined starting value,
then delivers on its output 26b a signal for
controlling the actuator 18 to close the oil
outlet choke 17,
next checks that, with no power applied to the
electric motor 6, the condition of the pump 5 is
compatible with starting, without the risk of
mechanical deterioration, that is to say that the
pump 5 is stopped or is running in its normal
direction of rotation which will allow the
hydrocarbons sucked in from the wellbottom to be
delivered upwards. If it is not, if the pump 5 is
running in the opposite direction to its normal
direction of rotation under the effect of the
natural circulation of hydrocarbons, the signal
delivered by the sensor 8 is interpreted by the
controller as a prohibition from starting the
motor 6, checks that the time between two successive
attempts at starting is greater than a
predetermined value T1, so as to prevent excessive
heating. For that, after each starting, the
controller triggers a time counter whose content
it compares, on the next start, with the value T1 predetermined on the basis of the recommendations
of the manufacturer of the motor 6 and the
conditions in which it is operating; this value is
stored in memory in the form of a data item,
checks that after a number n = 3 of attempts at
starting in a time T2 that the uni1, that is to say
the fourth attempt does not occur until the motor
has had a time T3 to cool. T1, T2 and T3 are
predetermined from the characteristics of the
motor and are represented on the timing diagram of
Figure 5.
A start-of-production step during which the controller 24: delivers on the output 26a a signal for gradually
applying power to the motor 6 until the pump 5 is
running at a predetermined starting speed,
checks after a time that the pressure upstream of
the oil outlet choke, measured using the pressure
sensor 15, exceeds a predetermined pressure-rise
threshold,
checks, after a time, that the current drawn by
the motor 6 and measured by the sensor 9 exceeds a
predetermined threshold,
allows the pump 5 to continue to run if these two
thresholds are exceeded, and otherwise stops the
pump 5, giving the frequency converter i0 an order
to stop, gradually increases the extent to which the oil
outlet choke 17 is open, up to a predetermined
value,
waits for a predetermined stabilizing time, checks correct operation of the well by
simultaneously performing checks on the current
drawn by the motor 6 and on the production of the
well using a production indicator,
regulates the pressure upstream of the gas venting
choke 22 to the predetermined starting value by
action on the said choke.
In addition to the checks usually performed, which consist in comparing the current drawn by the motor 6 with very high and very low threshold values independent of the motor speed, a crossing of one of the said thresholds causing the pump to be stopped, the controller 24 compares the said current with a low threshold.
If the threshold is crossed, the controller stops the pump 5 by giving appropriate orders to the frequency converter 10.
The controller also checks the stability of the current drawn by the motor 6, in order to detect instabilities. This check consists in making sure that the current drawn by the motor 6 does not exceed high and low limits a given number of times in a given time.
These various parameters are determined by taking account of the characteristics of the motor 6 and of the pump 5.
If an instability is detected, the controller stops the pump 5, by giving appropriate orders to the speed variator 10.
To perform checks on the production of the well, the controller 24 compares the oil outlet flow measured by the sensor 16 connected to the input 25f of the controller, with an experimentally determined threshold value. A threshold is considered to have actually been exceeded when it is exceeded continuously for a minimum length of time, so that transient crossings which do not signify anomalies are not taken into account. If a threshold is exceeded then the controller gives the frequency converter an order to stop the pump 5.
Thus, by virtue of the invention, during a phase of restarting the well, the oil outlet choke (17) does not remaln closed, as this would lead to excessive heating of and damage to the motor.
After the phase of starting the well, according to the invention, the controller 24 performs the following operations simultaneously: - delivers on its output 26a a signal to increase the
frequency of the converter 10, so as to increase
the speed of the motor 6 up to a target speed value
predetermined to ensure the desired oil production
flow. This flow may be fixed in the form of a value
entered into the controller 24 or altered as a
function of the operating conditions of the unit
for treating the hydrocarbons produced which is
placed downstream of the well, - delivers on its output 26b a signal for controlling
the actuator 18 to open the oil outlet choke 17 up
to an amount that is a function of the target speed
value, calculated by applying the following
formula:
Soil = a(V - Vmin) + Smin if Vmin < V < Vmax
in which:
Soil represents the extent to which the oil choke
is open
V represents the target value of the speed of the
electric motor 6
a is a constant
Smin is a constant which represents the minimum
extent to which the oil choke is open
Vmin and Vmax respectively represent minimum and
maximum speeds of the motor,
a, Smin, Vmin and Vmax are determined from the
characteristics of the well, of the pump and of the
motor.
