RU2697208C1 - Method for automatic maintenance of density of unstable gas condensate supplied to main condensate line, using turboexpander unit, in installations of low-temperature gas separation in areas of extreme north - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to the field of production and preparation of gas and gas condensate for long-distance transport. Proposed method comprises purification of incoming gas-condensate mix coming from production wells from mechanical admixtures in separator of first stage of separation. At the plant gas-condensate mixture is divided into UGC, gas and aqueous solution of inhibitor (ASI), with subsequent removal UGC and ASI into separator of liquids for degassing. From separator of liquids ASI is withdrawn for regeneration of inhibitor in inhibitor regeneration shop, and UGC pump is fed into manifold condensate line (MCL). Weathering gas from liquid separator is sent for use for own needs, for compression with subsequent pumping into main gas line or for recycling. To control density UGC APCS monitoring density sensor density UGC, supplied to MCL. Simultaneously APCS temperature sensor controls the temperature of the gas at the outlet of the low-temperature separator, the value of which is automatically maintained by controlling the rotational speed of the turbine expander (TDA), which is set by cascade of two proportional-integral-differentiating (PID) of regulators implemented based on APCS plant. To this end, the SP input PID-density maintenance regulator UGC at fluid separator output density setting signal is transmitted UGC, which value is set by maintenance personnel. And to feedback input PV of same PID-controller transmits actual density signal UGC from sensor installed at fluid separator outlet. Comparing said signals, PID-regulator generates at its output CV a rotor rpm setting signal TDA, providing required cooling of gas-liquid mixture supplied to input of low-temperature separator, and ensuring achievement of required density UGC at fluid separator outlet. Setpoint signal APCS sends SP input to input PID-rotor speed control regulator TDA. Simultaneously, to feedback input PV of this PID-regulator, from rotor rpm sensor TDA, rotor actual rpm signal is supplied TDA. Comparing input signals, PID-rotor speed control device TDA generates at its output CV control signal of control valve installed at output from turbine TDA. Due to this, control over the volume of dried gas leaving the low-temperature separator and passing through the compressor TDA. At that, APCS simultaneously controls and pressure in separator of liquids, automatically maintaining its value specified by process procedure of installation, by means of control valve installed at gas outlet from separator of liquids.

EFFECT: disclosed method enables automatic monitoring and maintaining a given density UGC, supplied to MCL, prevent formation of gas plugs and their accumulations in condensate line, reduced risk of occurrence of emergencies during operation MCL, associated with density fluctuations UGC.

1 cl, 2 dwg

Description

The invention relates to the field of production and preparation of gas and gas condensate for long-distance transport in the Far North, in particular, to automatically maintain the installation of low-temperature gas separation (hereinafter installation) the density of unstable gas condensate (NGC) supplied to the main condensate pipeline (MCP).

A known method of automating a low-temperature gas separation installation, including automatically maintaining the separation temperature, gas flow and pressure at the installation. [See, for example, p. 112, B.F. Taranenko, V.T. Hermann. Automatic control of gas production facilities. M., "Nedra", 1976, 213 pp.],

The disadvantage of this method is that it does not provide for controlling the degree of degassing and, accordingly, maintaining the density of NGCs when it is fed to the MCP. And this can cause a number of problems associated with the appearance of gas plugs and their accumulations in the condensate line. The presence of such traffic jams can cause serious complications and accidents leading to material, human and environmental losses. [Cm. e.g. A.A. Korshak, A.I. Zabaznov, V.V. Novoselov et al. Pipeline transport of unstable gas condensate. - M .: VNIIOENG, 1994.].

Closest to the technical nature of the claimed invention is a method of automating a low-temperature gas separation installation, including automatically maintaining the set temperature and pressure values at the installation. [See, for example, p. 406, R. Ya. Isakovich, V.I. Loginov, V.E. Come on. Automation of production processes in the oil and gas industry. Textbook for high schools, M., Nedra, 1983, 424 p.]. The degree of degassing of the OGC in this method is maintained by heating it using a coil-heater installed in the tank of the degasser-separator.

A significant drawback of this method is that due to the inertia of the heating process and the lack of control of the density of the OGC supplied to the MCP, the degree of degassing and maintaining the density of the OGC when it is supplied to the MCP is carried out practically “blindly” without precise process control.

The problem to which the present invention is directed, is to automatically maintain the density of the OGC supplied to the MCP, taking into account the norms and restrictions provided for by the technological regulations of the installation for the conditions of the Far North.

