WO2024175941A1

WO2024175941A1 - Gas lock management

Info

Publication number: WO2024175941A1
Application number: PCT/IB2023/000063
Authority: WO
Inventors: Benoît GUILLERMOU; Louis-Claude LOEMBA; Diego SANCHEZ PUENTES; Céline BACQUET
Original assignee: TotalEnergies Onetech SAS
Current assignee: TotalEnergies Onetech SAS
Priority date: 2023-02-20
Filing date: 2023-02-20
Publication date: 2024-08-29
Anticipated expiration: 2025-08-20

Abstract

It is provided a computer system for gas lock management in a hydrocarbon production well equipped with an artificial activation system, the artificial activation system comprising an electrical submersible pump (ESP) the system. The system is configured to monitor an ESP motor current and an ESP frequency, detect a gas lock and determine a type of the gas lock, and manage the gas lock. The system forms an improved solution for gas lock management in a hydrocarbon production well equipped with an artificial activation system.

Description

GAS LOCK MANAGEMENT

Technical field

The present disclosure relates to the field of gas lock management in hydrocarbon production wells, and in particular a computer system, program and method for gas lock management in a hydrocarbon production well equipped with an artificial activation system, the artificial activation system comprising an electrical submersible pump (ESP) and a remote control valve (RCV).

Technical background

The ESP is designed to function using a maximum of fluid. For the ESP to function, the pump blades must create a pressure difference or delta, and for this need to rely on the liquid. The presence of gas in the ESP therefore poses a problem, causing the pump to accelerate and overheat. The motor may either reach a limit, and be forced to stop, or it may fail altogether. The ESP can also be equipped with a separator (for example a downhole separator, or a gas handler before the pump intake), however, the presence of too much gas can prevent it from effectively separating the liquid and gas streams.

Certain solutions exist for detecting and overcoming a gas lock. However, such methods are not sufficiently adapted to detect and handle different types of gas lock, especially those originating from gas pockets upstream of the ESP. For wells that have slightly horizontal or tilted segments (that is to say, for wells that are not fully vertical), gas can rest along the upper part of the segments and build up a gas pocket. This pocket may then appear in a sudden and rapid manner at the entry of the pump. Another type of gas lock that can occur is a build up of gas in the fluid, such as a stream of gas bubbles within the fluid occurring at the entrance of the pump, for example due to changes within the hydrocarbon reservoir or changes in height, the stream resulting in a proportion of gas versus liquid that is too high for the ESP to continue operating correctly.

Within this context, there is still a need for an improved system for gas lock management in a hydrocarbon production well equipped with an artificial activation system. Summary of the invention

It is therefore the object of this invention to provide a computer system for gas lock management in a hydrocarbon production well equipped with an artificial activation system, the artificial activation system comprising an electrical submersible pump (ESP) the system comprising:

- a memory having recorded thereon a production system computer program having instructions configured to, during a production phase based on a production target, cause a processor to: o monitor an ESP motor current and an ESP frequency; o detect a gas lock and determine a type of the gas lock among a pocket gas lock type corresponding to gas locks originating from gas pockets upstream of the pump and a continuous gas lock type; and o manage the gas lock, where:

■ for gas locks determined to be of the pocket gas lock type, the managing comprises temporarily increasing the ESP frequency to evacuate the gas locks, and

■ for gas locks determined to be of the continuous gas lock type, the managing comprises adjusting production so as to reduce risks of damaging the ESP;

- a processor coupled to the memory and configured to execute the program.

The system may comprise one or more of the following features:

- the adjusting production comprises adjusting a controllable parameter value of the production well to meet a new target parameter value;

- the processor is configured to: o determine the continuous gas lock type when a motor current presents periodical oscillations, with ascending peaks being above a first predetermined threshold over a first predetermined period of time and/or descending peaks being below a second predetermined threshold over the first predetermined period of time, while the ESP frequency remains stable; and o determine the pocket gas lock type when the motor current reaches a third predetermined threshold over a period of time lower than a second predetermined period of time, while the ESP frequency remains stable, or when the motor current presents periodical oscillations with ascending peaks above a first predetermined threshold over a first predetermined period of time and/or descending peaks below a second predetermined threshold over the first predetermined period of time, while the ESP frequency remains stable;

- the periodical oscillations comprise from 2 to 10 peaks, for example 3 peaks, the first predetermined period of time ranging from 10 seconds to 2 minutes, for example, 60 seconds;

- the first predetermined threshold is of the order of 2A, or of 3A, more than the initial current value, for example, the first predetermined threshold being equal to 2A, or 3A, more than the initial current value and the second predetermined threshold is of the order of 2A, or of 3A, less than the initial current value, for example, the second predetermined threshold being equal to 2A, or 3A, less than the initial current value;

- the at least one third predetermined threshold corresponds to a change in motor current lying from 0.5 to 20% of an initial motor current and the second predetermined period of time lies between 1 and 5 minutes or less than or equal to 30 seconds or greater than or equal to 30 seconds, for example the third predetermined threshold being 5% of the initial motor current and the second predetermined period of time being greater than or equal to 2 minutes, or for example the third predetermined threshold being 1 % of the initial motor current and the second predetermined period of time being greater than or equal to 24 seconds, or for example the third predetermined threshold lying from 10 to 15% of the initial motor current and the second predetermined period of time being greater than or equal to 15 seconds;

- the processor is further configured to monitor a tubing density, the determining of a pocket gas lock type occurring when the tubing density reaches at least one fourth predetermined threshold over a period of time lower than at least one third predetermined period of time;

- the at least one fourth predetermined threshold corresponds to a change in tubing density lying from 3% to 12% of an initial tubing density, for example from 5% to 10% of an initial tubing density, and the at least one third predetermined period of time is greater than or equal to 1 min or less than or equal to 60 s, for example between 30 seconds and 90 seconds;

- the processor is further configured to monitor an ESP discharge pressure, the determining of a pocket gas lock type occurring when the pump discharge pressure system reaches at least one fifth predetermined threshold over a period of time lower than at least one fourth predetermined period of time;

- the at least one fifth predetermined threshold corresponds to a change in discharge pressure lying from 3% to 12% of the initial discharge pressure, for example from 5% to 10% of the initial discharge pressure , and the at least one fourth predetermined period of time is greater than or equal to 60 s and/or less than or equal to 60 s, for example between 30 s and 90 s;

- the system further comprises an alarm configured to sound upon detection of the gas lock;

- for gas locks determined to be of the pocket gas lock type, to manage the gas lock, the production target is set to motor frequency (MF) or wellhead temperature (WHT) and the processor is further configured to: o save a motor frequency value; o reduce the motor frequency value to an motor frequency setpoint value; o ramp down a choke opening setpoint value to a choke setpoint value; o adjust a pressure control valve (PCV) to maintain a casing head pressure (CHP) regulation; o launch a timer; o increase the motor frequency setpoint value to a frequency higher than the saved motor frequency value so as to evacuate the gas lock;

- for the adjusting production, the production target is set to bottom hole pressure (BHP) and the processor is configured to repeatedly: a) check if a choke opening value is greater than a choke heel value; b) confirm a new well head pressure target value is less than a maximum gas lock well head pressure; c) adjust the choke opening value to reach the well head pressure target value; d) upon reaching the well head pressure target value, adjusting the motor frequency to reach a bottom hole pressure target value; e) adjust the motor frequency to reach a new gas lock BHP target value; f) launch a timer; g) when the timer lapses, launch a check to see if the motor current is presenting periodical oscillations with ascending peaks above a first predetermined threshold over a first predetermined period of time and descending peaks below a second predetermined threshold over the first predetermined period of time; and h) if the oscillations are present, repeat steps a) to g),

- the processor is further configured to inform the operator of the type of the gas lock detected; and/or

- the program is configured to receive an operator validation upon completion of the evacuation of the gas lock.