Figure 3 represents, in the form of the curve 44,
the value Soil which is the extent to which the oil
outlet choke 17 is open, as a function of the
target value of the speed V of the motor 6.
- delivers on its output 26c a signal for controlling
the actuator 23 for keeping the pressure upstream
of the gas venting choke 22 at a value that is a
function of the target speed value, calculated by
applying the following formula:
Pgas = 5(V - Vmin) + Po if Vmin < V < Vmax
in which
Pgas represents the pressure upstream of the gas
venting choke 22 and measured by the sensor 20,
V represents the target value of the speed of the
electric motor 6 ss is a negative constant
Po is a constant
Vmin and Vmax respectively represent the minimum
and maximum speeds of the motor, , Po, Vmin and Vmax are determined from the
characteristics of the well, of the pump and of the
motor.
Figure 4 depicts, in the form of the curve 45, the
value Pgas of the pressure upstream of the gas
venting choke 22 as a function of the target value
of the speed V of the motor 6.
- checks correct operation of the well by
simultaneously performing checks on the current
drawn by the motor 6 and on the production of the
well using a production indicator.
To perform checks on the current drawn by the electric motor 6, the controller compares the value of the said current with high and low thresholds that are a function of the speed of the motor 6. These thresholds are calculated by applying the following formulae:
Ihigh = INmin + y(V - Vmin) + Al if Vmin < V < max
Ilow = INmin + y(V - Vmin) - Al if Vmin < V < max in which:
Ihigh represents the high threshold for current drawn by the motor 6,
Ilow represents the low threshold for current drawn by the motor 6,
V represents the speed of the electric motor 6 known by the controller from the value of the frequency of the converter 10,
INmin is a constant which represents the minimum nominal value of the current drawn by the motor 6,
Vmin and Vmax respectively represent the minimum and maximum values of the speed of the motor determined from characteristics of the well, of the pump 5 and of the motor 6, y and Al are constants calculated for each well, which take account of the characteristics of the motor 6 and of its actual cooling by the pumped hydrocarbons.
Figure 2 represents in the form of curves 40 and 41 respectively, the values Ihigh and Ilow of the high and low thresholds of the current drawn by the motor 6 as a function of the speed V of the motor. The intervals 42 and 43 in the variation of I represent Al and -AI respectively.
If a threshold is crossed, the controller reduces the speed of the motor 6 to a predetermined value, and if the threshold is still crossed after a predetermined period of time, it stops the pump 5 by giving an order to the frequency converter 10.
The controller also checks the stability of the current drawn by the motor 6 during the phase following starting, so as to detect instabilities which characterize swift variations in the conditions of flow of the hydrocarbons due, for example, to the presence of an excessive amount of gas at the pump, and which may in particular lead to deterioration of the motor 6 and of the pump 5. This check consists in making sure that the current drawn by the motor 6 does not exceed a high limit a given number of times in a given time.
These various parameters are determined by taking account of the characteristics of the motor 6 and of the pump 5.
If an instability is detected, the controller reduces the speed of the motor 6 to a predetermined value, and if the instability is still present, stops the pump 5, by giving suitable orders to the frequency converter 10.
To carry out checks on the production of the well, the controller 24 compares the oil outlet flow measured by the sensor 16 connected to the input 25f of the controller, with predetermined high and low threshold values. A crossing of a threshold is considered to have actually occurred when it is continuous for a minimum length of time, so that transient crossings which do not signify anomalies are not taken into account. If a threshold is exceeded then the controller reduces the motor speed and gives the frequency converter an order to stop the pump 5 if the fault persists.
The method of the invention also consists in coordinating the operating actions with the well safing actions. When the safing device triggers a series of safing actions it simultaneously delivers a signal on an output connected to an input of the controller 24.
The latter interprets this signal and issues the orders to close the oil outlet and gas venting chokes, to stop the motor 6, which have the effect of reinforcing the safing actions.
Another advantage of the invention is that it protects the pump against excessively wide or excessively prolonged opening of the oil outlet choke, which might be unsuitable for the characteristics of the pump. It also allows the pump to run in the presence of free gas because, by its actions of active monitoring, it guarantees that the well operating conditions are acceptable.
By virtue of the method of the invention, the motor is protected against deterioration by heating under all running conditions, particularly at low speed during the starting phases and during the start-ofproduction phases while at the same time allowing maximum production of hydrocarbons.
The invention also makes it possible to protect the well equipment, particularly the motor and the pump, from mechanical and hydraulic shocks thanks to the simultaneous actions on the oil outlet and gas venting chokes and on the motor speed.
