RU2828195C1 - Method of preparing hydrocarbon gas for transportation - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to gas industry for field preparation for transportation of products of gas and gas condensate deposits. Method of preparing hydrocarbon gas for transportation involves separate supply of gas flow from gas wells and gas flow from gas condensate wells and their separate treatment. Gas flow from gas wells is supplied to primary separation for separation of water phase, which is removed from plant, and to adsorption dehydration, then dried gas is heated with compressed dried gas, compressed and cooled with air, cooled compressed dried gas is additionally compressed in compressor of turboexpander, successively cooled by heat exchange with air and with dried gas after adsorption drying, as well as by reducing the pressure in the expander of the turboexpander, after which the cooled dried gas is removed from the plant. Gas flow from gas condensate wells is supplied for separation of liquid phase for primary separation and for adsorption dehydration, dried gas is heated with compressed dried gas, then it is compressed and cooled with air, additionally compressed in the turboexpander compressor and successively cooled by heat exchange with air and with dried gas after adsorption drying, as well as by heat exchange with unstable condensate and stripped gas, cooled compressed dried gas is divided into two streams: first is separated from condensate and supplied to expander of turboexpander for cooling by pressure reduction and is directed for separation of unstable condensate from gas into low-temperature separator, and the second is fed into the ejector as an active flow and is combined with the first flow after the expander, stripped gas from the low-temperature separator is heated by compressed dried gas to a temperature of not more than 0 °C and output from installation, reducing the pressure of the liquid phase after the primary separation of the gas stream of the gas condensate wells and then directing it for separation from the unstable condensate of the water phase and the high-pressure degassing gas, which is introduced into the cooled gas before the low-temperature separator, aqueous phase is removed from the plant, the pressure of the unstable condensate is lowered and directed to separate the weathering gas and residual water, which is introduced into the aqueous phase and removed from the plant, reducing the pressure of the liquid hydrocarbon phase after the low-temperature separation and directing it to separate the low-pressure degassing gas from the unstable condensate, which is further heated by compressed dried gas of gas condensate wells and combined with unstable condensate separated from liquid phase after primary separation of gas flow of gas condensate wells, separated from weathering gas and residual water unstable condensate is removed from the plant, low-pressure degassing gas is directed to the ejector as a passive flow, the weathering gas is compressed and fed into the gas flow of gas condensate wells after primary separation.

EFFECT: integrated use of equipment for preparation of products of gas and gas condensate wells.

2 cl, 1 dwg

Description

The invention relates to the gas industry, in particular to the processing of hydrocarbon gas using adsorption and low-temperature processes, and can be used for industrial preparation for transport of products from gas and gas condensate fields.

A method for preparing hydrocarbon gas for transportation is known (patent for invention RU 2701020, IPC E21B 43/34, B01D 53/00, published: 09/24/2019), in which the gas flow from gas condensate well clusters is separated in three stages to separate the aqueous phase and unstable condensate, while the gas flow is cooled with air, unstable condensate, and separated gas, methanol is introduced before cooling the gas flow to prevent hydrate formation and the water-methanol solution is recirculated from the last separation stage after the primary separation, the unstable condensate is degassed, the aqueous phase is separated from it, the degassing gas of the unstable condensate is utilized, and the separated gas, unstable condensate, and water-methanol solution are removed from the unit. The disadvantage of the known method is its limited use without the possibility of using it for the simultaneous preparation of gas flows from two different horizons, from which "lean" gas and gas condensate reservoir fluid are extracted. In addition, methanol used as a hydrate formation inhibitor dissolves in unstable condensate, separation gas and aqueous solution, which leads to significant losses of the inhibitor during the preparation of gas and condensate.

The closest analogue to the proposed solution is a method for industrial preparation of gas condensate deposits (patent for invention RU 2615703, IPC B01D 19/00, F25J 3/06, published: 06.04.2017), in which the gas flow from the gas condensate well clusters enters the block of slug catchers and sequentially undergoes air cooling, additional separation, adsorption of the aqueous phase, division of the flow into two parts, cooling of one part of the flow with separated gas and the other part of the flow with unstable condensate, mixing of the gas flow, its separation from the condensate, cooling of the gas flow by reducing the pressure in the expander of the turboexpander, low-temperature separation of the gas flow from the condensate, heating of the separated gas in the dephlegmator with condensate deethanization gas from the low-temperature separator and the gas flow after adsorption, compression separated gas in the turboexpander compressor, additional compression and removal of separated gas from the unit, unstable condensate with an aqueous phase from the plug collector unit is sent to a separator tank for separating the aqueous phase, which is removed from the unit, after which the unstable condensate is fed to deethanization and removed from the unit, unstable condensate from the low-temperature separator is introduced into the unstable condensate from the separator and sent for low-temperature deethanization, after which it is removed from the unit, degassing gas and deethanization gas from the unstable condensate from the plug collector unit are mixed, compressed and introduced into the gas stream after cooling with air, low-temperature deethanization gas is cooled in a dephlegmator for separating propane, which is returned to deethanization, then the low-temperature deethanization gas is heated by the deethanized condensate, compressed and introduced into the separated gas. This method eliminates the need to use methanol in low-temperature gas processing, but has the following disadvantages:

