RU2783036C1 - Method for automatic maintenance of temperature condition at low-temperature gas separation installations with turbo-expander units in the extreme north of the russian federation - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to the field of production and preparation of gas and gas condensate for long-distance transport. A method for automatically maintaining the temperature regime at low-temperature gas separation units with turbo-expander units (TEU) in the Far North of the Russian Federation includes preliminary cleaning of the produced gas condensate mixture from mechanical impurities with partial separation of the mixture of unstable gas condensate (UGC) and an aqueous solution of inhibitor (ASI) in the first stage separator separation, which is diverted from the cubic part of the separator to the liquid separator (LS), and the gas condensate mixture leaving the separator of the first separation stage is divided into two streams and fed for pre-cooling to the inlet of the first sections of the recuperative heat exchangers (HE) "gas-gas" and "gas-condensate". The gas condensate mixture is distributed among the streams using a control valve (CV) installed at the inlet of the HE "gas-condensate" so as to maintain the specified temperature of the UGC supplied to the main condensate pipeline (MCP). After passing through the first HE sections, both flows of the gas condensate mixture are combined and fed to the inlet of the TEU turbine, the rotation of which is controlled by the TEU rotor speed sensor, and the gas condensate mixture, passing through the turbine, is cooled and enters a low-temperature separator equipped with a temperature sensor, in which it is separated into dried cold gas and a mixture of UGC and ASI, which is fed from the bottom part of the low-temperature separator to the inlet of the second section of the HE "gas-condensate" and then to the LS, where it is degassed and separated into fractions, and then from the LS of the UGC is fed by a pump unit to the MCP , weathering gas is sent for disposal and/or compressed and sent to the main gas pipeline (MGP), ASI is sent to the inhibitor regeneration shop. The cold dry gas leaving the low-temperature separator is divided into two streams, one of which is fed to the inlet of the second section of the gas-to-gas HE, and the second to the bypass of this section, equipped with a gas flow control valve, and this control valve changes the ratio of gas flows through HE and bypass, providing real-time correction of the temperature of the gas entering the TEU compressor, which pressurizes the gas to the operating pressure and the set temperature, after which it is fed to the MGP. From the moment the unit is put into operation, the automated process control system (APCS) maintains a given flow rate of oil and gas supplied to the MCP, using for this the set values ​​of the settings of the controlled parameters and the limits of permissible deviations of their values ​​from the settings. As soon as the automated process control system detects that one of the controlled parameters goes beyond the limits set for it, violating the technological regulations for the operation of the installation, the automated process control system changes the value of the pressure set point P_in by one step. produced gas condensate mixture at the inlet of the installation by the value ΔP_in. in the interval determined by the inequality P_min≤P_in.≤P_max, where P_min is the minimum and P_max is the maximum value of the gas condensate mixture pressure setpoint at the unit inlet. The value of ΔP_in are assigned from the ratio ΔP_in=(P_max - P_min)/n, where n is the number of allowed steps for changing the P_in setting, and this change in the setting of the APCS is carried out in the direction that allows to eliminate the violation that has occurred. At the same time, the automated process control system monitors that the working body of the CV, which controls the pressure at the inlet of the installation, is within the allowable limits of its movement, and keeps the control mode of the technological processes of the installation with a new setpoint value for a time interval of at least τ_const, which is an individual characteristic of the installation determined experimentally. If the other controlled parameters of the technological process during this time return within the limits set for them, then the process control system fixes this value in its database (DB) as a new pressure setting for the produced gas condensate mixture at the inlet to the installation to maintain the flow of oil and gas supplied to the MCP, and generates a message to the operator about the automatic change of the operating mode of the installation and its new characteristics, and then the process control system implements this operating mode of the installation. Otherwise, the APCS changes the setpoint value by one more step in the same direction.

EFFECT: increasing the reliability of operation of the installation and the efficiency of the process of preparing gas and gas condensate for long-distance transport.

3 cl, 2 dwg

Description

The invention relates to the field of production and treatment of gas and gas condensate for long-distance transport, in particular, to automatic maintenance of the temperature regime of technological processes of a low-temperature gas separation unit (hereinafter referred to as the plant), using turbo-expander units (TDA) operating in the conditions of the Far North of the Russian Federation.

A known method of automating the installation of low-temperature gas separation [see, for example, page 406, R.Ya. Isakovich, V.I. Loginov, V.E. Popadko. Automation of production processes in the oil and gas industry. Textbook for universities, M., Nedra, 1983, 424 pp.], which maintains the separation temperature at the installation using a control valve (KR), which changes the flow of cold gas discharged from the low-temperature separator through a heat exchanger.

The disadvantage of this method is that maintaining the temperature regime at the plant is controlled by the flow rate of gas passing through the heat exchanger, which causes fluctuations in the temperature of the gas supplied to the main gas pipeline (MGP). There is also no control and maintenance of the required temperature of dried gas and unstable gas condensate (OGC), supplied respectively to the MGP and the main condensate pipeline (MCP) in order to protect permafrost soils from thawing during underground pipeline laying in the Far North [see, for example, p. 33-34, Ananenkov A.G., Stavkin G.P., Andreev O.P., Arabsky A.K., Salikhov Z.S., Talybov E.G. Automatic process control system for gas production facilities. - M.: Nedra-Businesscenter LLC, 2003. - 343 p.: ill.; page 19; Dmitriev V.M., Ganja T.V. and others. Intellectualization of control of technological processes in hydrocarbon deposits. Tomsk: V-Spectrum, 2012. - 212 p.].

A known method of automating the installation of low-temperature gas separation [see, for example, p. 112, B.F. Taranenko, V.T. Hermann. Automatic control of gas production facilities. M., "Nedra", 1976, 213 pp.], which automatically maintains the setpoint of the separation temperature at the installation by maintaining the necessary pressure drop at the regulator fitting installed at the inlet to the low-temperature separator, by correcting the pressure at the outlet of the first stage separation plant.