It is also provided a computer program comprising instructions installable on a memory coupled to a processor so as to form the computer system for gas lock management.

It is also provided a data storage medium having recorded thereon the computer program according.

It is also provided a method for gas lock management in a hydrocarbon production well equipped with an artificial activation system, the artificial activation system comprising an electrical submersible pump (ESP), the method comprising:

- providing a computer system according to the system; and

- executing the computer program so as to, during a production phase based on a production target, cause the processor to: o monitor an ESP motor current and an ESP frequency; o detect a gas lock and determine a type of the gas lock among a pocket gas lock type corresponding to gas locks originating from gas pockets upstream of the pump and a continuous gas lock type; and o manage the gas lock, where:

■ for gas locks determined to be of the pocket gas lock type, the managing comprises, temporarily increasing the ESP frequency to evacuate the gas locks, and for gas locks determined to be of the continuous gas lock type, the managing comprises, adjusting production so as to reduce risks of damaging the ESP.

Brief description of the drawings

Non-limiting examples will now be described in reference to the accompanying drawings, where:

FIG. 1 shows an example of a gas pocket upstream of the ESP;

FIG. 2 shows an example of a hydrocarbon production well equipped with an ESP;

FIG. 3 shows schematic diagram illustrating an example of the system;

FIG. 4 shows a graph displaying current intensity as a function of time, according to an example of the system;

FIG. 5 shows an example of a user interface of the system;

FIG. 6 shows an example of the computer system;

FIG. 7 shows a graph displaying current intensity as a function of time, according to an example of the system;

FIG. 8 shows an example of a graph displaying tubing density as a function of time, according to an example of the system; and

FIG. 9 shows an example of a graph displaying pump discharge pressure as a function of time, according to an example of the system.

Detailed description

It is provided a computer system for gas lock management in a hydrocarbon production well equipped with an artificial activation system. The artificial activation system comprises an electrical submersible pump (ESP).

The system comprises a memory having recorded thereon a production system computer program. The computer program has instructions configured to, during a production phase based on a production target, cause a processor to execute functionalities supported by the system. The instructions are configured to cause the processor to monitor an ESP motor current and an ESP frequency. The instructions are configured to cause the processor to detect a gas lock and determine a type of the gas lock among a pocket gas lock type corresponding to gas locks originating from gas pockets upstream of the pump and a continuous gas lock type. The instructions are configured to cause the processor to manage the gas lock, where for gas locks determined to be of the pocket gas lock type, the managing comprises temporarily increasing the ESP frequency to evacuate the gas locks. The instructions are configured to cause the processor to manage the gas lock, where for gas locks determined to be of the continuous gas lock type, the managing comprises adjusting production so as to reduce risks of damaging the ESP. The system comprises a processor coupled to the memory and configured to execute the program.

It is also provided a method for gas lock management in a hydrocarbon production well equipped with an artificial activation system, the artificial activation system comprising an electrical submersible pump (ESP, also referred to as ESP system). The method comprises providing the system and executing the computer program so as to, during a production phase based on a production target, cause the processor to execute the functionalities supported by the system in relation to gas lock management as discussed hereinabove and hereinbelow.

Such a system and method form an improved solution for gas lock management in a hydrocarbon production well equipped with an artificial activation system.

The production phase (i.e. a phase after the start-up phase) is based on a production target. In other words, the system allows for the execution of production while maintaining a given production parameter at a desired value, i.e. a production target, and thereby regulate production. The production target may change depending on the type of gas lock determined by the system, so as to better manage the gas lock. By the processor being configured by the program to, during a production phase based on a production target, monitor an ESP motor current and an ESP frequency, the system can observe any fluctuations or irregularities in the current and frequency. The production target may be a bottom hole pressure (BHP) target or another target. The system may detect a gas lock and determine the gas lock to be of a continuous gas lock type. The detection and determination of the gas lock type may be independent of the selected production target. The system may manage the continuous gas lock type when the selected production target is BHP. Alternatively, the system may detect a gas lock and determine the gas lock to be of a pocket gas lock type. For a pocket gas lock type, the managing may comprise adjusting production when the selected production target is a target other than BHP. The system may work to reach the production target and may maintain the target over a period of time. The system may adjust production in a manner such that the adjusting production comprises adjusting a controllable parameter value of the production well to meet a new target parameter value. In other words, the adjusting may comprise indirectly adjusting the production target value to meet a new target parameter value. This allows for a versatile system that can be easily controlled. For example, if the production target is BHP, the corresponding controllable parameter may be pump/ESP frequency or pump/ESP motor frequency (which may control the pump frequency, i.e. the pump/ESP motor frequency, or motor frequency of the pump/ESP, may refer to the frequency for the motor, and the pump may be connected with for example a direct connection on the motor so it is the same).

During the working to reach the production target and the maintaining of the target, the system may monitor the ESP motor current and ESP frequency. The system may additionally, during the working or maintaining, detect a gas lock, determine the type of gas lock, and manage the gas lock. This may comprise reducing or increasing production, which may cause the system to stray from its production target.

The system may detect a gas lock and determine the gas lock to be of a continuous gas lock type. In such a case, to manage the gas lock, the system may have BHP as the selected production target. Alternatively, the system may detect a gas lock and determine the gas lock to be of a pocket gas lock type. Selecting the production target may comprise an operator action. The operator may change the selected production target to be a BHP production target (if the selected target is not already BHP) if the system determines a continuous gas lock type. The operator may change the selected production target to be a production target other than BHP (if the selected target is BHP) if the system determines a pocket gas lock type. The system may notify the operator of the detected gas lock and the type of gas lock determined, and the operator may then change the production target to BHP in the case of a determined continuous gas lock type, or the operator may change the production target to another production target (for example, motor frequency (MF) or wellhead temperature (WHT)) in the case of a determined pocket gas lock type.

The processor may detect when the gas lock has been sufficiently managed (i.e., when monitoring the ESP motor current and ESP frequency, the system no longer detects a gas lock). Upon detecting that the gas lock has been sufficiently managed, the processor may execute computer program instructions to one or more parameters so as to aim for the production target once more. Upon completion of the managing of the gas lock, the system may work once again during the production phase to achieve, and optionally maintain, the production target.

Optionally, the managing of the gas lock during the working and maintaining may comprise adjusting production for gas locks of a continuous gas lock type. This may comprise reducing production (for example by reducing ESP frequency) so as to reduce risks of damaging the ESP. The system may then optionally increase production to achieve the target value once the adjusting is completed. Alternatively, this may comprise increasing production (for example by increasing ESP frequency) so as to reduce risks of damaging the ESP. The system may then optionally decrease production to achieve the target value once the adjusting is completed.

Optionally, the managing of the gas lock during the working and maintaining may, for a gas lock of a gas lock pocket type, comprise temporarily increasing the ESP frequency to evacuate the gas locks. The system may then optionally decrease production to achieve the target value once the adjusting is completed.

The processor/system may detect a gas lock (at the pump) based on information obtained at the pump and may then determine a type of gas lock. Consequently, the system can apply appropriate measures to overcome the gas lock that are specific to the detected gas lock type. The processor may detect the gas lock as it arrives at and/or enters the pump. Additionally or alternatively, the processor may perform an early detection of a gas lock. In other words, the processor may detect the presence of gas at the entrance of the pump and/or within the pump which may indicate the beginning of formation of a gas lock at the pump prior to its actual formation at the pump.