- a limitation on the use of equipment used in the scheme for the simultaneous preparation of "lean" gas and gas condensate reservoir fluid from various development sites, given that as production from the gas condensate deposit decreases, the capacity of adsorption gas drying is released, which is effective for the preparation of "lean" gas from the gas deposit;

- positive gas temperature at the outlet of the installation, while when transporting gas in permafrost soil, it is necessary to ensure a negative gas temperature at the outlet of the installation.

The objective of the claimed invention is to eliminate the above-mentioned shortcomings, and the technical result consists in the integrated use of equipment for the preparation of gas (“lean” gases) and gas condensate well products.

The stated problem is solved and the technical result is achieved due to the fact that the method for preparing hydrocarbon gas for transportation includes feeding a gas flow from gas condensate well clusters and then to a block of plug collectors, adsorbing the aqueous phase from the gas flow, cooling the gas flow with air, low-temperature separation of the gas flow, while separately feeding the gas flow from the gas wells and the gas flow from the gas condensate wells and preparing them separately, the gas flow from the gas wells is first fed to the primary separation for separating the aqueous phase, which is removed from the unit, and to the adsorption drying, then the dried gas is heated with compressed dried gas, compressed and cooled with air, the cooled compressed dried gas is additionally compressed in the turbo expander compressor, sequentially cooled by heat exchange with air and with the dried gas after adsorption drying, as well as by reducing the pressure in the turbo expander expander, after which the cooled dried gas is removed from the installation, wherein the gas flow from the gas condensate wells is first fed for separating the liquid phase to the primary separation and to the adsorption drying, the dried gas is heated with the compressed dried gas, then it is compressed and cooled with air, additionally compressed in the turbo expander compressor and successively cooled by heat exchange with air and with the dried gas after the adsorption drying, as well as by heat exchange with the unstable condensate and the stripped gas, the cooled compressed dried gas is divided into two flows: the first (90% of the total volume of the flow being separated) is separated from the condensate and fed to the turbo expander expander for cooling by reducing the pressure and is directed to separate the unstable condensate from the gas in the low-temperature separator, and the second (10% of the total volume of the flow being separated) is fed to the ejector as an active flow for reducing the pressure and is combined with the first flow after the expander, the stripped gas from the low-temperature separator is heated with compressed dried gas to a temperature of no more than 0°C and removed from the unit, the pressure of the liquid phase is reduced after the primary separation of the gas flow of the gas condensate wells and then sent to separate the aqueous phase and high-pressure degassing gas from the unstable condensate, which is introduced into the cooled gas before the low-temperature separator, the aqueous phase is removed from the unit, the pressure of the unstable condensate is reduced and sent to separate the weathering gas and residual water, which is introduced into the aqueous phase and removed from the unit, the pressure of the liquid hydrocarbon phase is reduced after low-temperature separation and sent to separate the low-pressure degassing gas from the unstable condensate, which is then heated with compressed dried gas of the gas condensate wells and combined with the unstable condensate isolated from the liquid phase after the primary separation of the gas flow of the gas condensate wells, the unstable condensate separated from the weathering gas and residual water The condensate is removed from the unit, the low-pressure degassing gas is sent to the ejector as a passive flow, the flash gas is compressed and introduced into the gas flow of gas condensate wells after primary separation.

Unlike the prototype, equipment for primary separation, adsorption, primary heat exchange, compression and cooling of gas in air cooling devices is used to prepare gas from both gas deposits (“lean” gas) and gas condensate.