The disadvantage of this method is that the maintenance of the temperature regime at the plant is carried out by regulating the pressure drop across the reducing valve installed at the inlet to the low-temperature separator of the plant. This, in turn, imposes restrictions on the inlet pressure and gas flow through the installation, and it also does not provide for control and maintenance of the required temperature of the dried gas and oil and gas supplied to the MGP and MCP, respectively, in order to protect permafrost soils from thawing during underground laying pipelines in the Far North [see. for example, pp. 33-34, Ananenkov A.G., Stavkin G.P., Andreev O.P., Arabsky A.K., Salikhov Z.S., Talybov E.G. Automatic process control system for gas production facilities. - M.: Nedra-Businesscenter LLC, 2003. - 343 p.: ill.; p. 19, Dmitriev V.M., Ganja T.V. and others. Intellectualization of control of technological processes in hydrocarbon deposits. Tomsk: V-Spectrum, 2012. - 212 p.].

The closest in technical essence to the claimed invention is a method for automatically maintaining the temperature regime of technological processes using TDA at a low-temperature gas separation unit in the Far North [see. patent of the Russian Federation No. 2680532], which includes preliminary purification of the extracted gas condensate mixture from mechanical impurities with partial separation of the mixture of NGK and an aqueous solution of inhibitor (ARI) in the separator of the first separation stage. This mixture of NGK and VRI is discharged from the bottom part of the separator into a liquid separator (RJ). The gas condensate mixture from the outlet of the separator of the first separation stage is cooled by adiabatic expansion in the TDA and fed into the low-temperature separator of the second separation stage, where it is finally separated into dry cold gas and a mixture of oil and gas with VRI. This mixture of NGK with VRI is also taken to the RJ, where it is degassed and separated into fractions.

At the same time, the gas condensate mixture coming from the separator outlet of the first separation stage is divided into two streams and fed for pre-cooling to the inlet of the first sections of recuperative heat exchangers, then gas-gas HT and gas-condensate HT. The distribution of the gas condensate mixture by streams is carried out with the help of the KR installed at the inlet of the TO "gas-condensate". This CR regulates the flow rate of the gas condensate mixture through the HT "gas-condensate", ensuring that the specified temperature of the mixture of OGK and VRI is maintained at the outlet of the second section of the HT "gas-condensate". After passing through the first TO sections, both flows of the gas condensate mixture are combined and fed to the TDA turbine inlet.

The turbine rotation speed is controlled by the TDA rotor speed sensor. The cooled gas condensate mixture leaving the TDA is fed into a low-temperature separator equipped with a temperature sensor, in which it is separated into dried cold gas and a mixture of NGK and VRI. The cold mixture of NGK and VRI from the bottom part of the low-temperature separator is fed to the inlet of the second section of the TO "gas-condensate" and then to the RJ, where it is degassed and separated into fractions. From RJ OGK, a pump unit is fed into the MCP, the weathering gas (HW) is sent for disposal and/or compressed with subsequent supply to the MGP, and the VRI is sent to the inhibitor regeneration shop.

The cold dried gas leaving the low-temperature separator is divided into two streams, one of which is fed to the inlet of the second section of the gas-gas TO, and the second to the bypass of this section, equipped with a gas flow control valve. This KP changes the ratio of gas flows through the TO and bypass, providing real-time correction of the temperature of the gas entering the TDA compressor. In the TDA compressor, the gas is compressed to the operating pressure and temperature required to supply it to the MGP.

A significant disadvantage of this method is that in cases where the temperature of the dried gas/NGK entering/supplying to the MGP/MKP, as well as in the low-temperature separator, reaches its limit values - upper or lower, indicated in the technological schedule of the installation, the change in the operating mode of the installation is carried out by the operator manually, which reduces the quality of process control.

The aim of the invention is to improve the quality of process control to maintain the temperature regime of the installation using TDA, operating in the conditions of the Far North of the Russian Federation, within the limits and restrictions provided for by the technological regulations of the installation, and to reduce the role of the human factor in the process control to maintain the temperature regime of the installation.

The technical result achieved from the implementation of the proposed method is to improve the quality of process control to maintain the temperature regime of the installation using TDA, operating in the conditions of the Far North of the Russian Federation. The human factor is also excluded when making managerial decisions to change the process control mode, taking into account the norms and restrictions provided for by its technological regulations. The result is:

- automatic maintenance of the set temperature regime of technological processes of the installation, necessary for its efficient operation;

- automatic control and maintenance of the required temperature of dry gas/NGK entering/supplying to MGP/MKP in order to protect permafrost pounds from defrosting during underground laying of gas pipelines in the Far North of the Russian Federation.

The efficiency of a low-temperature gas separation plant is determined by the value of the pressure drop between its inlet and outlet - the higher the pressure drop, the easier it is to obtain a given (minus) temperature in the low-temperature separator of the plant by throttling. It is obvious that at the stage of the life cycle of fields with increasing gas production, characterized by its high pressure at the inlet of the installation, the set operating mode can be maintained due to reservoir pressure (reservoir energy). At the stages of the life cycle of fields with constant and declining gas production, and there are currently quite a lot of such in the Far North of the Russian Federation, the pressure drop between the inlet and outlet of the installation drops due to a decrease in reservoir pressure. In this case, it is possible to ensure the specified temperature regime in the low-temperature separator of the installation by attracting an additional source of cold. In the natural and climatic conditions of the Far North of the Russian Federation, where there are stable colds for up to eight months, air coolers are used as an additional source of cold in winter. During the warm months of operation of the plant, from late spring to autumn, their use becomes impossible. During this period, the TDA plays the role of an additional source of cold for the installation.

Also, an undesirable change in the pressure drop between the inlet and outlet of the installation can occur at any stage of field operation when the gas flow rate changes due to fluctuations in gas consumption by consumers, in case of violation of the normal operation of the well stock, etc. There are also periods of high ambient temperature during the summer period of operation of the unit, which can reach up to 32°C. All this directly affects the temperature regime of operation of the low-temperature separator, for the leveling of which it is necessary to control the operation of the plant, taking into account changes in the current pressure drop and all the above factors. Accordingly, it is necessary to correct the temperature of the gas condensate mixture entering the low-temperature separator, ensuring its required operating values, which is implemented by controlling the temperature of the gas condensate mixture at the outlet of the TDA turbine.