The technical results achieved from the implementation of the invention is the automatic maintenance of the density of gas condensate in the framework of the norms and restrictions provided by the technological regulations of the installation for various modes of its operation. The inventive method provides control and maintenance of a given density of OGC supplied to the MCP in order to prevent the formation of gas plugs and their accumulations in the condensate line. This increases the reliability of the operation of the MCP and reduces the likelihood of risks of complications and accidents that can lead to serious environmental, human and material losses.

This problem is solved, and the technical result is achieved due to the fact that the method of automatically maintaining the density of OGC supplied to the MCP using a turboexpander unit (TDA), at low-temperature gas separation units in the Far North, involves cleaning mechanical gas condensate mixture into the unit impurities and its separation into NGC, gas and an aqueous solution of an inhibitor (ARI), followed by removal of NGC and ARI to a liquid separator for degassing. From the liquid separator, BPI is diverted to the regeneration of the inhibitor in the inhibitor regeneration workshop, and the OGC is pumped to the MCP. Gas - the weathering gas from the liquid separator is sent for use for own needs, for compression with subsequent injection into the main gas pipeline (IHL), or for disposal.

To achieve this goal, the density sensor controls the density of the OGC supplied to the MCP. At the same time, the temperature sensor controls the gas temperature at the outlet of the low-temperature separator, the value of which is automatically maintained by controlling the rotational speed of the TDA rotor, which is set by a cascade of two proportional-integral-differentiating (PID) controllers implemented on the basis of an automated process control system (ACS TP) of the installation .

To do this, at the input of the job SP of the PID regulator for maintaining the density of OGCs at the output of the liquid separator, a signal of the OGC density setting is supplied, the value of which is set by the maintenance personnel. And at the feedback input PV of the same PID controller, a signal of the actual density of the OGC is supplied from the sensor installed at the output of the liquid separator. Comparing these signals, the PID controller generates at its output CV a signal for setting the rotational speed of the TDA rotor, which provides the necessary cooling of the gas-liquid mixture supplied to the inlet of the low-temperature separator, and ensures that the required density of OGCs is reached at the output of the liquid separator. The signal of this setting of the automatic process control system supplies the TDA rotor speed control PID controller SP input. At the same time, the feedback signal PV of this PID controller from the rotor speed sensor TDA is fed with a signal of the actual rotor speed TDA. Comparing the signals arriving at its inputs, the TDA rotor speed control controller TDA generates at its output CV a control valve control signal installed at the turbine outlet of the TDA. Due to this, the volume of dried gas leaving the low-temperature separator and pumped through the TDA compressor is controlled. At the same time, the automatic process control system simultaneously controls the pressure in the liquid separator, automatically maintaining its set value with the help of a control valve mounted on the gas outlet from the liquid separator.

In the process of solving the problem of maintaining a given density of OGCs, the temperature in the low-temperature separator can reach its limit values - upper or lower. Their values are indicated in the technological regulations of the installation. Also, the working body of the control valve controlling the volume of dried gas leaving the low-temperature separator and pumped through the TDA compressor can reach its extreme position - closed or open. In all these cases, the automatic process control system generates a message to the operator about the impossibility of achieving the specified density of the OGC supplied to the IHL, and the need to make a decision on changing the operating mode of the installation.

In FIG. 1 shows a schematic flow diagram of the installation and it uses the following notation:

1 - input line installation;

2 - separator of the first stage of separation;

3 - automated process control system;

4 - recuperative heat exchanger "gas-gas";

5 - recuperative gas-condensate heat exchanger;

6 - pressure sensor installed in the liquid separator;

7 - liquid separator;

8 - pressure control valve;

9 - density density sensor installed at the output of the liquid separator 7;

10 - pump unit;

11 - INC;

12 - low temperature separator;

13 - temperature sensor installed in the low temperature separator 12;

14 - TDA;

15 - sensor rotor speed TDA;

16 - IHL;

17- gas flow control valve;

In FIG. Figure 2 shows the block diagram of the automatic control of maintaining density at the installation and the following notation is used in it:

18 - signal from the sensor 15 of the rotor speed TDA 14, fed to the feedback input PV of the PID controller 22;

19 - signal from the density sensor 9 OGC, fed to the feedback input PV of the PID controller 21;

20 is a signal for setting the density of the OGC supplied to the MCP 11, received at the input of the reference SP of the PID controller 21;

21 - PID controller to maintain the density of NGC supplied to the MCP 11;

22 - PID controller for maintaining the rotor speed TDA 14;

23 is a control signal supplied to the gas flow control valve 17.