The claimed invention can be implemented on a corresponding installation for preparing hydrocarbon gas for transport, schematically shown in Fig. 1, using the following designations:

1 - pipeline;

2 - primary separator block;

3 - pipeline;

4 - adsorber block;

5 - pipeline;

6 - gas-to-gas heat exchanger unit;

7 - pipeline;

8 - compressor block;

9 - pipeline;

10 - air cooler block;

11 - pipeline;

12 - compressor;

13 - pipeline;

14 - air cooler block;

15, 16 - pipeline;

17 - expander;

18-28 - pipeline;

29 - gas-condensate heat exchanger;

30 - pipeline;

31 - gas-to-gas heat exchanger;

32 - pipeline;

33 - flow divider;

34 - control valve;

35 - pipeline;

36 - low-temperature separator;

37, 38 - pipeline;

39 - low-temperature separator;

40 - control valve;

41 - pipeline;

42 - reducing device (ejector);

43-46 - pipeline;

47 - reducing device (throttle);

48 - pipeline;

49 - three-phase separator;

50 - pipeline;

51 - reducing device (throttle);

52 - pipeline;

53 - three-phase separator;

54 - pipeline;

55 - reducing device (throttle);

56 - pipeline;

57 - two-phase separator;

58 - pipeline;

59 - reducing device (throttle);

60-62 - pipeline;

63 - reducing device (throttle);

64-70 - pipeline;

71 - compressor;

72 - pipeline;

73 - turboexpander unit block.

The hydrocarbon gas preparation unit for transportation operates as follows. The gas flow from the gas wells for removing the aqueous phase is successively fed through pipeline 1 to the primary separator unit 2 and through pipeline 3 to the adsorber unit 4. The dried gas is directed through pipeline 5 to the gas-to-gas heat exchanger unit 6, where it is heated, and then goes through pipeline 7 to the compressor unit 8 and through pipeline 9 to the air cooler unit 10. After cooling, the compressed dried gas is fed through pipeline 11 to compressor 12 of turboexpander unit 73 and then successively passes through pipeline 13 to the air cooler unit 14 and through pipeline 15 to the gas-to-gas heat exchanger unit 6 for heating the dried gas. The cooled gas enters the expander 17 of the turbo-expander unit 73 via pipeline 16 for cooling by reducing the pressure, and the prepared gas is removed from the unit via pipeline 18. The aqueous phase from the primary separator unit 2 is removed from the unit via pipeline 19.

The gas flow from the gas condensate wells is fed through pipeline 20 to the primary separator block 2 for separating the liquid aqueous and hydrocarbon phases and then through pipeline 21 to the adsorber block 4. The dried gas is sent through pipeline 22 to the gas-to-gas heat exchanger block 6 for heating and through pipeline 23 to the compressor block 8 for increasing the pressure. The compressed dried gas is fed through pipeline 24 to air cooler unit 10, through pipeline 25 to compressor 12 of turbo-expander unit 73 and then through pipeline 26 to air cooler unit 14. Partially cooled compressed dried gas for additional cooling passes sequentially through pipeline 27 to gas-gas heat exchanger unit 6, through pipeline 28 to gas-condensate heat exchanger 29 and through pipeline 30 to gas-gas heat exchanger 31. The cooled compressed dried gas is fed through pipeline 32 to flow divider 33, from where the main flow (90% of the total volume of the divided flow) is directed through control valve 34 through pipeline 35 to low-temperature separator 36, through pipeline 37 to expander 17 of turbo-expander unit 73 for cooling due to reducing the pressure and then through pipeline 38 into low-temperature separator 39 for separating the liquid hydrocarbon phase from the cooled dried gas. The second flow (10% of the total volume of the separated flow) from flow divider 33 through control valve 40 through pipeline 41 is directed as an active flow into ejector 42 and then through pipeline 43 is combined with the main flow entering through pipeline 38 into low-temperature separator 39. The stripped gas from low-temperature separator 39 is directed through pipeline 44 into gas-to-gas heat exchanger 31 for heating and then through pipeline 45 is removed from the plant. The liquid hydrocarbon phase from low-temperature separator 39 enters through pipeline 58 into reducing device 59 for reducing the pressure and then through pipeline 60 into two-phase separator 57 for separating the low-pressure degassing gas from the unstable condensate.

The liquid phase from the primary separator block 2 is fed via pipeline 46 to the reducing device 47 and then via pipeline 48 to the three-phase separator 49 for separation from the unstable condensate of the aqueous phase and high-pressure degassing gas. The unstable condensate from the three-phase separator 49 is directed via pipeline 50 to the reducing device 51 for lowering the pressure and then via pipeline 52 to the three-phase separator 53 for additional separation of residual water and flash gas.