In the case of underground laying of MGP and MCP, and in the Far North this particular method of laying MGP and MCP is used, year-round cooling of gas and gas condensate to a temperature not higher than -2°C is provided to prevent thawing of permafrost subsiding soils around MGP and MCP. Due to this, the reliability of operation of main gas and condensate pipelines is significantly increased and the likelihood of emergency situations that can lead to serious environmental, human and material losses is reduced.

Installations located in the Far North of the Russian Federation, depending on the current situation with the supply of produced products to consumers, implement one of three possible types of their operation:

1. Supports the flow rate of the produced gas condensate mixture through the installation, if there are no peak loads for dry gas or oil and gas.

2. Maintains dry gas flow through the plant during peak dry gas loads, such as the onset of severe cold weather in winter, or the surge in dry gas volumes required for pumping into underground storage facilities in summer.

3. Maintains OGK consumption for the installation when there are peak loads on OGK, for example, due to accidents at other fields or due to the need to increase supplies to the consumer.

The inventive method provides automatic control and maintenance of a given temperature regime at low-temperature gas separation plants with TDA, operating in the conditions of the Far North of the Russian Federation and implementing the third type of operation, which provides for maintaining a given flow rate of oil and gas supplied to the MCP. The method also includes maintaining the required temperature values of the dried gas/NGK entering/supplying to the MGP/MKP, as well as the temperature in the low-temperature separator with automatic switching of the technological process to a new operating mode in case of such a need. This increases the reliability of operation of the plant and the efficiency of the process of preparing gas and gas condensate for long-distance transport.

The specified problem is solved, and the technical result is achieved due to the fact that the method of automatically maintaining the temperature regime at low-temperature gas separation plants with TDA in the Far North of the Russian Federation includes preliminary cleaning of the produced gas condensate mixture from mechanical impurities with partial separation of the mixture of OGK and VRI in the first stage separator separation, which is diverted from the cubic part of the separator into the RJ. The gas condensate mixture leaving the separator of the first separation stage is divided into two streams and fed for pre-cooling to the inlet of the first sections of the gas-to-gas HT and the gas-condensate HT. This gas condensate mixture is distributed among the streams by means of a CR installed at the inlet of the TO "gas-condensate" so as to ensure that the specified temperature of the OGK supplied to the MCP is maintained. After passing through the first TO sections, both flows of the gas condensate mixture are combined and fed to the inlet of the TDA turbine, the rotation of which is controlled by the TDA rotor speed sensor. The gas condensate mixture passing through the turbine is cooled as a result of adiabatic expansion and enters a low-temperature separator equipped with a temperature sensor. In this separator, the final separation of the gas condensate mixture into dried cold gas and a mixture of OGK and VRI, which is fed from the bottom part of the low-temperature separator to the inlet of the second section of the gas-condensate TO and further to the RJ. In the RJ, degassing and separation into fractions of the incoming mixture takes place. Further, from the RJ NGK is pumped to the MCP, the GW is sent for disposal and/or compressed and sent to the MGP, and the VRI is sent to the inhibitor regeneration shop.

The cold dried gas leaving the low-temperature separator is divided into two streams, one of which is fed to the inlet of the second section of the gas-gas TO, and the second to the bypass of this section, equipped with a gas flow control valve. This CR changes the ratio of gas flows through the TO and bypass, providing real-time correction of the temperature of the gas entering the TDA compressor, which pressurizes the gas to the operating pressure and the set temperature, after which it is fed to the MGP.

From the moment the plant is put into operation, the automated process control system (APCS) maintains the specified flow rate of oil and gas supplied to the MCP. To do this, the automated process control system uses the specified values of the settings of controlled parameters and the limits of permissible deviations of the values of these parameters from their settings. And as soon as the APCS detects the output of one of the controlled parameters beyond the limits set for it, which violates the technological regulations for the operation of the installation, the APCS changes the value of the pressure setpoint P in by one step _. produced gas condensate mixture at the inlet of the installation by the value of ΔР _in. Changing this setting is allowed in the interval determined by the inequality P _min ≤Р _in. ≤P _max , where P _min is the minimum allowable, and P _max is the maximum allowable value of the gas condensate mixture pressure setpoint at the unit inlet. The value of ΔР _in. appoint from the ratio of ΔR _in. =(P _max - P _min )/n, where n is the number of allowed steps for changing the setpoint P _in. . Setpoint change P _in. The automated process control system carries out in the direction that allows to eliminate the violation that has occurred, and at the same time, the automated process control system simultaneously monitors that the working body of the CR, which controls the pressure at the inlet of the installation, is within the allowable limits of its movement. By changing the setpoint value by one step, the automated process control system maintains the process control mode of the plant with a new setpoint value for a time interval of at least τ _const , which is an individual characteristic of the plant, determined experimentally. And if all other controlled parameters of the technological process during this time return within the limits set for them, then the process control system fixes this value in its database (DB) as a new pressure setting for the produced gas condensate mixture at the inlet to the installation to maintain the flow of oil and gas supplied to MCP. At the same time, the APCS generates a message to the operator about the automatic change of the plant operation mode and its new characteristics, and then the APCS implements this mode of operation of the plant. Otherwise, the APCS changes the setpoint value one more step in the same direction.

Before the plant is put into operation, the operating personnel enters the value of Rin into the APCS database _. - pressure setting at the inlet to the installation, and the boundaries of the interval of its allowable changes from P _min to P _max . Also enter the value of the setpoint of the OGK flow rate supplied to the MCP input, and the limits of the interval of permissible deviations of the actual flow rate Q of the OGK OGK from its set point, given by the inequality Q _{min ≤Q} OGK _{≤Q max} , where Q _min is the minimum allowable value, and Q _max - the maximum allowable value of the OGK flow rate supplied to the MCP.