The method of automatically maintaining the density of OGC supplied to the MCP using TDA in low-temperature gas separation plants in the Far North is implemented as follows.

The gas-liquid mixture through the inlet line 1 is fed to the inlet of the separator of the first separation stage 2, in which it is purified from mechanical impurities, the partial release of NGC and an aqueous solution of the inhibitor (ARI), which, as they accumulate in the lower part of the separator 2, are discharged into the liquid separator 7. The gas-liquid mixture partially purified from dropping moisture and formation fluid from the output of the separator of the first separation stage 2 is divided into two parts and fed to the inlets of the first sections of recuperative heat exchangers 4 "gas-gas" and 5 "gas-con Densat ”for pre-cooling. Next, from the outputs of the first sections of the heat exchangers 4 and 5, the gas-liquid mixture flows are combined and fed to the inlet of the TDA 14 turbine, where the temperature of the gas-liquid mixture decreases as a result of adiabatic expansion. The impeller of the turbine TDA 14 is connected by a shaft to the impeller of the compressor and is equipped with a speed sensor 15. The required temperature in the low-temperature separator 12 is automatically maintained by changing the cooling capacity of the TDA 14 achieved by controlling the speed of its rotor. The rotor speed is controlled by controlling the degree of gas expansion in the TDA using the gas flow control valve 17 installed at the outlet of the TDA compressor 14. From the outlet of the TDA 14 turbine, the cooled mixture is fed to a low temperature separator 12 equipped with a temperature sensor 13. The final separator gas separation from NGK and VRI. Dried and cooled gas from the outlet of the low-temperature separator 12 through the second section of the recuperative heat exchanger 4 "gas-gas" is fed to the inlet of the compressor TDA 14. From the output of the compressor TDA 14, gas is supplied through the control valve 17 to the IHL and then to the consumer. NGK and ARI, as they accumulate in the lower part of the separator 12, are discharged through the second section of the recuperative gas-condensate heat exchanger 5 to the liquid separator 7, equipped with a pressure sensor 6. The mixture of NGK and VRI entering the liquid separator 7 from the separators is subjected to separation and degassing . The flow of released gas (weathered gas) from the liquid separator 7 is diverted through a pressure control valve 8 for use for own needs, for compression for supply to IHL 16 or for disposal. VRI sent for regeneration. OGC is diverted through a pipeline equipped with a density sensor 9 to the inlet of the pump unit 10 and further transportation through the MCP 11 to consumers.

The density of the OGC supplied to the MCP 11 is automatically maintained by changing the degree of extraction of the light fractions of the OGC from the gas-liquid mixture in the low-temperature separator 12. This is achieved by adjusting the temperature in it, realized by changing the cooling capacity of the TDA 14, controlled by the speed of its rotor.

To do this, the density value of the OGC supplied to the MCP 11 is set by the maintenance personnel in the form of a set point - signal 20, which is fed to the input of the SP job of the PID controller 21 to maintain the density of the OGC in the MCP. The feedback PV input of this PID controller is supplied with the value of the actual density of the OGC from the density measurement sensor 9. As a result of their processing, the PID controller 21 generates a value of the rotor speed setting TDA 14, which must be maintained, at its output CV. This setting is applied to the input of the SP task of the PID controller 22 for maintaining the rotational speed of the TDA rotor 14, and to the feedback input PV of the same PID controller, a signal 18 of the rotational speed of the TDA rotor is supplied from the sensor 15. As a result of the processing of the input signals, the PID controller 22 at its output CV, a signal 23 will be generated to control the degree of opening / closing of the valve-regulator 17, thereby controlling the rotational speed of the TDA rotor 14, and, therefore, the temperature in the separator 12.

In the case when the current value of the density of the OGC exceeds the value of the setpoint, the PID controller 21 maintain the density of the OGC increases the speed setpoint for the PID controller 22 to maintain the rotor speed of the TDA 14. As a result, the PID controller 22 generates a corresponding control signal 23 , which is supplied to the actuator of the valve-regulator 17. The valve will open slightly, which will lead to an increase in the rotational speed of the TDA rotor 14, and, accordingly, the temperature in the low-temperature separator 12 will decrease. And this will lead to an increase in the release of "light" fractions from the gas-liquid mixture, and the density of NGCs will decrease. In the case when the density should be increased, the operation will occur in the opposite direction.

