Subsea hydrocarbon flowline system and related method and use

1. A subsea hydrocarbon flowline system comprising:

a hydrocarbon flowline;

an electric trace heating system arranged along at least a part-length of the flowline to control the temperature of hydrocarbon fluid flowing in the flowline; and

a power input connector (Pin) configured for receiving electrical power from an electrical power providing system for powering the electric trace heating system;

wherein the electric trace heating system comprises a first three-phase trace heating cable (C′) and a second three-phase trace heating cable (C″), each trace heating cable (C′; C″) comprising three phase conduits (L 1 ′, L 2 ′, L 3 ′; L 1 ″, L 2 ″, L 3 ″) and extending between the power input connector (Pin) and a cable termination (T′; T″) at which the phase conduits (L 1 ′, L 2 ′, L 3 ′; L 1 ″, L 2 ″, L 3 ″) are Y-connected and terminate in a neutral connection point (LN′; LN″); and

wherein the flowline system further comprises:

a power output connector (Pout) for providing electrical power to a subsea hydrocarbon production system;

a first electrical conduit extending between the neutral connection point (LN′) of the cable termination (T′) of the first trace heating cable (C′) and the power output connector (Pout); and

a second electrical conduit extending between the neutral connection point (LN″) of the cable termination (T″) of the second trace heating cable (C″) and the power output connector (Pout);

wherein the first and the second electrical conduits are electrically accessible at the power output connector (Pout) for powering the subsea hydrocarbon production system.

2. The flowline system according to claim 1 , further comprising:

a signal conduit for providing control signals to and receiving control and/or monitoring signals from the subsea hydrocarbon production system;

wherein the signal conduit extends between and is accessible at the power input connector (Pin) and the power output connector (Pout).

3. The flowline system according to claim 1 , wherein the trace heating cables (C′, C″) are utilised to provide control signals to and receive control and/or monitoring signals from the subsea hydrocarbon production system.

4. The flowline system ( 300 ) according to claim 1 , further comprising:

a carrier pipe in which the flowline is arranged;

wherein the first and second three-phase trace heating cables (C′;

C″) are arranged in an annular space formed between the flowline and the carrier pipe.

5. A hydrocarbon processing system comprising:

a flowline system according to any one of claims 1 - 4 ;

an electrical power providing system connected to said power input connector (Pin) for providing electrical power to said electric trace heating system; and

a subsea production system connected to said power output connector (Pout);

wherein the subsea production system is configured for receiving electrical power from the electrical power providing system via said first and second electrical conduits.

6. A method of providing electrical power to a subsea hydrocarbon production system, the method comprising the steps of:

arranging a flowline system according to any one of claims 1 - 4 subsea;

connecting the power input connector (Pin) of the flowline system to an electrical power providing system;

connecting the subsea hydrocarbon production system to the power output connector (Pout) of the flowline system; and

providing electrical power to the subsea hydrocarbon production system from the electrical power providing system via the trace heating cables (C′, C″) of the flowline system.

7. The method according to claim 6 , further comprising the step of providing control signals to and receiving control and/or monitoring signals from the subsea hydrocarbon production system via a signal conduit extending between and being accessible at the power input connector (Pin) and the power output connector (Pout).

8. A hydrocarbon processing system comprising:

a flowline system comprising:

a hydrocarbon flowline;

an electric trace heating system arranged along at least a part-length of the flowline to control the temperature of hydrocarbon fluid flowing in the flowline; and

a power input connector (Pin);

wherein the electric trace heating system comprises a first three-phase trace heating cable (C′) and a second three-phase trace heating cable (C″), each trace heating cable (C′; C″) comprising three phase conduits (L 1 ′, L 2 ′, L 3 ′; L 1 ″, L 2 ″, L 3 ″) and extending between the power input connector (Pin) and a cable termination (T′; T″) at which the phase conduits (L 1 ′, L 2 ′, L 3 ′; L 1 ″, L 2 ″, L 3 ″) are Y-connected and terminate in a neutral connection point (LN′; LN″);