The value of the temperature setpoint in the low-temperature separator and the boundaries of the interval of permissible deviations of the actual temperature T°C _HC from it are entered, given by the inequality T°C _{min_HC} ≤T°C _HC ≤T°C _{max_HC} , where T°C _{min_HC} is the minimum allowable value, and T °C _{max_HC} - the maximum allowable temperature value in the low-temperature separator.

Enter the temperature setpoint for the oil and gas condensate entering the _MCP and the boundaries of the interval of permissible deviations of the _{actual temperature} T°C of _{the oil} and gas _complex from it, given by the inequality and T°C _{max_NGK} - the maximum allowable temperature value of the NGK supplied to the MCP.

The setpoint for the temperature of the dried gas supplied to the _MGP and the boundaries of the interval of permissible deviations of the actual _temperature T°C of the _{exhaust gas from} it are _entered , given by the inequality , and T°C _{max_OG} - the maximum allowable temperature of the dried gas supplied to the MGP.

The boundaries of permissible displacements S _{CR 2} of the working body CR that maintains the pressure of the produced gas condensate mixture at the inlet of the installation are set from the minimum allowable open position S _{min_CR 2} to fully open.

The boundaries of the maximum allowable movement S _{CR 5} of the working body CR installed at the outlet of the first stage separator and supporting the flow of dried gas supplied to the MGP are set from the minimum allowable open position S _{min_CR 5} to fully open.

The boundaries of the maximum allowable movement S _{KR 12} of the working body KR, which controls the rotation speed of the TDA rotor and installed at the outlet of the TDA compressor, are set from the minimum allowable open position S _{min_KR 12} to fully open.

After entering the specified data into the database of the process control system, the installation is put into operation, and all technological processes in it are carried out by the process control system. To do this, it uses four PID controllers and one cascade of two PID controllers built on its basis. Each of these four PID controllers, with the help of the KR connected to them, controls its own parameter.

The cascade of two PID controllers works as follows. The first PID controller, comparing the actual temperature in the low-temperature separator with its setpoint, generates a signal of the operational value of the setpoint of the rotational speed of the TDA rotor, necessary to maintain the temperature required by the technological regulations in the low-temperature separator, and feeds it to the input of the second PID controller of the cascade. The second PID controller, comparing the actual speed of rotation of the TDA rotor with the operational setting of its rotation speed, generates a control signal for the RC connected to it, which sets the required speed of rotation of the TDA rotor.

The automated process control system generates a message to the operator of the installation to make a decision on changing the operation mode of the clusters of gas producing wells, if in the mode of changing the setpoint P _in. using KR installed at the inlet of the installation and controlling the pressure of the produced gas condensate mixture at its inlet, it will be revealed that its working body has switched to the fully open state or has reached the minimum allowable open position S _{min_kr 2} , or the setpoint P _in. went beyond one of the boundaries of its permissible changes.

In FIG. 1 shows a schematic flow diagram of a low-temperature gas separation unit used in the Far North of the Russian Federation and the following designations are used in it:

1 - input line of the installation;

2 - KR maintaining the pressure of the gas condensate mixture at the inlet of the installation;

3 - pressure sensor of the produced gas condensate mixture at the inlet of the installation;

4 - separator of the first stage of separation;

5 - KR of the flow of oil and gas supplied to the MGP;

6 - KR flow rate of the gas condensate mixture passing through TO "gas-condensate" 10;

7 - automated process control system of the installation;

8 - TO "gas-gas";

9 - KR flow of dried gas through the bypass of the second section of TO "gas-gas";

10 - TO "gas-condensate";

11 - RJ;

12 - KR for controlling the speed of rotation of the TDA rotor;

13 - dry gas temperature sensor entering the MGP;

14-TDA;

15 - TDA rotor speed sensor;

16 - temperature sensor in the low-temperature separator 17;

17 - low-temperature separator;

18 - flow sensor of NGK supplied to the MCP;

19 - temperature sensor of NGK supplied to the MCP;

20 - pump unit.

In FIG. Figure 2 shows a block diagram of the automatic temperature control of the installation. It uses the following notation:

21 - pressure signal of the gas condensate mixture at the inlet of the installation, coming from the sensor 3;

22 - signal of the pressure setting of the gas condensate mixture at the inlet of the installation;

23 - temperature signal of the dried gas supplied to the MGP, coming from the temperature sensor 13;

24 - signal for setting the temperature of the dry gas supplied to the MGP;

25 - temperature signal of the oil and gas complex supplied to the MGP, coming from the temperature sensor 19;

26 - temperature setpoint signal of the oil and gas complex supplied to the MCP;

27 - signal of the consumption of oil and gas supplied to the MCP, coming from the sensor 18;

28 - signal of the setpoint of the flow rate of the oil and gas complex supplied to the MGP;

29 - signal of the speed of rotation of the rotor TDA 15 coming from the sensor 15;

30 - temperature signal in the low-temperature separator 17 coming from the temperature sensor 16;

31 - temperature setpoint signal in the low-temperature separator 17;

32 - PID controller for maintaining the pressure of the produced gas condensate mixture at the inlet of the installation;

33 - PID controller for maintaining the temperature of the dried gas supplied to the MGP;

34 - PID controller for maintaining the temperature of the OGK supplied to the MGP;

35 - PID controller for maintaining the flow of oil and gas supplied to the MCP;

36 - PID controller, which generates the operational value of the setpoint of the rotation speed of the TDA rotor, necessary to maintain the set temperature in the low-temperature separator 17;

37 - PID controller for maintaining the speed of rotation of the rotor TDA 14;

38 - control signal KR 2;

39 - control signal KR 9;

40 - control signal KR 6;

41 - control signal KR 5;

42 - control signal KR 12.

PID controllers 32, 33, 34, 35, 36 and 37 are implemented on the basis of APCS 7.

A method for automatically maintaining the temperature regime at installations for low-temperature gas separation with TDA in the Far North of the Russian Federation is implemented as follows.