Unstable condensate from two-phase separator 57 is fed through pipeline 61 to gas-condensate heat exchanger 29 for heating, through pipeline 62 it enters pressure-reducing device 63 for lowering pressure and then through pipeline 64 it is introduced into unstable condensate transported through pipeline 52 to three-phase separator 53. After separation of residual water and weathering gas from unstable condensate in three-phase separator 53, unstable condensate is removed from the plant through pipeline 65.

High-pressure degassing gas from three-phase separator 49 is introduced through pipeline 66 into pipeline 38 before low-temperature separator 39. Low-pressure degassing gas from two-phase separator 57 is fed through pipeline 67 as a passive flow into ejector 42. Ventilation gas from three-phase separator 53 is fed through pipeline 68 into compressor 71 and through pipeline 72 is introduced into pipeline 21 before adsorber unit 4.

The aqueous phase from the three-phase separator 49 is combined with the residual water from the three-phase separator 53, supplied via pipeline 70, and is discharged from the plant via pipeline 69.

Traditionally, the development of multi-layer deposits begins with the upper gas deposits, which contain "lean" gas, mainly consisting of methane. Such gas can be prepared by absorption or adsorption drying, or low-temperature separation. Subsequently, the underlying gas condensate deposits are brought into development, the formation fluid of which is prepared by low-temperature separation to obtain gas and condensate, while in order to exclude the use of methanol, water is first extracted from the gas using adsorption drying. Two gas preparation units are built to prepare "lean" and condensate-containing gas.

According to the claimed invention, the development of a multi-deposit field begins with gas condensate deposits, for which a gas preparation unit is built with a dedicated part of the process equipment, which can be used both for the preparation of "lean" gas and for the preparation of condensate-containing gas. At the first stage, gas condensate deposits are introduced into development.

Formation fluid from gas condensate deposits enters the primary separator block 2 to separate condensate and water phase from the gas flow. From the primary separator block 2, gas enters the adsorber block 4 to extract moisture and ensure the gas dew point temperature is below minus 40°C. The dried gas is then heated in the gas-to-gas heat exchanger block 6 to a temperature of 30-35°C and compressed in the compressor block 8 to a pressure of 8.2-8.5 MPa, after which it is cooled in the air cooler block 10 to a temperature of 25-30°C. Then the cooled gas is compressed in compressor 12 of turbo-expander unit 73 to a pressure of 10 MPa, cooled in air cooler unit 14 to a temperature of 25-30°C and first fed to gas-to-gas heat exchanger unit 6, where it is cooled to 27-32°C, and then to gas-to-condensate heat exchanger 29 for cooling to a temperature of 19-21°C. Next, the gas flow is cooled in gas-to-gas heat exchanger 31 to a temperature of minus 2°C and divided into two parts. The first part (90% of the total volume of the divided flow) is directed for separation to low-temperature separator 36 and fed to expander 17 of turbo-expander unit 73, in which the pressure is reduced to 5.6 MPa and the temperature to minus 31°C. The second part of the gas (10% of the total volume of the separated flow) enters as active gas into the reducing device (ejector) 42, where the pressure is reduced to 5.6 MPa and cooled to a temperature of minus 24°C. Then both gas flows are mixed, and the combined gas flow is directed to the low-temperature separator 39 to separate the unstable condensate from the gas, after which the separated gas is directed to the gas-to-gas heat exchanger 31, where it is heated to a temperature of minus 3 degrees and removed from the unit.

Liquid from the primary separator block 2 is fed to the reducing device (throttle) 47 to reduce the pressure to 6 MPa, after which it is sent to the three-phase separator 49. High-pressure degassing gas is mixed with the combined gas flow before the low-temperature separator 39, and the aqueous phase is removed from the unit. Unstable condensate from the three-phase separator 49 is sent to the reducing device (throttle) 51 to reduce the pressure to 3 MPa. Unstable condensate from low-temperature separator 36 and from low-temperature separator 39 is fed to reducing devices (throttle) 55 and 59, respectively, to reduce pressure to 3.5-4.0 MPa, after which it is mixed and sent to two-phase separator 57. Low-pressure degassing gas from two-phase separator 57 is sent to reducing device (ejector) 42 as passive gas. The unstable condensate from the two-phase separator 57 is heated in the gas-condensate heat exchanger 29 to a temperature of 20-25°C, sent to the pressure-reducing device (throttle) 63 to reduce the pressure to 3 MPa, mixed with the unstable condensate from the three-phase separator 49 and fed to the three-phase separator 53. The aqueous phase (if any) from the three-phase separator 53 is introduced into the aqueous phase after the three-phase separator 49, the degassing gas from the three-phase separator 53 is fed to the compressor 71 to increase the pressure to 7.0 MPa and is introduced into the gas flow after the primary separator unit 2, and the unstable condensate from the three-phase separator 53 is removed from the unit.