EXAMPLE
The values of parameters used for implementing the method of the invention for operating a hydrocarbons production well from a reservoir lying at a depth of 650 metres, the static wellbottom pressure of which was 50 bar will be found below by way of example.
This well, equipped with a tubular production column 114 mm in diameter surrounded by a concentric tube 244 mm in diameter was activated by a pumping system, comprising, placed in the wellbottom, a submerged 36stage pump driven by a 200 kW electric motor.
The electrical power supply for the motor was provided by a 360kVA frequency converter allowing an operating range of 1600 to 2700 m3/day of hydrocarbons pumped, the frequency of the current delivered being between 47 and 61 Hz, which corresponds to a minimum speed of 2740 rpm and a maximum speed of 3560 rpm.
The nominal current drawn by the motor was 77 A at 50 Hz under a voltage of 2000 V.
The target speed was equal to the maximum motor speed.
After a restart following a production stoppage, during the step in preparation for the starting phase, the pressure upstream of the gas venting choke was brought to 20 bar and the pressure upstream of the oil outlet choke was brought to 17 bar.
The minimum time to be waited between two successive attempts at starting was 20 min.
The minimum time to be waited after three attempts at starting in a period of 120 min was 60 min.
During the start-of-production step, the minimum speed reached by the motor after the gradual application of power thereto corresponded to a supply frequency of 47 Hz, namely to 2740 rpm.
The threshold for the rise in pressure upstream of the oil outlet choke was 20 bar and the threshold above which the current drawn by the motor had to lie was 36 A.
The extent to which the oil outlet choke was open, achieved after it had been gradually increased, was 70%.
The low threshold with which the current drawn by the motor was compared, to perform the check on the said current in order to check correct operation, was 36 A.
The stability of the current drawn by the motor was checked by making sure that the value of the said current did not exceed, more than five times in one minute, its mean value calculated over a period of time of 60 seconds, increased by 3 A.
As the production indicator chosen for checking correct operation was a pressure difference across an orifice, converted into an oil flow rate, the threshold with which it was compared was 1000 m3/day.
The pressure upstream of the gas venting choke was regulated to the predetermined starting value, namely 20 bar.
After the starting phase, the motor speed was increased to a target value which was obtained by setting the frequency of the supply current to 61 Hz, namely 3560 rpm.
At the same time, the oil outlet choke was opened up to a value that was calculated as a function of the speed, using the following formula:
Soil = a(V - Vmin) + Smin if Vmin < V < Vmax
in which:
Soil represents the extent to which the oil outlet
choke is open
V represents the target value of the speed of the
electric motor
a is a constant equal to 0.036
Smin is a constant equal to 70 which represents the
minimum extent to which the oil outlet choke is open
Vmin = 2740 rpm and Vmax = 3560 rpm, respectively
represent the minimum and maximum speeds of the
motor,
A value Soil = 100% was thus obtained.
The position of the gas venting choke was adjusted so as to keep the pressure upstream of the said choke at a value calculated according to the following formula as a function of the speed. of the motor:
Pgas 5 J3(V - Vmin) + Po if Vmin < V < Vmax
in which
Pgas represents the pressure upstream of the gas
venting choke,
V represents the target value of the speed of the
electric motor
p is a constant equal to -0.01
Po is a constant equal- to 20 bar
Vmin = 2740 rpm and Vmax = 3560 rpm, respectively
represent the minimum and maximum speeds of the
motor,
The thresholds for the current drawn by the electric motor for performing checks on this current were calculated by applying the following formulae:
Ihigh = INmin + y(V-Vmin) + dI if Vmin < V < Vmax
Ilow = INmin + y(V-Vmin) - Al if Vmin < V < Vmax in which:
Ihigh represents the high threshold for current drawn by the motor,
Ilow represents the low threshold for current drawn by the motor,
V represents the speed of the electric motor in rpm,
INmin 5 40 A represents the nominal minimum value of the current drawn by the motor,
Vmin = 3560 rpm and Vmax = 3560 rpm respectively represent the minimum and maximum values of the speed of the motor determined from the characteristics of the well, of the pump and of the motor, 7 = 0.034 and Al = 4 A are constants which were calculated for the well in question and which take account of the characteristics of the motor and of its actual cooling by the pumped hydrocarbons.
The stability of the current drawn by the motor was checked by making sure that the value of the said current did not exceed more than five times in one minute its mean value calculated over a period of time of 60 seconds, increased by 3 A, as in the starting phase.