The produced gas condensate mixture through the inlet line 1 of the unit equipped with a pressure sensor 3 and KR 2 enters the inlet of the separator of the first stage of separation 4, in which the gas condensate mixture is initially purified from mechanical impurities, partial separation of NGK and VRI, the mixture of which, as it accumulates in the lower part of the separator 4 is discharged to the RJ 11. The gas condensate mixture, partially purified from condensate moisture and reservoir fluid, from the outlet of the separator of the first stage of separation 4 passes through the CR 5, which regulates the flow rate of the gas condensate mixture through the installation so that the flow rate of OGK supplied to the MCP does not went beyond the limits of permissible deviations relative to the setpoint set by the dispatching service of the Enterprise. The gas condensate mixture leaving the CR 5 is divided into two streams and fed to the inlets of the first sections TO 8 "gas-gas" and TO 10 "gas-condensate" for pre-cooling. At the same time, the gas condensate mixture enters the TO 10 “gas-condensate” inlet through the CR 6, which is used by the process control system to maintain the required temperature of the OGK supplied to the MCP. Further, the flows of the gas condensate mixture from the outlets of the first sections TO 8 "gas-gas" and TO 10 "gas-condensate" are combined and fed to the inlet of the turbine TDA 14. Passing the impeller of the turbine TDA 14, the gas condensate mixture expands adiabatically, as a result of which its temperature drops to value close to that provided for by the technological regime of the low-temperature separator. The resulting deviation of the actual temperature from the value provided for by the technological regulations of the installation for the low-temperature separator 17 APCS compensates in real time by changing the speed of rotation of the rotor TDA 14 by controlling the flow of dried gas through its compressor, using for this purpose KR 12 installed at the outlet of TDA 14.

From the outlet of the TDA 14 turbine, the cooled gas condensate mixture is fed into the low-temperature separator 17, equipped with a temperature sensor 16. In the separator, the final separation of gas from the NGK and VRI takes place, the mixture of which, as it accumulates in the lower part of the separator 17, is removed through the second section TO 10 " gas-condensate" in RJ 11. The dried and cooled gas from the outlet of the low-temperature separator 17 is divided into two streams, one of which is fed into the second section of TO 8 "gas-gas", and the second is sent to the bypass of this section. The bypass is equipped with KR 9, with the help of which the APCS controls the flow rate of the cooled gas passing through it, coming from the low-temperature separator 17, thus regulating the temperature of the gas entering the TDA 14 compressor inlet. Thanks to this, the APCS maintains the specified temperature of the compressed gas coming from the outlet compressor TDA 14 in MGP.

The mixture of NGK and VRI discharged into RJ 11 from separators 4 and 17 is subjected to separation into components and degassing. The flow of the released gas (GV) from the RJ 11 is sent for disposal or compressed and fed to the MGP. NGK is discharged using pump unit 20 to the MCP and transported to consumers, and the WRI flow is sent for regeneration to the plant inhibitor regeneration shop.

The implementation of this method solves the following problems: a) Automatic maintenance of the pressure of the gas condensate mixture at the inlet of the installation. To do this, ACS TP 7 uses a PID controller 32, to the feedback input PV of which it sends a signal 21 - the value of the actual pressure at the inlet of the installation, measured by sensor 3 installed at the inlet to separator 4. At the same time, ACS TP 7 to the input of the task SP of the same PID -regulator gives a signal 22 - the value of the pressure set point P _in. at the input of the installation. As a result of their processing, the PID controller 32 generates a signal 38 at its output CV, which controls the degree of opening / closing of the CR 2, which ensures that the pressure at the inlet of the installation is practically equal to the setpoint P _in. .

b) Maintaining the set temperature of the dried gas supplied to the MGP. Its automated process control system solves by controlling the flow of gas passing through the second section TO 8 "gas-gas". To do this, part of the flow of cold dry gas discharged from the low-temperature separator 18 is directed through the bypass of this section, on which the KR 9 is installed. To do this, the automated process control system 7 to the feedback input PV of the PID controller 33 sends a signal 23 - the temperature of the dried gas Tmgp entering the MGP, the value of which is measured using a temperature sensor 13 installed at the inlet to the MGP. At the same time, a signal 24 is sent to the input of the task SP of the PID controller 33 of the automated process control system 7 - the temperature setting of the dried gas entering the MGP. As a result of processing these signals at the CV output, the PID controller 33 generates a control signal 39 for the KP 9. If the temperature in the MHP should be increased/lowered, the amount of cold gas passing through the bypass will be reduced/increased. As a result, the temperature of the dried gas entering the MGP will correspond to the temperature specified by the technological regulations of the plant.

c) Maintaining the set temperature of the OGK supplied to the MCP. Its automated process control system solves by managing with the help of KR 6 the flow rate of the gas condensate mixture passing through the first section TO 10 "gas-condensate". The task to change the position of the working body KR 6 forms the PID controller 34. For this, the automated process control system 7 sends a signal 25 to the _feedback input PV of the PID controller 34 - the value of the temperature at the entrance to the MCP. At the same time, ACS TP 7 sends a signal 26 to the input of the SP task of this PID controller - the setpoint for the temperature of the oil and gas complex, which must be maintained at the outlet of the installation (at the input of the MCP). As a result of processing these signals, the PID controller 34 generates at its output CV a control signal 40 for KR 6. If the temperature in the MCP should be increased / decreased, the amount of gas condensate mixture passing through the first section of the TO 10 "gas-condensate" will be increased \\ reduced. Accordingly, the temperature of the OGK entering the MCP will correspond to the set technological regulations of the installation.

d) Automatic maintenance of the specified flow of oil and gas supplied to the MCP. To do this, ACS TP 7 uses a PID controller 35, to the feedback input PV of which a signal 27 is applied - the value of the actual flow rate of oil and gas supplied to the MCP, measured using sensor 18 installed at the inlet to the MCP. At the same time, ACS TP 7 sends a signal 28 to the input of the task SP of the PID controller 35 - the setpoint of the flow of oil and gas supplied to the MCP. Its value is set by the dispatching service of the gas producing enterprise. Comparing these signals, the PID controller 35 at its output CV generates a signal 41, which controls the degree of opening/closing of the CR 5, maintaining the flow rate of the OGK supplied to the MCP set by the task.

e) Automatic maintenance of the set temperature of the gas condensate mixture entering the low-temperature separator 17 from the outlet of the TDA 14 turbine. Its automated process control system solves it by controlling the rotation speed of the TDA 14 rotor, changing the flow rate of dried cold gas through its compressor using the KR 12 installed at the outlet of the TDA 14 .