As the production of condensate-containing gas declines and the capacity of the equipment for preparing lean gas is released, parts of the primary separator units 2, adsorbers 4, gas-to-gas heat exchangers 6, compressors 8, air coolers 10 and 14, and turbo-expander units 73 are released.

Formation fluid of gas deposits enters block of primary separators 2 for separation of gas and aqueous phase, which is discharged from the unit. Then gas enters block of adsorbers 4 for extraction of moisture and provision of gas dew point temperature below minus 20°С. Dried gas is heated in block of heat exchangers "gas-gas" 6 to temperature of 15°С and in block of compressors 8 is compressed to pressure of 6.6-7.0 MPa, after which it is cooled in block of air coolers 10 to temperature of 25-30°С. Then gas is compressed in compressor 12 of block of turboexpander unit 73 to pressure of 8.5 MPa, cooled in block of air coolers 14 to temperature of 25-30°С and enters block of heat exchangers "gas-gas" 6, where it is cooled to 20-25°С. The gas is then sent to expander 17 of turbo-expander unit 73 to reduce the pressure to 5.5 MPa and is discharged from the unit at a temperature of minus 3°C.

By changing the sequence of introducing deposits into development and using the equipment of one integrated gas treatment plant to prepare reservoir fluid for gas and gas condensate deposits, there is no longer any need to build a second gas treatment plant with a booster compressor station.

Claims (2)

1. A method for preparing hydrocarbon gas for transportation, including feeding a gas stream from gas condensate well clusters and then to primary separation, adsorption of the aqueous phase from the gas stream, cooling the gas stream with air, low-temperature separation of the gas stream, characterized in that the gas stream from the gas wells and the gas stream from the gas condensate wells are fed separately and prepared separately, the gas stream from the gas wells is fed to primary separation to separate the aqueous phase, which is removed from the unit, and to adsorption drying, then the dried gas is heated with compressed dried gas, compressed and cooled with air, the cooled compressed dried gas is additionally compressed in a turbo expander compressor, sequentially cooled by heat exchange with air and with the dried gas after adsorption drying, as well as by reducing the pressure in the turbo expander expander, after which the cooled dried gas is removed from the plant, wherein the gas flow from the gas condensate wells is fed to separate the liquid phase in the primary separation and adsorption drying, the dried gas is heated with compressed dried gas, then it is compressed and cooled with air, additionally compressed in the turbo expander compressor and successively cooled by heat exchange with air and with the dried gas after adsorption drying, as well as by heat exchange with the unstable condensate and stripped gas, the cooled compressed dried gas is divided into two streams: the first is separated from the condensate and fed to the turbo expander expander for cooling by reducing the pressure and directed to separate the unstable condensate from the gas in the low-temperature separator, and the second is fed to the ejector as an active stream and combined with the first stream after the expander, the stripped gas from the low-temperature separator is heated with compressed dried gas to a temperature of no more than 0 ° C and removed from the plant, the pressure is reduced the pressure of the liquid phase after the primary separation of the gas flow of gas condensate wells and then directing it to separate the aqueous phase and high-pressure degassing gas from the unstable condensate, which is introduced into the cooled gas before the low-temperature separator, the aqueous phase is removed from the unit, the pressure of the unstable condensate is reduced and directed to separate the flash gas and residual water, which is introduced into the aqueous phase and removed from the unit, the pressure of the liquid hydrocarbon phase after the low-temperature separation is reduced and directed to separate the low-pressure degassing gas from the unstable condensate, which is then heated with compressed dried gas of gas condensate wells and combined with the unstable condensate isolated from the liquid phase after the primary separation of the gas flow of gas condensate wells, the unstable condensate separated from the flash gas and residual water is removed from the unit, the low-pressure degassing gas is directed to the ejector as a passive flow, the flash gas is compressed and introduced into gas flow from gas condensate wells after primary separation. 2. The method according to paragraph 1, characterized in that the cooled compressed dried gas is divided into two streams: the first stream constitutes 90% of the total volume of the divided stream, and the second stream constitutes 10% of the total volume of the divided stream.

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