There are cases when the working body of the valve-regulator 17 reaches its extreme position (closed or open), or the temperature in the low-temperature separator 12, controlled by the sensor 13, reaches the limit values (upper or lower) indicated in the technological regulations of the installation. In these cases, the automated process control system 3 of the installation generates a message to the operator about the impossibility of achieving the specified density of the OGC in the MCP and recommends a decision to change the operating mode of the installation.

In addition, the automatic process control system 3 supports in real time the pressure value determined by the operating procedure of the installation and the set value for the liquid separator 7 set by the maintenance personnel. To do this, it monitors its current value, the signal of which comes from pressure sensor 6, and controls it by changing degree of opening КР 8. Due to this, the required pressure is maintained in the liquid separator 7 in order to prevent the formation of vacuum and maintain the required level of condensate.

These PID controllers are configured by the operating personnel at the time the system is put into operation under specific production conditions according to the method described, for example, in the Encyclopedia of ACS TP, clause 5.5, PID controller. Resource: http://www.bookasutp.ru/Chapter5_5.aspx#HandTuning.

The method of automatically maintaining the density of NGC supplied to the MCP using TDA in low-temperature gas separation plants in the Far North was implemented in Gazprom PJSC Gazprom dobycha Yamburg at the Zapolyarnoye gas condensate field at complex gas treatment plants 1B and 2B.

The implementation of the method is most effective at a time when the reservoir energy of the field is no longer enough to operate the field using the Joule-Thompson throttling effect and additional energy is required to separate condensate from the gas-liquid mixture.

The operating results showed its high efficiency. The claimed invention can be widely used in other existing and newly developed gas condensate fields of the Far North of the Russian Federation.

The application of this method allows you to automatically control and maintain the given density of the OGC supplied to the MCP in order to prevent the formation of gas plugs and their accumulations, which makes it possible to increase the reliability of the operation of the condensate pipeline and reduce the likelihood of complications and accidents that could lead to serious environmental, human and material losses.

Claims (2)

1. A method for automatically maintaining the density of unstable gas condensate — OGC supplied to the main condensate line — MCP using a turboexpander unit — TDA, at low-temperature gas separation units in the Far North, including cleaning the incoming gas-condensate mixture into the installation from mechanical impurities and separating it into NGC, gas and an aqueous solution of the inhibitor - ARI, the removal of NGC and ARI to the liquid separator for degassing, and then the inhibitor from the liquid separator is diverted to regeneration and in the inhibitor regeneration workshop, and the OGC is pumped to the main condensate line - MCP, and the weathering gas from the liquid separator is sent for personal use, for compression for supply to the MHP or for utilization, characterized in that the density of the OGC supplied by the density sensor is monitored in the MCP and the temperature sensor, the gas temperature in the low-temperature separator, the value of which is automatically maintained by controlling the rotational speed of the TDA rotor, which is set by a cascade of two proportions ion-integral-differentiating - PID controllers, implemented on the basis of an automated process control system - automatic process control system, for which the input of the SP PID regulator for maintaining the density of gas condensate at the output of the liquid separator provides a signal for the density setting value set by the maintenance personnel, and the feedback signal PV of the same PID controller provides a signal of the actual density of the OGC from the sensor installed at the output of the liquid separator, comparing these signals, the PID controller generates at its output CV a signal for setting the rotational speed of the TDA rotor, which provides the necessary cooling of the gas-liquid mixture supplied to the input of the low-temperature separator, and ensures that the required density of the OGC is reached at the output of the liquid separator, and feeds it to the input of the SP PID controller for controlling the speed of rotation of the TDA rotor and its feedback input PV receives a signal of the actual rotational speed of the TDA rotor, comparing which, the PID controller generates a control signal for the valve regulator, controlling the volume of dried gas leaving the low-temperature separator and pumped through the TDA compressor, while the automatic process control system simultaneously controls the pressure in the liquid separator, automatically maintaining its set value using the control valve installed at the gas outlet from the liquid separator. 2. The method according to p. 1, characterized in that if, during the implementation of the process of maintaining a given density of OGCs, the temperature in the low-temperature separator reaches its limit values - upper or lower, indicated in the technological procedure of the installation, or the working body of the control valve that controls the volume of dried gas leaving the low-temperature separator and pumped through the TDA compressor will reach its extreme position - closed or open, then the automatic process control system generates a message to the operator about zmozhnosti achieve the desired density NGK supplied to the MCP, and the need for the decision to change the mode of operation.

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