When the target speed was reached, the production indicator, converted into an oil flow rate, was compared with the thresholds of 2400 and 3000 m3/ day.
The value to which the speed was reduced in the event of a crossing of a threshold for checking correct operation was equal to the value of the corresponding speed at the frequency of the supply current equal to 47 Hz, namely 2740 rpm.
During and after the starting phase, the very high and very low thresholds independent of the speed of the motor were equal to 80 A and 36 A respectively.
Claims (8)
- CLAIMS: Method of operating an oil and gas production well activated by a pumping system, comprising, placed at the wellbottom, a submerged pump (5) driven by an electric motor (6) which draws a known amount of current, the said well comprising, at its top, an oiloutlet choke (17) and a gas venting choke (22), characterized in that after a starting phase it consists in simultaneously performing the following operations: - increasing the speed of the motor (6) up to a predetermined target value, - opening the oil-outlet choke (17) up to a value that is calculated as a function of the target value of the speed of the motor (6), - acting on the gas venting choke (22) so as to keep the pressure upstream of the said choke at a value that is calculated as a function of the target value of the speed of the motor (6), - then checking for correct operation by performing checks on the current drawn by the motor (6) and on the well production, using production indicators.
- 2. Method according to Claim 1, characterized in that the extent to which the oil outlet choke (17) is open is calculated by applying the following formula: Soil P a(V - Vmin) + Smin if Vmin < V < Vmax in which: Soil represents the extent to which the oil outlet choke (17) is open V represents the target value of the speed of the electric motor (6) a is a constant Smin is a constant which represents the minimum extent to which the oil outlet choke (17) is open Vmin and Vmax respectively represent the minimum and maximum speeds of the motor (6), a, Smin, Vmin and Vmax are determined from characteristics of the well, of the pump (5) and of the motor (6).
- 3. Method according to Claim 1, characterized in that the pressure upstream of the gas venting choke (22) is calculated by applying the following formula: Pgas = ss(V - Vmin) + Po if Vmin < V < Vmax in which: Pgas represents the pressure upstream of the gas venting choke (22), V represents the target value of the speed of the electric motor (6), p is a constant Po is a constant Vmin and Vmax respectively represent the minimum and maximum speeds of the motor (6), ss, Po, Vmin and Vmax are determined from characteristics of the well, of the pump (5) and of the motor (6).
- 4. Method according to Claim 1, characterized in that with the current drawn by the motor (6) being compared with very high and very low thresholds independent of the speed of the motor (6), a crossing of one of the said thresholds causing the pump (5) to be stopped, the checks on the current drawn by the electric motor (6) for checking correct operation, additionally consist in: - comparing the value of the said current with high and low thresholds calculated as a function of the speed of the motor (6), - if a threshold is crossed, reducing the speed and if the threshold is still crossed, stopping the pump (5), - checking the stability of the said current, and if an instability is detected, reducing the speed to a predetermined value, and if the duration of the instability exceeds a predetermined value, stopping the pump (5).
- 5. Method according to Claim 4, characterized in that the high and low thresholds are calculated by applying the following formulae: Ihigh = INmin + y(V - Vmin) + Al if Vmin < V < Vmax Ilow = INmin + y(V - Vmin) - Al if Vmin < V < Vmax in which: Ihigh represents the high threshold for the current drawn by the motor (6), Ilow represents the low threshold for the current drawn by the motor (6), V represents the speed of the electric motor (6), INmin is a constant which represents the minimum nominal value of the current drawn by the motor (6), Vmin and Vmax respectively represent the minimum and maximum values of the speed of the motor (6) determined from characteristics of the well, of the pump (5) and of the motor (6), y and Al are constants calculated for each well from characteristics of the motor (6).
- 6. Method according to Claim 1, characterized in that the checks on the production of the well consist in taking as a production indicator at least one physical variable that indicates the oil outlet flow and in comparing the value of the said variable with at least one predetermined threshold, the threshold being considered as actually having been exceeded when it is so continuously for a predetermined duration, and if the threshold has been exceeded, in reducing the speed.
- 7 Method according to Claim 6, characterized in that the physical variable that indicates the oil outlet flow is chosen from the group consisting of a pressure difference created by a restriction on the oil outlet, the vent gas flow, the wellbottom pressure upstream of the pump (5), the pressure upstream of the oil outlet choke (17) and the oil outlet temperature.