The rotation speed of the TDA 14 rotor is controlled by the PID controller 37. To do this, the process control system 7 sends a signal 29 to the input of its feedback PV - the current value of the rotation speed V of the _TDA of the TDA 14 rotor, measured by sensor 15. the signal of the operational value of the setpoint V _{set_TDA} of the speed of rotation of the rotor of the TDA 14, which must be maintained at the moment so that the temperature in the low-temperature separator 17 corresponds to its setting. The operational value of the setpoint V _{set_TDA} forms the PID controller 36 at its output CV as a result of signal processing - the value of the actual temperature in the low-temperature separator, recorded by the sensor 16, and the temperature setpoint in it. The current value of this temperature is a signal 30, the process control system 7 sends it to the feedback input PV of the PID controller 36, and it sends the signal 31 of the temperature setpoint in the low-temperature separator to its input SP.

In the case when the temperature in the low-temperature separator 17 needs to be lowered, the CR 12 is slightly opened, and thereby the load on the TDA 14 compressor is reduced. at the inlet to the low-temperature separator 17. If it is necessary to increase the temperature in the low-temperature separator 17, the CR 12 is covered, which leads to a decrease in the speed of rotation of its rotor. As a result, the temperature of the gas condensate mixture at the outlet of the TDA 14 turbine, i.e. at the inlet to the low-temperature separator 17 rises.

Before the unit is put into operation, the maintenance personnel sets and enters into the APCS 7 database a number of necessary parameters, including settings, the limits of permissible deviations of the values of controlled parameters from their settings, as well as the limits of permissible movements of the working bodies of the CR.

Enter the setting P _in. - the pressure of the gas condensate mixture at the inlet of the installation and the limits of its permissible changes, which are set in the form of an inequality

where P _min is the minimum and P _max is the maximum value of the set pressure of the gas condensate mixture at the unit inlet. In this case, the change in the current value of the setpoint R _in. APCS 7 produces only if necessary and step by step, by the value of ΔР _in. , which is assigned from the ratio ΔR _in. =(P _max - P _min )/n, where n is the number of allowed steps for changing the setpoint P _in .

Simultaneously impose restrictions on the position of the working body CR 2, which can vary from fully open to covered up to a strictly specified, lower value S _{min_CR2} . The interval of its allowable movements is set in the form of the inequality S _{min_KP2} ≤S _KP2 , where S _KP2 is the current position of the working body of KP 2. As a result, the automated process control system 7 controls the step-by-step change of the setpoint P _in. pressure of the gas condensate mixture at the inlet of the installation using KR 2, simultaneously observing the requirements of a system of two inequalities

The set point for the flow rate of the oil and gas complex supplied to the MCP is entered, and the permissible deviations of the current value of its flow rate Q of the oil and _{gas complex} relative to the setpoint are set as an inequality

where Q _min is the minimum, and Q _max is the maximum value of the OGK flow rate supplied by the MCP.

Simultaneously impose restrictions on the position of the working body KR 5, which can vary from fully open to covered up to a strictly specified, lower value S _{min_KR5} . The interval of its allowable movements is set as the inequality S _{min_KR 5} ≤S _{KR 5} , where S _{KR 5} is the current position of the working body of KR 5.

Accordingly, APCS 7 manages the process of supplying oil and gas supplied to the MCP, taking into account the allowable deviations of the flow rate from the setpoint and restrictions on the operation of the CR 5, i.e. satisfies the requirement of simultaneous compliance with the system of two inequalities

The setpoint for the temperature of the dried gas entering the MGP is entered, and the limits of permissible deviations of its current temperature T°C of the _{exhaust gas} relative to the setpoint are set in the form of the inequality

where T°C _{min_OG} is the minimum allowable, and T°C _{max_OG} is the maximum allowable dry gas temperature.

The temperature setting for the oil and gas complex entering the MCP is entered, and the boundaries of permissible deviations of its current temperature Т°С of the oil and _{gas complex} relative to the set point are given by the inequality

where T°C _{min_NGK} is the minimum allowable temperature, and T°C _{max_NGK} is the maximum allowable value of the NGK temperature.

The temperature setpoint is entered in the low-temperature separator, and the boundaries of permissible deviations of its current value Т°С _НС relative to the setpoint are set by the inequality

where, T°C _{min_HC} - the minimum allowable, and T°C _{max_HC} - the maximum allowable temperature in the low-temperature separator.

The boundaries of permissible changes in the rotor speed V _TDA TDA 14 are set in the form of an inequality

where V _min is the minimum allowable rotation speed, and V _max is the maximum allowable rotation speed of the TDA rotor.

At the same time limit the position of the working body KP 12, which can vary from fully open to covered to a strictly specified, lower value S _{min_KP 12} . The interval of its allowable movements is set as the inequality S _{min_KR 12} ≤S _{KR 12} , where S _{KR 12} is the current position of the working body of KR 12.

Accordingly, APCS 7 manages the operation of the TDA, taking into account this condition and restrictions on the operation of KR 12, i.e. satisfies the requirement of simultaneous compliance with the system of two inequalities

During the operation of the installation, the position of the working bodies of KR 6 and KR 9, in contrast to the position of KR 2, KR 5 and KR 12, can vary from fully open to fully closed.