The system may be used in a method for gas lock management in a well having one or more such horizontal or non-vertical segments (i.e., mean angle with the horizontal plane, that is, perpendicular to gravity, below a predetermined threshold which may lie between 1 degree and 30 degrees). The well may comprise one or more bends. The bends may connect a vertical segment with a non-vertical segment, or a non-vertical segment and a vertical segment. Each segment of the well may be of an equal diameter. The one or more horizontal or non-vertical segments and/or bends may cause a pressure difference between different points along the well and may therefore cause the formation of a gas pocket along the well, for example upstream of the pump. The well may extend through a wellbore, the wellbore comprising a rock material such as, for example for example, limestone or sandstone. The method may be used during one or more production phases of such a well, wherein in at least one production phase a gas lock of the pocket gas lock type occurs and is detected and determined as such by the processor. Optionally, in at least one other production phase, a gas lock of the continuous type occurs and is detected and determined as such by the processor. The expression “production phase” refers to a period of time where hydrocarbon (e.g., oil and/or gas) is being produced from the well. The well may be a ventilated well or a non ventilated well. Depending on the type of well, the hydrocarbon production well may be equipped with various different actuators. For example, for a ventilated well, the well may be equipped with an actuator individually configurable as installed or not installed, such as a downhole safety valve (DHSV), production master valve (PMV), production wing valve (PWV), annulus safety valve (ASV), annulus master valve (AMV), pressure control valve (PCV) and/or an annulus wing valve (AWV). The ventilated well may always be installed with an RCV. According to another example, for a non ventilated well, the well may be equipped with an actuator individually configurable as installed or not installed, such as a downhole safety valve (DHSV), production master valve (PMV) and/or a production wing valve (PWV). The non ventilated well may always be installed with an RCV.

The gas pockets are upstream of the pump. The pockets may appear in a slightly horizontal or tilted (that is to say, not fully vertical) segment of the well, the gas resting along the upper part of the segment and building up to form the gas lock pocket. The gas lock may be a quantity of gas that is sufficient to slow or stop the pumping of well fluids to the surface of the hydrocarbon production well. The event can occur due to the gas sufficiently replacing the fluid pumped by the ESP to the surface. Notably, by detecting the gas pocket upstream of the pump, the system can react in sufficient time of the gas lock reaching the pump and therefore more effectively protect the ESP. The system can then apply measures appropriate to the gas lock type specifically.

The gas lock may be of a pocket type or of a continuous type. The system may determine a continuous gas lock type. A continuous gas lock type may correspond to other types of gas locks (i.e. other than a gas lock pocket type), which are continuously observable in the ESP, and that may appear even in the absence of gas pockets upstream of the pump. If a continuous gas lock type is determined, managing the gas lock by adjusting production may cause the production target, for example BHP, to increase above or decrease below its target value. The production target may be intended for optimizing the production. However, the processor may pause any efforts made by the system to achieve the desired production target value so as to instead manage the gas lock. Upon completion of the adjusting, the processor may execute instructions for the system to once again work to achieve the production target value, for example the BHP target value. The continuous gas lock type may be in the form of a stream of gas bubbles throughout a volume of the well fluid. The continuous gas lock type may occur for example due to changes within the hydrocarbon reservoir or changes in height, the stream resulting in a proportion of gas versus liquid that is too high for the ESP to continue operating correctly.

The system may determine a pocket gas lock type. The pocket gas lock type may be in the form of a continuous volume of gas. FIG. 1 displays an example of such a pocket 100 along a horizontal section 104 of a well 106, the pocket being present as upstream of the pump 102 (arrow 108 indicating the direction of fluid flow). The pocket forms just after a first bend 103 and before a second bend 105. The formation of the pocket may be caused by a pressure difference between the horizontal segment 104 and the previous vertical segment 107. Such a pocket may then appear in a sudden and rapid manner at the entry of the pump.

According to another example, if the system determines a pocket gas lock type, it may, like in the case of the continuous gas lock type, apply measures appropriate to a gas lock pocket type specifically. The managing of the pocket gas lock type may comprise the selected production target being another target (i.e. other than BHP). The production target may be a parameter of the hydrocarbon production well or the well equipment, such as motor frequency (MF), or wellhead temperature (WHT). If a pocket gas lock type is determined when the target is MF, WHT, or any other production target parameter, managing the gas lock may comprise selecting the target to be MF, WHT, (if not already selected) or another production target parameter (if not already selected) other than BHP, before adjusting production. Adjusting production may cause the target parameter to increase above its target value. Adjusting production can allow for the a new operating point where (i.e. of the system or part of the system, e.g. of the ESP), by for example reducing production, the gas/liquid ratio can be acceptable to the ESP. The processor may pause any efforts made by the system to achieve the production target value. Upon completion of the adjusting, the processor may execute instructions for the system to once again work to achieve the production target.

By the production system being configured to, during a production phase based on a production target set as a bottom hole pressure target or a another target, manage the gas lock, the system can effectively protect the ESP, regulate production and therefore optimize production. The ESP may provide an artificial-lift method for lifting volumes of fluids from the well. The ESP may run during production so as to pump well fluid to the surface. The artificial activation system may comprise a second ESP which can act as a back up ESP, for example in the case of failure of the first ESP. The ESP, also referred to as the ESP assembly, may comprise a pump (for example a multistaged centrifugal pump), a motor (for example, a three-phase induction motor) and a seal-chamber section. The motor may be attached below the pump. A power cable may connect the ESP to the processor and/or surface controls above the well. A VSD (variable speed drive) may power the ESP. The VSD may control the pump/ESP motor frequency. The processor may send a command to the VSD, for example via an actuator, to start the running of the ESP. The computer program has instructions configured to cause the processor to monitor ESP frequency. The ESP frequency may be the frequency of the pump. The motor frequency may control the ESP frequency. The ESP may have a minimal frequency, for example at the start of production. The frequency may increase to a regulated flow rate during production. Performing a stopping of the ESP, for example due to a critical gas lock detection, may comprise reducing the ESP frequency back to a minimal frequency before stopping the ESP. The computer program has instructions configured to cause the processor to monitor ESP motor current. The monitoring of the ESP frequency and/or ESP motor current may be by one or more sensors for each of the frequency and current respectively. One or more ESP motor current sensors may be positioned at the motor, the one or more sensors being for example for motor winding temperature, and/or motor vibrations. The one or more sensors may check that the motor is working within its recommended operating range. The one or more sensors may measure pressure and/or temperature at the pump intake and discharge to evaluate pump performance. One or more ESP frequency sensors may be positioned along the pump, for example at the entrance to the pump and/or at the exit of the pump. Additionally or alternatively, one or more ESP frequency sensors may be positioned along the motor. The sensors may measure the displacement and/or speed of the motor as it rotates. The processor may calculate the frequency of the ESP (i.e. of the pump) using the measurements obtained at the motor. The one or more sensors may take measurements at a predefined sampling rate.

Monitoring an ESP motor current and an ESP frequency may comprise the processor reading in values of ESP motor current and ESP frequency. The processor may continuously read in measurement values obtained by ESP motor current and ESP frequency sensors over a predefined period of time, or for example, continuously during the running of the program. The monitoring may comprise the processor checking to see if the values satisfy any conditions related to gas lock detection by comparing the values to a threshold. The monitoring may comprise the processor checking to see if the values satisfy any conditions related to gas lock detection by comparing the values to a threshold and checking if the threshold is met over a predefined period of time. The system may detect the gas lock and determine the gas lock type using the monitored ESP motor current and ESP frequency. If during the monitoring a certain number of preconditions are met, the system may detect the presence of a gas lock and its type.

The system may comprise a separator (for example a downhole separator, or a gas handler before the pump intake). Protecting the ESP can also facilitate the work of the separator. The system can directly manage the complexities posed by each gas lock type. For gas locks determined to be of the pocket gas lock type upstream of the pump, the managing comprises, temporarily increasing the ESP frequency to evacuate the gas locks. This enables both protecting the ESP and reducing a need for stopping the ESP. For gas locks determined to be of the continuous gas lock type, the managing comprises, adjusting production so as to reduce risks of damaging the ESP. This in turn also enables reducing risks of stopping the ESP and so can regulate and optimize production. The adjusting also enables straying from the production target as little as possible, so as to continue to produce as much hydrocarbons as possible.

