Abstract: The invention concerns a subsea heat exchanger for cooling or heating a hydrocarbon-containing fluid, said heat exchanger comprising: a convection section enclosed by a shell or enclosure comprising: one or more heat exchanging fluid inlet(s) and outlet(s); one or more hydrocarbon-containing fluid inlet(s) and outlet(s); and one or more fluid carrying convection tube(s) adapted for heat transfer between the hydrocarbon-containing fluid on the inside of the tube(s) and a surrounding heat exchanging fluid on the opposite side of the tube(s), wherein the heat exchanger is provided with one or more flow regulating device(s) for controlling the hydrocarbon-containing fluid outlet temperature, wherein the heat exchanging fluid circulates in a closed circuit for heat transfer both with said hydrocarbon-containing fluid and with surrounding sea water on the outside of the enclosure. The invention also concerns a method for subsea cooling or heating of a hydrocarbon containing fluid.

Abstract: The present invention concerns a method for lowering the water dew point subsea in a produced multiphase hydrocarbon fluid stream containing water, the method comprising the steps of: separating (10) the hydrocarbon fluid stream (1) into a liquid phase (3) and a first gas phase (2); cooling (20) the first gas phase in a controlled manner to knock out water or condensing water and optionally other condensates while keeping the fluid above a hydrate formation temperature thereof; separating off condensed liquids (6) and a second gas phase; wherein the second gas phase (8) has a water dew point which is lower than that of the initial multiphase hydrocarbon fluid stream. The invention also concerns a system for lowering the water dew point subsea.

Abstract: A scrubber for separation of liquid phase and any other constituents from a fluid now that in substance includes a gas. The scrubber is formed as a standing vessel with round cross section, with an outlet for liquid from the bottom and an outlet for gas from the top. The scrubber is distinguished in includes a fluid inlet that either is tangentially oriented relative to the inner wall of the scrubber or equipped with a deflection plate, such that introduced fluid is directed tangentially horizontal or with a small downward slope along the inner wall of the scrubber, into and through a fluid way arranged as a downwards directed spiral within the scrubber, along the inner wall, from a level over or at the inlet to a level at or close to the outlet for liquid, with an opening for gas escape inwards toward the center of the scrubber. The scrubber according to the invention results in very low liquid entrainment.

Abstract: A method of liquefying a hydrocarbon-rich gas, wherein the gas flows through a cascade of three refrigeration stages, each stage comprising a refrigerant circuit and a compressor, wherein at least part of the flow of refrigerant from the second circuit is used for the pre-cooling of the hydrocarbon rich gas in the first refrigeration stage. This balances the load on each of the compressors. By standardizing the drive units and compressors of the three coolant circuits, it is possible to maximize the attainable liquefaction capacity of the liquefaction process using tried-and-trusted drive units and compressors respectively. This method can be applied to mixed refrigerant cascades and circuits with a carbon dioxide pre-cooling circuit. This latter option has benefits for offshore use where large amounts of hydrocarbons are undesirable.

Abstract: In the liquefaction of a hydrocarbon by indirect heat exchange with the refrigerant mixture of a refrigerant mixture cycle, the refrigerant mixture being compressed in multiple stages, the compressed refrigerant mixture (23) is at least partially condensed (E4) downstream of the penultimate compressor stage and is fractionated (D4) into a higher-boiling liquid fraction (26) and a lower-boiling gas fraction (24). The lower-boiling gas fraction (24) is compressed to the final pressure, partially condensed (E5) and fractionated (D5) into a lower-boiling gas fraction (10) and a higher-boiling liquid fraction (27). The higher-boiling liquid fraction (27) is added to the partially condensed refrigerant mixture stream (23), and the gas fraction (10) forms the lower-boiling refrigerant mixture fraction and the liquid fraction (26) forms the higher boiling refrigerant mixture fraction of the refrigerant mixture cycle.

Abstract: The invention relates to a method for liquefying a stream rich in hydrocarbons, especially a stream of natural gas, by the indirect exchange of heat with the refrigerants in a closed-circuit cascade of mixed refrigerants. According to the invention, said closed-circuit cascade of mixed refrigerants consists of at least 3 circuits of mixed refrigerants, with each circuit comprising different refrigerants. The first of the three mixed refrigerant circuits is used for pre-cooling (E1), the second for liquefying E2), and the third for super-cooling (E3) the hydrocarbon-rich stream (1) to be liquefied. The method provided for in the invention reduces specific energy consumption and investment costs since the three circuits of mixed refrigerants are or can be optimally adjusted to the enthalpy temperature curves of the hydrocarbon-rich stream to be liquefied and the refrigerant mixtures.

Abstract: A method and a system for offshore production of liquefied natural gas, wherein natural gas is supplied from an underground source to a field installation for gas treatment. The gas is transferred in compressed form from the field installation to an LNG tanker. The transfer takes place via a pipeline surrounded by sea water. The compressed gas is supplied to a conversion plant which is provided on the LNG tanker and is arranged to convert at least a part of the gas to liquefied form, and the liquified gas is transferred to storage tanks on board the tanker. When the storage tanks on the LNG tanker are filled up, the pipeline is disconnected from the LNG tanker and connected to another, similar tanker. The pipeline is permanently connected to a submerged buoy which is arranged for introduction and releasable securement in a submerged downwardly open receiving space in the tanker, and which is provided with a swivel unit for transfer of gas under a high pressure.

Abstract: A method and a system for offshore production of liquefied natural gas, wherein natural gas is supplied from an underground source (4) to a subsea production plant (1). The gas is transferred under a high pressure directly from the production plant (1) to an LNG tanker (6), the transfer taking place through a pipeline (5) surrounded by sea water and causing the temperature of the high pressure gas to be lowered to a desired low temperature. This gas is supplied to a conversion plant (12) provided on the LNG tanker (16) and arranged for converting at least a part of the gas to liquid form, and the liquefied gas is transferred to storage tanks (17) on board the vessel (6).