a power output connector (Pout) for providing electrical power to a subsea hydrocarbon production system;

a first electrical conduit extending between the neutral connection point (LN′) of the cable termination (T′) of the first trace heating cable (C′) and the power output connector (Pout); and

a second electrical conduit extending between the neutral connection point (LN″) of the cable termination (T″) of the second trace heating cable (C″) and the power output connector (Pout);

wherein the first and the second electrical conduits are electrically accessible at the power output connector (Pout) for powering the subsea hydrocarbon production system;

an electrical power providing system connected to said power input connector (Pin) for providing electrical power to said electric trace heating system; and

a subsea production system connected to said power output connector (Pout);

wherein the subsea production system is configured for receiving electrical power from the electrical power providing system via said first and second electrical conduits; and

wherein the electrical power providing system comprises:

a first three-phase power source (P′) for powering the first three-phase cable (C′), wherein the first power source (P′) is configured to form a Y-Y connection with the first trace heating cable (C′);

a second three-phase power source (P″) for powering the second three-phase cable (C″), the second power source (P″) being configured to form a Y-Y connection with the second trace heating cable (C″); and

a single-phase power source (P SPS ) arranged between neutral connection points (PN′; PN″) of the first and second three-phase power sources (P′, P″).

9. The hydrocarbon processing system according to claim 8 , wherein the first trace heating cable (C′) is configured for operating at a first neutral voltage level (V N ′) and the second trace heating cable (C″) is configured for operating at a second neutral voltage level (V N ″) being different from the neutral voltage level (V N ′) of the first trace heating cable (C′).

10. The hydrocarbon processing system according to claim 9 , wherein a difference between the neutral voltage level (V N ′) of the first trace heating cable (C′) and the neutral voltage level (V N ″) of the second trace heating cable (C″) is an AC voltage (V SPS ) or a DC voltage.

11. The hydrocarbon processing system according to claim 8 , wherein the flowline system further comprises:

a signal conduit for providing control signals to and receiving control and/or monitoring signals from the subsea hydrocarbon production system;

wherein the signal conduit extends between and is accessible at the power input connector (Pin) and the power output connector (Pout).

12. The hydrocarbon processing system according to claim 8 , wherein the trace heating cables (C′, C″) are utilised to provide control signals to and receive control and/or monitoring signals from the subsea hydrocarbon production system.

13. The hydrocarbon processing system according to claim 8 , wherein the flowline system further comprises:

a carrier pipe in which the flowline is arranged;

wherein the first and second three-phase trace heating cables (C′; C″) are arranged in an annular space formed between the flowline and the carrier pipe.

14. Use of first and second three-phase trace heating cables (C′, C″) of an electrical trace heating system of a subsea hydrocarbon flowline system for powering a subsea hydrocarbon production system connected to a power output connector (Pout) of the subsea hydrocarbon flowline system, the subsea hydrocarbon flowline system comprising:

a hydrocarbon flowline;

the electric trace heating system being arranged along at least a part-length of the flowline to control the temperature of hydrocarbon fluid flowing in the flowline; and

a power input connector (Pin) configured for receiving electrical power from an electrical power providing system for powering the electric trace heating system;

wherein each trace heating cable (C′; C″) comprises three phase conduits (L 1 ′, L 2 ′, L 3 ′; L 1 ″, L 2 ″, L 3 ″) and extends between the power input connector (Pin) and a cable termination (T′; T″) at which the phase conduits (L 1 ′, L 2 ′, L 3 ′; L 1 ″, L 2 ″, L 3 ″) are Y-connected and terminate in a neutral connection point (LN′; LN″); and

wherein the flowline system further comprises:

a first electrical conduit extending between the neutral connection point (LN′) of the cable termination (T′) of the first trace heating cable (C′) and the power output connector (Pout); and

a second electrical conduit extending between the neutral connection point (LN″) of the cable termination (T″) of the second trace heating cable (C″) and the power output connector (Pout);

wherein the first and the second electrical conduits are electrically accessible at the power output connector (Pout) for powering the subsea hydrocarbon production system.