A processor is coupled to the memory and is configured to execute the program. The processor may also be coupled to a graphical user interface (GUI) of the system. The program is recorded on the memory. The memory may also store a database. The memory may be any hardware adapted for such storage, possibly comprising several physical distinct parts (e.g. one for the program, and possibly one for the database). It is also provided a computer program comprising instructions installable on a memory coupled to a processor so as to form a computer system for gas lock management according to any one of claims 1 to 14.

The computer program may comprise instructions executable by a computer, the instructions comprising means for causing the above system to perform the method. The program may be recordable on any data storage medium, including the memory of the system. The program may for example be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The program may be implemented as an apparatus, for example a product tangibly embodied in a machine-readable storage device for execution by a programmable processor.

Method steps may be performed by the processor (e.g. a programmable processor), executing the program having instructions to perform functions of the method by operating on input data and generating output. The input data may comprise the monitored ESP motor current and ESP frequency. The output may comprise a communication that the system detects a gas lock, the type of gas lock, and the execution of instructions to manage the gas lock. The processor may thus be programmable and coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. The application program may be implemented in a high-level procedural or object- oriented programming language, or in assembly or machine language if desired. In any case, the language may be a compiled or interpreted language.

The program may be a full installation program or an update program. Application of the program on the system results in instructions for performing the method. The computer program may alternatively be stored and executed on a server of a cloud computing environment, the server being in communication across a network with one or more clients. In such a case when the processor or processing unit executes the instructions comprised by the program, it causes the method to be performed on the cloud computing environment.

The processor may be configured to determine a continuous gas lock type when a number of continuous gas lock conditions are met. These conditions may include the motor current presenting periodical oscillations with ascending peaks above a first predetermined threshold over a first predetermined period of time and descending peaks below a second predetermined threshold over the first predetermined period of time. Each peak may be considered to have reached a respective threshold (i.e. the first predetermined threshold or second predetermined threshold) when the maximum value of the peak (i.e. the apex of the peak) reaches or exceeds the threshold. The ESP frequency may meanwhile remain stable. This may be so as to ensure that the frequency is not causing the periodical oscillations. The oscillations allow for an indication that the frequency is unstable. Detecting such a motor current instability allows for detecting an excessive gas presence at the pump level. Current can be a good representative parameter of the pump load. As soon as gas is present, the current may become unstable, i.e. may exhibit periodical oscillations. The periodical oscillations may comprise from 2 to 10 peaks, for example 3 peaks. Alternatively, the periodical oscillations may comprise a different range of peaks. The range of peaks may depend on the well and/or the ESP. The first predetermined period of time may range from 10 seconds to 2 minutes, for example, 60 seconds. The processor may detect an oscillation for each consecutive positive and negative peak that meet a respective current threshold value. Alternatively, the processor may detect an oscillation for a consecutive number of positive peaks meeting a positive threshold value. Alternatively, the processor may detect an oscillation for a consecutive number of negative peaks meeting a negative threshold value.

When the current exceeds a value higher than the first predetermined threshold (also referred to as maximum permissible threshold or XXI_H parameter), for example, 5 times this threshold per minute (the first predetermined period of time), the system may trigger a fault alarm (almXXI_H). The processor may calculate the current ramp to evaluate the peak height. If the motor current ramp is positive the processor may calculate the maximum value of current. If the motor current ramp is negative, the processor may calculate the minimum value of current. The processor may use the differences between these values to determine the peak height. The processor may memorize the calculated current on a FIFO (first in first out) basis.

When the system detects the continuous gas lock, it may send a dedicated alarm to the operator, for example via the GUI. The system may detect a gas lock based off the monitoring of an ESP motor current and an ESP frequency. The adjusting may therefore be as a function of the monitored ESP frequency and ESP motor current. The adjusting production to reduce risks of damaging the ESP may comprise finding a new operating point or operating mode. This may enable finding a new operating point where, by for example reducing production, the gas/liquid ratio can be acceptable to the ESP (i.e. the ESP may continue to correctly function). The managing of the continuous gas lock may therefore also assist in preventing further formation of a gas lock of the same kind. Adjusting production may comprise increasing or reducing production, i.e. increasing or reducing the rate of production (for example, by increasing or reducing ESP motor frequency). Reducing risks of damaging the ESP may comprise slowing or increasing production and thereby preventing the ESP from overheating in trying to pump a fluid which is not present (having been replaced by the gas lock). Adjusting production may comprise adjusting a controllable parameter value of the production well to meet a new target parameter value. The controllable parameter may be a different parameter to the target parameter, but one that is related to the target parameter (e.g. pump/ESP frequency and BHP as the controllable parameter and target parameter respectively). The system may adjust production by adjusting the opening of the choke (i.e. valve, e.g. remote control valve (RCV)) so as to increase the wellhead pressure (WHP). The adjusting may comprise adjusting the choke until the WHP reaches a target WHP. The adjusting may comprise reducing the opening of the choke valve. Consequently, at least some of the gas can be evacuated and the gas lock impact can be reduced. If the system comprises a separator (i.e. a downhole separator), the system may reduce the choke opening from the full opening of the choke (e.g. RCV opening) to greater than or equal to 65% of the full opening of the choke (i.e. the choke being fully open at 100%) so as to increase WHP. For example, as a result of reducing the opening of the choke valve, the system may increase production by 1 % to 5%, for example 2%, or for example 3%. If the system does not comprise a separator (i.e. a downhole separator), the system may reduce choke opening (e.g. RCV opening) to less than or equal to 65% of the full opening of the choke. In other words, if the system does not comprise a separator, the adjusting may comprise choking the well (i.e. reducing the opening of the choke) more so than in the case where the system comprises a separator. For example, the system may increase production by 1 % to 5%, for example 2%, or for example 3%.

To manage a continuous gas lock type, the production target may be set to bottom hole pressure (BHP). The program may comprise instructions for the processor to run an automatic loop of steps for the adjusting. The processor may repeatedly execute the steps for adjusting the production. The steps may include actions on the choke (i.e. valve, e.g. remote control valve (RCV)). Upon detection, the processor may automatically adjust the target value so as to overcome the gas lock (i.e. may continue the regulation with the updated target value). The processor may repeatedly (i.e. for each iteration of the loop) check if choke opening value is greater than a choke heel (e.g. RCV_Heel) value. In other words, the processor may check to see if the choke is open (e.g. greater than RCV heel) or closed (e.g. RCV heel).

The processor may repeatedly (i.e. for each repetition of the loop) confirm a new WHP target value (GL_WHP_target) is less than a maximum gas lock well head pressure (GL_WHP_max). The processor may repeatedly adjust the RCV opening value to reach the well head pressure target value. With each repetition, the new WHP target may be equal to WHP_Target+dP_WHP_GL x N, dP_WHP_GL being the change in wellhead pressure to overcome the gas lock and N being the number of repetitions (the regulation starting with N=1 ). The processor may at this point adjust a pressure control valve (PCV) so as to maintain a casing head pressure (CHP) regulation. In other words, the processor may keep a PCV setpoint equal to a CHP target (PCV set point = CHP_Target). The processor may define a gas lock wellhead pressure target limit (GL_WHP_limit) to be greater than a wellhead pressure limit (WHPJimit). In other words, the processor may apply a new higher WHP limit to the WHP limiter. This may protect the WHP from reaching too great a pressure (as if the WHP is too high, this may prevent the well from producing) when overcoming the gas lock, but also enabling the pressure to overcome the usual WHP limit (i.e. the limit when there is no gas lock). The processor may define the gas lock wellhead pressure target limit, or “protection threshold”, to protect the well and its equipment. It may have priority over all other parameters of the system. The program may monitor the limit continuously, and if it detects that it has been reached, it may perform a progressive adjustment of the RCV opening to maintain the WHP below the gas lock wellhead pressure target limit.