Before putting the unit into operation, the service personnel also enters into the DB APCS 7 the initial values of the degree of opening of KR 2, KR 5, KR 6, KR 9 and KR 12.

When the unit is put into operation, ACS TP 7 in real time monitors the position of the working bodies of KR 2, KR 5, KR 6, KR 9 and KR 12, as well as the flow of oil and gas supplied to the MGP using a flow sensor 18, temperature in the low-temperature separator 17 using sensor 16, the temperature of the dried gas/NGK entering/supplied to MGP/MCP using sensors 13 and 19, respectively.

By controlling the specified parameters, the APCS 7 manages the technological process, taking into account the above restrictions and maintains stable fulfillment of the task for the consumption of oil and gas - the basic (main) mode. If in the course of operation it is not possible to achieve the specified flow of oil and gas supplied to the MCP, or the specified temperature in the low-temperature separator 17, or the specified temperature of the dried gas / oil and gas entering / supplied to the MGP / MCP, or the rotation speed of the rotor V _TDA will go beyond the permissible limits, or the working body of KR 5 or KR 6 or KR 9 or KR 12 will move to one of its extreme positions, then ACS TP 7 automatically switches the unit to the next mode of operation. This transition provides for changing the pressure setting of the gas condensate mixture at the inlet of the installation P _in. one step within the limits of the changes allowed for it. This transition to a new mode of APCS 7 implements with the help of PID controller 32 and controlled by him KR 2 within the limits set by the system of inequalities (1), changing the value of the initial setpoint P _in. one step. At the same time, ACS TP 7 generates a message to the operator of the installation about the automatic transfer of the installation to the next mode of operation.

This mode of APCS 7 implements by increasing/decreasing the value of the setpoint P _in. , depending on the situation in one direction or another, up to the value

The APCS 7 sends this new setpoint value in the form of a signal 22 to the input SP of the PID controller 32. By comparing its value with the actual pressure at the inlet of the plant coming from sensor 3, the PID controller 32 generates a control signal 38 at its output CV and sets the corresponding value degree of opening/closing of CR 2. This leads to a change in the pressure of the produced gas condensate mixture at the inlet to the unit, which causes a change in the pressure drop across the turbine TDA 14. Due to this, an increase/decrease in temperature in the low-temperature separator 17 will occur, which, in turn, will lead to to eliminate the deviation that has arisen - an increase / decrease in the flow rate of dried gas entering the MGP or the temperature of the gas / oil and gas entering the MGP / MCP.

Correction of the setpoint value of the pressure at the inlet of the installation P _in. APCS 7 performs step by step, depending on the direction of the violation and taking into account the inertia of the technological processes of the installation. The number of steps n, covering the entire interval of allowable changes in the pressure setpoint at the inlet of the installation P _in. , as a rule, is assigned equal to 10, 5 steps in each direction from the originally set value. At the same time, at each step, the APCS 7 implements the process control mode of the installation with a new setpoint value for a time interval of at least τ _const , which is an individual characteristic of the installation, determined experimentally. In particular, for the installations of the Zapolyarnoye oil and gas condensate field, time τ _const is required to complete transient processes of the order of 10 minutes. If, during the implementation of the first or next step, it is possible to eliminate the violation that occurred during the technological process - to restore the specified flow rate of dried gas entering the MGP, or the specified temperature in the low-temperature separator 17, or the specified temperature of the dried gas/NGK entering/supplied to the MGP/MCP, either to return the working body of KR 5 or KR 6 or KR 9 or KR 12 to its operating range of positions, or to return the speed of rotation of the TDA rotor to the operating range, then APCS 7 continues to work with this new setpoint value, fixing its value in its database in as a task. Otherwise, ACS TP 7 will continue the search by changing the value of the setting P _in. one more step.

This mode of correction of the setpoint P _in. with the help of KR 2 allows APCS 7 to repeatedly return to previously implemented modes of operation, including the original one.

If in the correction mode of the setpoint P _in. with the help of KR 2, one of the limits of its permissible changes, P _max or P _min , will be reached, or the working body of KR 2 will go into the fully open state or S _{min_KR2} , but the flow rate of the OGK supplied to the MCP, or the temperature of the dried gas / OGK entering / supplied to the MGP / MCP, or the temperature in the low-temperature separator will not fall within the specified limits, APCS 7 generates a message about this to the plant operator to make a decision on changing the operating mode of the gas well clusters.

The adjustment of the PID controllers used is carried out by the maintenance personnel at the time the system is put into operation for a specific mode of operation of the installation according to the method described, for example, in the Encyclopedia of Process Control Systems, clause 5.5, PID controller, resource:

http://www.bookasutp.ru/Chapter5_5.aspx#HandTuning.

The method for automatic maintenance of the temperature regime at low-temperature gas separation units with TDA in the Far North of the Russian Federation was implemented in PJSC Gazprom, LLC Gazprom dobycha Yamburg at the Zapolyarnoye oil and gas condensate field at GTP 1 V and GTP 2 V. The results of operation showed its high efficiency. The claimed invention can be widely used in other existing and newly developed gas condensate fields located in the regions of the Extreme Russian Federation. The use of this method allows you to automatically maintain the temperature regime at the installations within the framework of technological standards and restrictions provided for by their technological regulations, which makes it possible to:

- automatically keep within the established limits the course of technological processes of the installation, ensuring its efficient operation, taking into account the dynamics of the current values of external and internal parameters;

- control and maintain the specified flow rate of oil and gas condensate entering the MCP, as well as the temperature of the dried gas/oil and gas entering/supplying to the MGP/MCP, in order to protect permafrost soils from thawing during underground laying of gas and condensate pipelines in the Far North of the Russian Federation.