- 8. Method according to any one of Claims 1 to 7, characterized in that with the well being equipped with a safety device, the method consists in closing the oil outlet and gas venting chokes (17 and 22) and in stopping the motor (6) immediately when the safety aevice comes into action.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9801782A FR2775018B1 (en) | 1998-02-13 | 1998-02-13 | METHOD OF CONDUCTING A WELL FOR PRODUCING OIL AND ACTIVE GAS BY A PUMPING SYSTEM |
| GB9902741A GB2334275B (en) | 1998-02-13 | 1999-02-09 | Method of operating an oil and gas production well activated by a pumping system |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9911625D0 GB9911625D0 (en) | 1999-07-21 |
| GB2334284A true GB2334284A (en) | 1999-08-18 |
| GB2334284B GB2334284B (en) | 2002-10-23 |
Family
ID=26234138
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9911625A Expired - Lifetime GB2334284B (en) | 1998-02-13 | 1999-02-09 | Method of operating an oil and gas production well activated by a pumping system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2334284B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2361352A (en) * | 2000-04-14 | 2001-10-17 | Schlumberger Holdings | A power cable for high temperature wellbore applications |
| GB2385076A (en) * | 2002-02-11 | 2003-08-13 | Abb Offshore Systems As | Integrated subsea power pack for drilling and production |
| GB2397833A (en) * | 2003-01-22 | 2004-08-04 | Weatherford Lamb | Control apparatus for automated downhole tools |
| WO2008124568A1 (en) * | 2007-04-06 | 2008-10-16 | Baker Hughes Incorporated | Systems and methods for reducing pump downtime by determining rotation speed using a variable speed drive |
| RU2471065C2 (en) * | 2010-08-05 | 2012-12-27 | Андрей Анатольевич Вахрушев | Development method of oil wells (versions), and plant for its implementation (versions) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2207161A (en) * | 1987-07-15 | 1989-01-25 | Otis Eng Co | Solenoid operated safety valve and submersible pump system |
| US5775879A (en) * | 1995-02-21 | 1998-07-07 | Institut Francais Du Petrole | Process and device for regulating a multiphase pumping assembly |
-
1999
- 1999-02-09 GB GB9911625A patent/GB2334284B/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2207161A (en) * | 1987-07-15 | 1989-01-25 | Otis Eng Co | Solenoid operated safety valve and submersible pump system |
| US5775879A (en) * | 1995-02-21 | 1998-07-07 | Institut Francais Du Petrole | Process and device for regulating a multiphase pumping assembly |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2361352A (en) * | 2000-04-14 | 2001-10-17 | Schlumberger Holdings | A power cable for high temperature wellbore applications |
| US6397945B1 (en) | 2000-04-14 | 2002-06-04 | Camco International, Inc. | Power cable system for use in high temperature wellbore applications |
| GB2361352B (en) * | 2000-04-14 | 2002-08-28 | Schlumberger Holdings | Power cable systems for use in high temperature wellbore applications |
| GB2385076A (en) * | 2002-02-11 | 2003-08-13 | Abb Offshore Systems As | Integrated subsea power pack for drilling and production |
| US7011152B2 (en) | 2002-02-11 | 2006-03-14 | Vetco Aibel As | Integrated subsea power pack for drilling and production |
| GB2385076B (en) * | 2002-02-11 | 2006-03-15 | Abb Offshore Systems As | Integrated subsea power pack for drilling and production |
| GB2397833A (en) * | 2003-01-22 | 2004-08-04 | Weatherford Lamb | Control apparatus for automated downhole tools |
| GB2397833B (en) * | 2003-01-22 | 2005-09-14 | Weatherford Lamb | Control apparatus for automated downhole tools |
| US7283060B2 (en) | 2003-01-22 | 2007-10-16 | Weatherford/Lamb, Inc. | Control apparatus for automated downhole tools |
| WO2008124568A1 (en) * | 2007-04-06 | 2008-10-16 | Baker Hughes Incorporated | Systems and methods for reducing pump downtime by determining rotation speed using a variable speed drive |
| US8092190B2 (en) | 2007-04-06 | 2012-01-10 | Baker Hughes Incorporated | Systems and methods for reducing pump downtime by determining rotation speed using a variable speed drive |
| RU2471065C2 (en) * | 2010-08-05 | 2012-12-27 | Андрей Анатольевич Вахрушев | Development method of oil wells (versions), and plant for its implementation (versions) |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9911625D0 (en) | 1999-07-21 |
| GB2334284B (en) | 2002-10-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PE20 | Patent expired after termination of 20 years |
Expiry date: 20190208 |