The program may comprise instructions for the processor to then execute a gas lock frequency fallback phase. This may include continuing the regulation while also modifying certain production target values. The system may have a pump frequency setpoint that uses the (pump, also referred to as ESP) motor frequency to maintain the BHP target. However, for the adjusting, the processor may repeatedly (i.e. for each repetition of the loop), upon reaching the wellhead pressure target value, adjust or regulate the motor frequency to reach a new gas lock BHP target value. In other words, the processor may modify a pump frequency setpoint to change the BHP. The new gas lock BHP target may be equal to [BHP_Target] + [dP_BHP_GL] x N, dP_BHP_GL, dP_BHP_GL being the change in bottom hole pressure for overcoming the gas lock, and N being the number of repetitions (regulation starting with N=1 ). The processor may define an updated gas lock motor frequency target limit (GL_MF_limit) to be greater than a motor frequency limit (MFJimit, or “MF_target” for an operator). The processor may define the gas lock motor frequency target limit, or “protection threshold”, to protect the well and its equipment. It may have priority over all other parameters of the system. The processor may monitor the limit continuously, and if it detects that it has been reached, it may perform a progressive adjustment of the motor frequency to maintain the MF below the gas lock motor frequency limit (GL_MF_limit).

When the BHP reaches a new BHP, the program may comprise instructions for the processor to launch a sequence of gas lock stabilization control. Each time (i.e. repeatedly) the WHP reaches its target, and BHP reaches its target (i.e. once both targets have been reached), the processor may launch a timer. The processor may launch the timer with a gas lock delay (GL_D) target to observe the motor current stability. The GL_D may be a parameter for the timer, set for example by the operator in minutes. The processor may launch the timer (GL_D) to observe the motor current stability. The processor may implement this observing until the timer lapses. Observing motor current stability may comprise launching a check to see if the motor current is presenting periodical oscillations with ascending peaks above a first predetermined threshold over a first predetermined period of time and descending peaks below a second predetermined threshold over the first predetermined period of time. In other words, the first predetermined threshold may be a predetermined increase (“+”) above an initial current value. The second predetermined threshold may correspond to a predetermined decrease (“-“) below an initial current value. The first predetermined threshold may be of the order of 2A, or of 3A, more than the initial current value. For example, the first predetermined threshold may be equal to 2A, or 3A, more than the initial current value. The second predetermined threshold may be of the order of 2A, or of 3A, less than the initial current value. For example, the second predetermined threshold may be equal to 2A, or 3A, less than the initial current value. The initial motor current value may be a baseline value of motor current, or a nominal value of motor current. The initial motor current may have a value of, for example 32A (which may for example correspond to an ESP intensity of 45 Hz). If the motor current is still not stable (i.e. if the motor current is presenting periodical oscillations with ascending peaks above a first predetermined threshold over a first predetermined period of time and descending peaks below a second predetermined threshold over the first predetermined period of time), the processor may execute the loop once again, adding a new count to N (N+1 ). Additionally, if the motor frequency reaches the gas lock motor frequency limit, the program may comprise instructions for the processor to raise an alarm and may launch a deactivation mode (i.e. the system may stop the ESP). Additionally or alternatively, if the WHP reaches the gas lock WHP limit, the processor may raise an alarm and may launch a deactivation mode (i.e. the system may stop the ESP).

If, however, the motor current is stable (i.e. no continuous gas lock conditions are met), the processor may inform the status operator (for example, via the GUI). The processor may deliver a message indicating which parameters of the system should be updated following the end of detection, before continuing normal regulation. In other words, the system may warn the panel operator that targets (e.g. BHP, WHP) and limits should be updated and that motor current-related parameters should be checked. The parameters listed by the parameter may be for indication only. Parameters that the operator may update may include, for example, WHP_target, BHP_target, MF_target, BHPJimit, WHPJimit, motor current limit (MCJimit), motor current low (MC_L), motor current high (MC_H), motor current low low (MC_LL), and/or motor current high high (MC_HH). The system may require an operator acknowledgement before continuing the regulation.

The processor may determine a pocket gas lock type when a number of pocket gas lock conditions are met. These conditions may include the processor monitoring the motor current for periodical oscillations with ascending peaks above a first predetermined threshold over a first predetermined period of time and/or descending peaks below a second predetermined threshold over the first predetermined period of time, while the ESP frequency remains stable. In other words, the first predetermined threshold may be a predetermined increase (“+”) above an initial current value. The second predetermined threshold may correspond to a predetermined decrease (“-“) below an initial current value. The first predetermined threshold may be of the order of 2A, or of 3A, more than the initial current value. For example, the first predetermined threshold may be equal to 2A, or 3A, more than the initial current value. The second predetermined threshold may be of the order of 2A, or of 3A, less than the initial current value. For example, the second predetermined threshold may be equal to 2A, or 3A, less than the initial current value. The initial motor current value may be a baseline value of motor current, or a nominal value of motor current. The initial motor current may have a value of, for example 32A (which may for example correspond to an ESP intensity of 45 Hz). Like for detecting the continuous gas lock, the oscillations may comprise from 2 to 10 peaks, for example 3 peaks, the first predetermined period of time ranging from 10 seconds to 2 minutes, for example, 60 seconds.

Additionally or alternatively, the conditions for the determining may be met if the motor current reaches at least one third predetermined threshold (e.g. a sudden current decrease threshold) over a period of time lower (less than) than at least one second predetermined period of time. The conditions may be fulfilled if the current reaches the threshold instantaneously or almost instantaneously. The at least one third predetermined threshold may correspond to a change (e.g. a decrease) lying from 0.5 to 20% of the initial motor current (i.e. the value of the current immediately before the period of time lower than the at least one second predetermined period of time). In other words, the at least one third predetermined threshold may be equal to the difference between an initial current value and a certain percentage of the initial current value (e.g. lying from 0.5 to 20% of the initial motor current value). The initial motor current value may be a baseline value of motor current, or a nominal value of motor current. For example, the initial motor current may change by 2% to 5% of the initial motor current, for example 3% of the initial motor current, or for example 5% of the initial motor current, the motor current being generally a very steady parameter. The second predetermined period of time may lie between 1 and 5 minutes or less than or equal to 30 seconds or greater than or equal to 30 seconds. For example, the third predetermined threshold may correspond to a change of 5% of the initial motor current and the second predetermined period of time may be greater than or equal to 2 minutes. Alternatively, for example, the third predetermined threshold may correspond to a change of 1 % of the initial motor current and the second predetermined period of time may be greater than or equal to 24 seconds. Alternatively, for example, the third predetermined threshold may correspond to a change lying from 10 to 15% of the initial motor current and the second predetermined period of time may be greater than or equal to 15 seconds. Alternatively, the third predetermined threshold may correspond to a change of less than 10% of the initial motor current or greater than 15% of the initial motor current. The second predetermined period of time may be greater than or equal to 10 seconds.