Claims (3)

1. A method for automatically maintaining the temperature regime at low-temperature gas separation units with turbo-expander units - TDA in the Far North of the Russian Federation, including preliminary purification of the produced gas condensate mixture from mechanical impurities with partial separation of a mixture of unstable gas condensate - NGK and an aqueous solution of inhibitor - VRI in the first stage separator separation, which is removed from the bottom part of the separator to the liquid separator - RJ, and the gas condensate mixture leaving the separator of the first separation stage is divided into two streams and fed for pre-cooling to the inlet of the first sections of recuperative heat exchangers, then TO, "gas-gas" and "gas-condensate", while the gas-condensate mixture is distributed by streams using a valve-regulator - KR, installed at the inlet of TO "gas-condensate", so as to ensure the maintenance of the specified temperature of the OGK supplied to the main condensate pipeline - MCP, and after passing the first sections of maintenance, both The current of the gas condensate mixture is combined and fed to the inlet of the TDA turbine, the rotation of which is controlled by the TDA rotor speed sensor, and the gas condensate mixture, passing through the turbine, is cooled and enters a low-temperature separator equipped with a temperature sensor, in which it is separated into dry cold gas and a mixture of oil and gas and VRI, which is fed from the bottom part of the low-temperature separator to the inlet of the second section of the TO "gas-condensate" and then to the RJ, where it is degassed and separated into fractions, and then from the RJ of the NGK is fed to the MCP by a pump unit, the weathering gas is sent for disposal and / or compressed and sent to the main gas pipeline - MGP, VRI is sent to the inhibitor regeneration shop, and the cold dried gas leaving the low-temperature separator is divided into two streams, one of which is fed to the inlet of the second section of the TO "gas-gas", and the second - to the bypass of this section, equipped with a gas flow RC, and this RC changes the ratio of gas flows through the TO and bypass, about providing real-time correction of the temperature of the gas entering the TDA compressor, which compresses the gas to the operating pressure and the set temperature, after which it is fed to the MGP, characterized in that the automated process control system - APCS from the moment the unit is put into operation maintains the specified flow rate of OGK supplied to the MCP, using for this purpose the set values of the settings of the controlled parameters and the limits of permissible deviations of their values from the settings, and as soon as the APCS detects the output of one of the controlled parameters beyond the limits set for it, violating the technological schedule of the installation, the APCS changes by one step the value of the set pressure P _in. produced gas condensate mixture at the inlet of the installation by the value of ΔР _in. in the interval determined by the inequality P _min ≤Р _in. ≤P _max , where P _min is the minimum, and P _max is the maximum value of the pressure setting of the gas condensate mixture at the inlet of the installation, and the value of ΔР _in. appoint from the ratio of ΔR _in. =(P _max - P _min )/n, where n is the number of allowed steps for changing the setpoint P _in. , and this change in the setting of the automated process control system is carried out in the direction that allows to eliminate the violation that has occurred, and at the same time the automated process control system ensures that the working body of the CR, which controls the pressure at the inlet of the installation, is within the allowable limits of its movement, and maintains the process control mode installation with a new setting value for a time interval of at least τ _const , which is an individual characteristic of the installation, determined experimentally, and if the remaining controlled parameters of the technological process during this time return within the limits established for them, then the process control system fixes in its database - DB this value as a new pressure setting for the produced gas condensate mixture at the inlet to the unit to maintain the flow of oil and gas supplied to the MCP, and generates a message to the operator about the automatic change in the operating mode of the unit and its new characteristics, and then the automated process control system implements this mode of operation of the unit, otherwise The process control system changes the setpoint one more step in the same direction. 2. The method according to p. 1, characterized in that before the installation is put into operation, the maintenance personnel enters the value of the pressure setpoint P _in. at the inlet to the installation and the limits of the interval of its allowable changes from P _min to P _max , enters the value of the setpoint of the flow rate of the oil and gas complex supplied to the MCP, and the boundaries of the interval of permissible deviations of the actual flow rate Q of the oil and gas complex of the oil and gas complex from it, given by the inequality Q _{min ≤Q} of the oil and gas complex _{≤Q max} , and also enters the temperature setpoint in the low-temperature separator and the boundaries of the interval of permissible deviations of the actual temperature T°С _HC from it, given by the inequality T°C _{min_HC} ≤T°C _HC ≤T°C _{max_HC} the boundaries of the interval of permissible deviations of the actual temperature Т°С of the _{oil and gas complex from it, specified by the inequality T°C min_NGK ≤Т} °С of the oil and gas condensate _≤T °C _{max_NGK} , enters the temperature setting for the dried gas supplied to the MGP, and the boundaries of the interval of permissible deviations of the actual temperature Т°С _EG from it, given by the inequality T°C _{min_OG} ≤T°C _OG ≤T°C _{max_OG} , and also sets the boundaries of movement S _{CR 2} of the working body of the CR that maintains the pressure of the produced gas condensate mixture at the inlet is set vki, from position S _{min_KP 2} - minimum open, to fully open, sets the boundaries of the maximum allowable movement S _{KP 5} of the working body of the KP, supporting the flow of dried gas supplied to the MGP, from position S _{min_KP 5} - minimum open, to fully open, sets the limits of the maximum allowable movement S _{KR 12} of the working body of the KR, which controls the rotation speed of the TDA rotor, from the position S _{min_KR 12} - minimally open to fully open, after which it launches the installation into operation, the technological processes in which are carried out by the automated process control system using four PID- controller and one cascade of two PID controllers built on its basis, and each of these four PID controllers, with the help of the KR connected to them, controls its parameter, and in the cascade of two PID controllers, the first one generates a signal of the operational value of the speed setpoint rotation of the TDA rotor, necessary to maintain the temperature required by the technological regulations in the low-temperature sep arator, and feeds it to the second PID controller of the cascade, which controls the speed of rotation of the TDA rotor with the help of the KR connected to it. 3. The method according to p. 2, characterized in that the automated process control system generates a message to the operator of the installation to make a decision on changing the operating mode of the clusters of gas producing wells, if in the mode of correcting the setpoint P _in. with the help of the KR installed at the inlet of the installation and controlling the pressure of the produced gas condensate mixture at its inlet, it will be revealed that its working body has switched to the fully open state or has reached the minimum open position S _{min_KR2} , or the setpoint P _in. went beyond the limits of its permissible changes.

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