The second predetermined period of time may be a sliding interval. The second predetermined period of time may be considered to be a period of time that is part of repeated process run by the system, i.e. the second predetermined period of time may be measured (or may run) several times while the motor is running. For example, the second predetermined period of time may be measured at a predetermined sampling rate during the running of the motor. Second predetermined periods of time may overlap within one another. In other words, an “initial” second predetermined period of time may start running, and may be followed by a “second” predetermined period of time which may start running while the “initial” second period of time is still running. Likewise, a “third” predetermined period of time which may start running while the “second” second period of time is still running, and even when then the “first” second period of time is still running. Second predetermined periods of time may start running consecutively, but may run while a previous second period of time is still running. This way, when the motor current reaches the third predetermined threshold, the moment of reaching the third predetermined threshold may be captured within one of the second predetermined periods of time. A successful second predetermined period of time may therefore be considered to be the first (not necessarily “initial”) second predetermined period of time that captures the moment at which the current reaches the third predetermined threshold.

Additionally or alternatively, the conditions for determining a pocket gas lock type may include the processor monitoring a tubing density. Detecting a gas lock by monitoring the tubing density may enable detecting a gas lock of a pocket type. The condition may be fulfilled if the tubing density reaches at least one fourth predetermined threshold over a period of time lower than at least one third predetermined period of time. Like the second predetermined period of time, the third predetermined period of time may be a sliding interval. The at least one fourth predetermined threshold may correspond to a change (e.g. a decrease) in tubing density lying from 3% to 12% of an initial tubing density, for example from 5% to 10% of an initial tubing density. In other words, the at least one fourth predetermined threshold may be equal to the difference between an initial tubing density value and a certain percentage of the initial tubing density value (e.g. lying from 3 to 12% of the initial tubing density value). The initial tubing density value may be a baseline value of tubing density, or a nominal value of tubing density. The at least one third predetermined period of time may be greater than or equal to 60 s (1 min) and/or less than or equal to 60 s, for example between 30 s and 90 s. For example, taking a tubing density reference of 600 kg/m³ psi, if in less than 1 min the discharge pressure comes from 600 to 640 kg/m³, the system may determine a pocket gas lock type.

The tubing density (or, the effluent density in the tubing (DT_GL)) may be calculated from the pressure difference between the tubing head pressure and the discharge pressure of the pump (AP = PDP - WHP), from the difference height (H) between two pressure sensors (the sensors may be positioned at different locations along the well), and from the gravitational constant g and the corrective coefficient (K1 ). The tubing density may be calculated by the equation:

AP DT_GL = - x KI g x H

The system may not use the tubing density itself but a tubing density variation for the gas lock detection. If the MF regulator is in its tolerance zone during a sampling period (e.g. 60s), the criteria for Gaslock detection upon density variation may be,

wherein AP is the change in pressure for, t is time and dGL is a relative variation threshold for Gas lock detection.

Additionally or alternatively, conditions for determining a pocket gas lock type may include the processor monitoring a pump discharge pressure of the ESP. Detecting a gas lock by monitoring the pump discharge pressure may enable detecting a gas lock of a pocket type. The condition may be fulfilled if the pump discharge pressure system reaches at least one fifth predetermined threshold over a period of time lower than at least one fourth predetermined period of time. Like the second predetermined period of time and the third predetermined period of time, the fourth predetermined period of time may be a sliding interval. The at least one fifth predetermined threshold may correspond to a change (e.g. a decrease) in discharge pressure lying from 3% to 12% of the initial discharge pressure, for example from 5% to 10% of the initial discharge pressure. In other words, the at least one fifth predetermined threshold may be equal to the difference between an initial discharge pressure value and a certain percentage of the initial discharge pressure value (e.g. lying from 3 to 12% of the initial discharge pressure value). The initial t discharge pressure value may be a baseline value of discharge pressure, or a nominal value of discharge pressure. The at least one fourth predetermined period of time may be greater than or equal to 60 s and/or less than or equal to 60 s, for example between 30 s and 90 s. For example, taking a discharge pressure reference of 2600 psi, if in less that 1 min the discharge pressure comes from 2600 to 2340 psi, the system may determine a pocket gas lock type. For all conditions, the ESP frequency may meanwhile remain stable. This may be so as to ensure that the frequency is not causing the periodical oscillations. The processor may calculate a variation in the motor current and/or tubing density and/or pump discharge pressure for a predefined period of time, for example, every 60 seconds. If the motor frequency regulator is in its tolerance zone during the predefined period of time and the following equation is respected:

(Xt₊₆os-Xt) / Xt < dGL, wherein Xt is the MC or PDP or density value at the beginning of the 60s sampling period, X t+60s is the MC or PDP or density value at the end of the 60s sampling period and dGL is a stability criterion expressed as a percentage..

For gas locks determined to be of the pocket gas lock type, to manage the gas lock, the production target may be set to/ selected as (e.g. by an operator) motor frequency (MF) (if not already selected as such and MF is still desired) or wellhead temperature (WHT) (if not already selected as such and WHT is still desired). The processor may be further configured to execute a number of steps to manage the gas lock. The program may comprise instructions for the processor to then execute a gas lock frequency fallback phase. This may include continuing the regulation while also modifying certain production target values. When the system detects the pocket gas lock, it may send an alarm to the operator, for example via the GUI and/or via a default signal “gas lock detected” twinkle. The processor may send a message to the operator (e.g. via the GUI) to ask the operator if they would like to enter a manual mode. The managing may comprise the processor saving a pump frequency value on the memory. The managing may comprise the processor reducing the motor frequency value to a motor frequency setpoint value (MF set point). The motor frequency setpoint value may be equal to a gas lock motor frequency value (RCV_GL) with gas lock motor frequency ramp down (MF_RD_GL) speed. The managing may comprise the processor ramping down a choke value (e.g. an RCV) setpoint value to a gas lock choke setpoint value (e.g. gas lock RCV setpoint value). The managing may comprise the processor adjusting a pressure control valve (PCV) to maintain casing head pressure (CHP) regulation (PCV set point = CHP_Target). The managing may comprise the processor launching a timer (GL_D) when both the frequency and choke meet their respective positions.

After detection of a pocket type gas lock, the processor may execute a boosted ramp up sequence. This sequence may evacuate the gas slug quickly by performing an unusually fast ramp-up on the motor frequency. Adjusting production may comprise adjusting a controllable parameter (e.g. MF) value of the production well to meet a new target parameter value (e.g. MF or WHT). The managing may comprise the processor instructing the motor frequency to accelerate to a certain speed more quickly than it may normally increase the motor frequency. The processor may save a motor frequency value to the memory and may apply a motor frequency boost (dMF_Boost) with a motor frequency boost ramp up speed (MF_Boost_RU). In other words, the managing may comprise the processor increasing the motor frequency setpoint value to a motor frequency higher (MF+dMF_Boost) than the saved motor frequency value so as to evacuate the gas lock. The choke (e.g. RCV) may maintain a setpoint (e.g. RCV setpoint) to be equal to a choke gas lock value (e.g. an RCV gas lock value, RCV_GL). The PCV may maintain a CHP regulation (PCV set point = CHP_Target). Once the pump reaches the higher motor frequency (MF+dMF_Boost) setpoint, or once the gas lock is evacuated, the system may require an operator acknowledgement before continuing the regulation.

The processor may send a message (e.g. via the GUI) to inform the operator the type of the gas lock detected. The system may comprise an operator validation upon completion of the evacuating of the gas lock.

FIG. 2 displays an example of a well 750a and wellhead 750b equipped with an activation system 744 comprising ESP pump 700 connected above a separator 704, a protector 706, a transfer hydraulic line 736, and pump motor 708 placed above a downhole gauge 710. The downhole gauge 710 is connected to an acquisition module 716. The acquisition module 716 acquires data for calculation at the surface of gauge measurements including current leakage, voltage and imbalance, cable fault resistance, cable fault severity, and/or cable fault depth. These components of the activation system 744 are placed beneath a production packer 742. Downhole gauge measurements include ESP intake pressure (i.e. bottom hole pressure), ESP discharge pressure, ESP intake temperature (i.e. bottom hole temperature), motor winding temperature, vibration (X and Y axis), and/or tool head voltage. The pump motor 708 is connected to a variable speed drive (VSD) 718. The VSD 118 manages the motor frequency and motor current (back spin signal). The downhole gauge is connected to an acquisition module 716. The acquisition module 716 acquires data for calculation at the surface of gauge measurements including current leakage, voltage and imbalance, cable fault resistance, cable fault severity, and/or cable fault depth. Various valves are located along a liquid production line 746 for oil and water, the line 746 being connected to the pump 700 and including a DHSV 714, an ASV 712, a PMV 720, a production wing valve (PWV) 722, and an RCV valve 728. Sensors such as wellhead temperature sensor 724, wellhead pressure sensor 726, flow line temperature sensor 730b and flow line pressure sensor 730a are also located along the line 746 above the surface of the wellhead. A production gas line 748 is also connected to the wellhead 750b, along which various valves including an AMV valve 752, a PCV 738 and an AWV valve 740, along with sensors 732, 734. The sensors of the example of FIG. 2 may provide measurement information to the system for implementing the method. The processor may monitor activity anywhere along the ESP 744. For example, the pump may monitor activity at the pump 700, at the separator 704, and/or at the pump motor 708. The processor may execute the adjusting (e.g. reducing) by the RCV vale 728 along the liquid line 746. Additionally or alternatively, the processor may execute the adjusting by the PCV 738 to maintain a casing head pressure (CHP) regulation.

FIG. 3 presents an example of a schematic diagram illustrating an example of the system. The system implements a phase of production regulation 200 during which the system either detects a gas lock 202 (of a pocket type) or detects a gas lock 206 (of a continuous type). In this case, the detection of the gas lock 202 occurs by monitoring the motor current for a steady motor frequency. Additionally or alternatively, and regardless as to the production parameter selected, the detecting may occur through monitoring an ESP discharge pressure for a steady motor frequency. Additionally or alternatively, and regardless as to the production parameter selected, the detecting may occur by monitoring a tubing density (for, for example, a sudden decrease in tubing density) for a steady motor frequency. The system may determine the gas lock 202 to be of a pocket type (not shown in FIG. 3). Managing the gas lock 202, comprises selecting (e.g. by an operator) the target value to be other than BHP (if not already the case upon detection and determination). In other words, when the operator is launching the regulation system, they select a production target parameter to be a parameter other than BHP. The detection causes the processor to adjust an RCV gas lock (RCV_GL) setpoint with an RCV gas lock ramp down speed (RCV_RD_GL). Additionally, the detection causes the processor to adjust a motor frequency gas lock (MF_GL) setpoint with motor frequency gas lock ramp down speed (MF_RD_GL). Once a timer (GL_D) lapses, the processor implements a boosted ramp up function or sequence 204. The sequence comprises adding the last saved motor frequency value before the detection to a delta motor frequency boost value (A_MF_Boost). Meanwhile, an RCV setpoint value is maintained to an RCV gas lock value (RCV_GL). Once the system evacuates the gas lock 202 (of a pocket type), the processor may send a message (e.g. via a GUI) to ask the operator for a validation to return to normal production regulation 200, the settings returning to the same as those before the gas lock detection 202.

Detecting the continuous gas lock 206 occurs by monitoring the motor current for a steady motor frequency. Upon detecting the gas lock 206, the system may determine the gas lock 206 to be of a continuous type (not shown in FIG. 3). The detection causes the processor to launch a loop to protect the pump. The loop may be a part of the managing of the gas lock 206. The managing comprises selecting (e.g. by an operator) the target value to be BHP (if not already the case upon detection and determination). Firstly, the processor adjusts the WHP to be equal to WHP_Target+dP_WHP_GL x N, with N=1 for the first running of the loop. Upon reaching the “new” WHP value 208, the regulation of the BHP begins. The processor adjusts the BHP until its achieves a gas lock BHP target (GL_BHP_target), wherein the target is equal to [BHP_Target] + [dP_BHP_GL] x N, dP BHP GL, dP BHP GL (regulation starting with N=1 ). When the BHP achieves its target, i.e. when it reaches the “new” target 210, a timer (GL_D) runs to check motor current stability. If the motor current stability is ok, production regulation 200 can begin once again after the processor sends a message to the panel operator, which signals the operator to make any changes as necessary and asks for an operator acknowledgement. If, however, the processor detects a motor instability, the loop begins once again, this time for N=N+1 .

FIG. 4 provides an example of calculation of motor current instability for the continuous gas lock type. The graph displays motor current intensity as a function of time. In this example, the processor can detect the motor current instability when the absolute value of the when the absolute value of the difference between instantaneous and filtered measure becomes higher than the XXI_H threshold 300 more than three times in a 60 second sampling period 308. As can be seen from the figure, the raw motor current measure 306 fluctuates between upper threshold 300 and lower threshold 302, forming oscillations above and below filtered motor current measure 304 and reaching each respective threshold over a duration 308 of 60 seconds.

FIG. 5 provides an example of a GUI of the system. State 400 indicates that the system is implementing a production phase, while sub-state 402a indicates that the processor is implementing a gas lock fallback sequence. The GUI provides a timer 404 for the gas lock for this sequence. The GUI also comprises a deactivate button 412 and a FCW (full control well) stop button 410. In the case of the sub-state being a boosted ramp-up sequence 402b, the GUI presents a message 406 to the operator, “waiting gas lock ack”, for an acknowledgement from the operator. The operator can execute the acknowledgement by pressing the button 408.

FIG. 6 shows an example of the computer system, wherein the system is a workstation operable by a user. The computer system of the example comprises a central processing unit (CPU) 1010 connected to an internal communication BUS 1000, a random access memory (RAM) 1070 also connected to the BUS. The computer system is further provided with an optional graphical processing unit (GPU) 1110 which is associated with a video random access memory 1100 connected to the BUS. Video RAM 1100 is also known in the art as frame buffer. A mass storage device controller 1020 manages accesses to a mass memory device, such as hard drive 1030. Mass memory devices suitable for tangibly embodying computer program instructions and data include all forms of nonvolatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks. Any of the foregoing may be supplemented by, or incorporated in, specially designed ASICs (applicationspecific integrated circuits). A network adapter 1050 manages accesses to a network 1060. The computer system may also include a haptic device 1090 such as cursor control device, a keyboard or the like. A cursor control device is used in the computer system to permit the user to selectively position a cursor at any desired location on display 1080. In addition, the cursor control device allows the user to select various commands, and input control signals. The cursor control device includes a number of signal generation devices for input control signals to system. Typically, a cursor control device may be a mouse, the button of the mouse being used to generate the signals. Alternatively or additionally, the computer system may comprise a sensitive pad, and/or a sensitive screen.

FIG. 7 shows a graph displaying current intensity as a function of time, according to an example of the system. Time is displayed on the x-axis, and intensity / motor current is displayed on the y-axis in amperes (A). Reference “XXX A” refers to a baseline intensity (value) for fixed motor frequency 704 or baseline value for motor current 704 (e.g. 32A - which may for example correspond to an ESP intensity of 45 Hz). A threshold value “XXX-5% A” refers to a third predetermined threshold value 706. The intensity / motor current curve 702 is initially shown to stay at a value equal to that of the baseline intensity “XXX A”. The curve 702 then experiences a change or decrease in motor current, and reaches the threshold 706 over a period of time lower than a second predetermined period of time 708 that is equal to 1 minute. The second predetermined period of time 708 may be considered to be the first second predetermined period of time 708 of several second predetermined periods of time to capture the current curve 702 reaching the threshold 706. The ESP frequency may remain stable during the variation in current. As a result of the threshold conditions having been met, and for example by one or more other conditions of the system being met, the processor may determine a pocket gas lock type.

FIG. 8 shows an example of a graph displaying tubing density as a function of time, according to an example of the system. Time is displayed on the x-axis, and calculated tubing density is displayed on the y-axis in kg/m³. Reference “XXX kg/m3” refers to a baseline tubing density (value). A threshold value “XXX-5% kg/m3” refers to a fourth predetermined threshold value 806. A baseline tubing density curve 802 is initially shown to stay at a value equal to that of the baseline in tubing density “XXX kg/m3”. The curve 802 then experiences a change or decrease in tubing density, and reaches the threshold 806 over a period of time lower than a third predetermined period of time 808 that is equal to 1 minute. The third predetermined period of time 808 may be considered to be the first third predetermined period of time 808 of several third predetermined periods of time to capture the tubing density curve 802 reaching the threshold 806. As a result of the threshold conditions having been met, and for example by one or more other conditions of the system being met, the processor may determine a pocket gas lock type.

FIG. 9 shows an example of a graph displaying pump discharge pressure as a function of time, according to an example of the system. Time is displayed on the x-axis, and pump discharge pressure is displayed on the y- axis in Bar. Reference “XXX Bar” refers to a pump discharge pressure (value). A threshold value “XXX-5% Bar” refers to a fifth predetermined threshold value 906. A baseline pump discharge pressure curve 902 is initially shown to stay at a value equal to that of the baseline pump discharge pressure “XXX kg/m3”. The curve 902 then experiences a change or decrease in pump discharge pressure, and reaches the threshold 906 over a period of time lower than a fourth predetermined period of time 908 that is equal to 1 minute. The fourth predetermined period of time 908 may be considered to be the first fourth predetermined period of time 908 of several third predetermined periods of time to capture the pump discharge pressure curve 902 reaching the threshold 806. As a result of the threshold conditions having been met, and for example by one or more other conditions of the system being met, the processor may determine a pocket gas lock type.

Claims

1. A computer system for gas lock management in a hydrocarbon production well equipped with an artificial activation system, the artificial activation system comprising an electrical submersible pump (ESP) the system comprising:

- a processor coupled to the memory and configured to execute the program.

2. The system according to claim 1 , wherein the adjusting production comprises adjusting a controllable parameter value of the production well to meet a new target parameter value.

3. The system according to claim 1 or 2, wherein:

- the processor is configured to determine the continuous gas lock type when a motor current presents periodical oscillations, with ascending peaks being above a first predetermined threshold over a first predetermined period of time and/or descending peaks being below a second predetermined threshold over the first predetermined period of time, while the ESP frequency remains stable; and

- the processor is configured to determine the pocket gas lock type when the motor current reaches a third predetermined threshold over a period of time lower than a second predetermined period of time, while the ESP frequency remains stable, or when the motor current presents periodical oscillations with ascending peaks above a first predetermined threshold over a first predetermined period of time and/or descending peaks below a second predetermined threshold over the first predetermined period of time, while the ESP frequency remains stable.

4. The system according to any one of claim 3, wherein the periodical oscillations comprise from 2 to 10 peaks, for example 3 peaks, the first predetermined period of time ranging from 10 seconds to 2 minutes, for example, 60 seconds.

5. The system according to claim 3 or 4, wherein the first predetermined threshold is of the order of 2A, or of 3A, more than the initial current value, for example, the first predetermined threshold being equal to 2A, or 3A, more than the initial current value and the second predetermined threshold is of the order of 2A, or of 3A, less than the initial current value, for example, the second predetermined threshold being equal to 2A, or 3A, less than the initial current value.

6. The system according to any one of claims 3 to 5, wherein the at least one third predetermined threshold corresponds to a change in motor current lying from 0.5 to 20% of an initial motor current and the second predetermined period of time lies between 1 and 5 minutes or less than or equal to 30 seconds or greater than or equal to 30 seconds, for example the third predetermined threshold being 5% of the initial motor current and the second predetermined period of time being greater than or equal to 2 minutes, or for example the third predetermined threshold being 1 % of the initial motor current and the second predetermined period of time being greater than or equal to 24 seconds, or for example the third predetermined threshold lying from 10 to 15% of the initial motor current and the second predetermined period of time being greater than or equal to 15 seconds.

7. The system according to any one of claims 1 to 6, wherein the processor is further configured to monitor a tubing density, the determining of a pocket gas lock type occurring when the tubing density reaches at least one fourth predetermined threshold over a period of time lower than at least one third predetermined period of time.

8. The system according to claim 7, wherein the at least one fourth predetermined threshold corresponds to a change in tubing density lying from 3% to 12% of an initial tubing density, for example from 5% to 10% of an initial tubing density, and the at least one third predetermined period of time is greater than or equal to 1 min or less than or equal to 60 s, for example between 30 seconds and 90 seconds.

9. The system according to any one of claims 1 to 8, wherein the processor is further configured to monitor an ESP discharge pressure, the determining of a pocket gas lock type occurring when the pump discharge pressure system reaches at least one fifth predetermined threshold over a period of time lower than at least one fourth predetermined period of time.

10. The system according to claim 9, wherein the at least one fifth predetermined threshold corresponds to a change in discharge pressure lying from 3% to 12% of the initial discharge pressure, for example from 5% to 10% of the initial discharge pressure , and the at least one fourth predetermined period of time is greater than or equal to 60 s and/or less than or equal to 60 s, for example between 30 s and 90 s.

11. The system according to any one of claims 1 to 10, wherein the system further comprises an alarm configured to sound upon detection of the gas lock.

12. The system according to any one of claims 1 to 11 , wherein, for gas locks determined to be of the pocket gas lock type, to manage the gas lock, the production target is set to motor frequency (MF) or wellhead temperature (WHT) and the processor is further configured to:

- save a motor frequency value;

- reduce the motor frequency value to an motor frequency setpoint value;

- ramp down a choke opening setpoint value to a choke setpoint value;

- adjust a pressure control valve (PCV) to maintain a casing head pressure (CHP) regulation;

- launch a timer;

- increase the motor frequency setpoint value to a frequency higher than the saved motor frequency value so as to evacuate the gas lock.

13. The system according to any one of claims 1 to 12, wherein, for the adjusting production, the production target is set to bottom hole pressure (BHP) and the processor is configured to repeatedly: a) check if a choke opening value is greater than a choke heel value; b) confirm a new well head pressure target value is less than a maximum gas lock well head pressure; c) adjust the choke opening value to reach the well head pressure target value; d) upon reaching the well head pressure target value, adjusting the motor frequency to reach a bottom hole pressure target value; e) adjust the motor frequency to reach a new gas lock BHP target value; f) launch a timer; g) when the timer lapses, launch a check to see if the motor current is presenting periodical oscillations with ascending peaks above a first predetermined threshold over a first predetermined period of time and descending peaks below a second predetermined threshold over the first predetermined period of time; and h) if the oscillations are present, repeat steps a) to g).

14. The system according to any one of claims 1 to 13, wherein the processor is further configured to inform the operator of the type of the gas lock detected.

15. The system according to any one of claims 1 to 14, wherein the program is configured to receive an operator validation upon completion of the evacuation of the gas lock.

16. A computer program comprising instructions installable on a memory coupled to a processor so as to form a computer system for gas lock management according to any one of claims 1 to 15.

17. A data storage medium having recorded thereon a computer program according to claim 16.

18. A method for gas lock management in a hydrocarbon production well equipped with an artificial activation system, the artificial activation system comprising an electrical submersible pump (ESP), the method comprising:

- providing a computer system according to any one of claims 1 to 15; and

■ for gas locks determined to be of the pocket gas lock type, the managing comprises, temporarily increasing the ESP frequency to evacuate the gas locks, and

■ for gas locks determined to be of the continuous gas lock type, the managing comprises, adjusting production so as to reduce risks of damaging the ESP.