AU2012296868B2

AU2012296868B2 - System and method for producing a hydrocarbon product stream from a hydrocarbon well stream, and a hydrocarbon well stream separation tank

Info

Publication number: AU2012296868B2
Application number: AU2012296868A
Authority: AU
Inventors: Johan Jan Barend Pek
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2011-08-18
Filing date: 2012-08-17
Publication date: 2015-08-27
Anticipated expiration: 2032-08-17
Also published as: CN103748317B; BR112014002410B1; CN103748317A; AU2012296868A1; EP2744978A1; WO2013024147A1; KR20140063685A; AP2014007385A0; KR101953939B1; BR112014002410A2

Abstract

A hydrocarbon well stream separation tank is employed for handling a hydrocarbon well stream. The tank has a lower compartment (102) for separating a liquid of a liquid phase from a vaporous hydrocarbon phase of the hydrocarbon well stream and an inlet (110) for allowing the hydrocarbon well stream to flow from outside of the hydrocarbon well stream separation tank into the lower compartment of the hydrocarbon well stream separation tank. The tank further has an upper compartment (104) located gravitationally above the lower compartment, and an internal passage (106) fluidly connecting the lower compartment and the upper compartment. A filter (108), capable of filtering mercury from the vaporous hydrocarbon phase, is disposed in the upper compartment.

Description

WO 2013/024147 - 1 - PCT/EP2012/066064 SYSTEM AND METHOD FOR PRODUCING A HYDROCARBON PRODUCT STREAM FROM A HYDROCARBON WELL STREAM, AND A HYDROCARBON WELL STREAM SEPARATION TANK The present invention relates to a system and method for producing a hydrocarbon product stream from a hydrocarbon well stream. In a further aspect, the present invention relates to a hydrocarbon well stream 5 separation tank. Such hydrocarbon well stream separation tank may be used in or form part of the systems and/or methods disclosed herein. Hydrocarbon well streams produced from subterranean earth formations often contain natural gas and/or crude 10 oils, and an aqueous phase containing water. The natural gas is usually contaminated with non-hydrocarbon molecules, including acid molecules such as carbon dioxide CO 2 and sulphur compounds such as H 2 S. However, in addition to that, hydrocarbon well streams produced in 15 certain areas of the world may contain mercury in quantities sufficient to render their processing problematical. The mercury is not only present in the produced water and/or the crude oils, but it may also be present the in natural gas. 20 US Patent 4,982,050 discloses a method and system wherein raw natural gas is treated prior to its liquefaction. In addition to a Hg cold trap disposed in substantially the coldest point in the system before a main heat exchanger, a separate Hg remover is provided to 25 remove the bulk of the mercury contamination present in the natural by contacting the natural gas in a treating bed, before the gas is contacted with equipment that is easily damaged by mercury or produce vapours for release 2 in the environment that may otherwise contain mercury. The effluent gas from the mercury remover is carried through carbon dioxide and hydrogen sulphide removal units. Patent application publication US 2010/0032344 discloses a process for decreasing the level of elemental mercury contained in a crude oil at the well site. Crude oil from a crude oil well is passed to a separator for separation into a gaseous hydrocarbon stream containing hydrocarbons, mercury and water, and into a liquid hydrocarbon stream. Both the gaseous hydrocarbon stream and liquid hydrocarbon stream are removed from the separator. A mercury containing gas feed, including in part at least a portion of gaseous hydrocarbon stream removed from the separator, is charged to a mercury removal unit that is arranged as a separate unit. In particular in an offshore environment, plot space is scarce and expensive. Hence, the known methods are not very attractive for application in an offshore environment, such as for example on an offshore hydrocarbon fluid production platform, for instance in the form of a floating production storage and offloading structure and/or a floating liquefied natural gas production structure. It is an object of the invention to improve upon the prior art at least to an extent or to provide a suitable alternative thereto. In a first aspect, there is provided a method of producing a hydrocarbon product stream from a hydrocarbon well stream, comprising the steps of: - producing a hydrocarbon well stream from a subterranean earth formation, said hydrocarbon well stream comprising at least a vaporous hydrocarbon phase and a liquid phase; - feeding the hydrocarbon well stream into a lower compartment of a hydrocarbon well stream separation tank; 3 - in said lower compartment allowing a liquid from the liquid phase to separate from the vaporous hydrocarbon phase; - discharging the liquid from the hydrocarbon well stream separation tank via a liquid discharge outlet; - passing the vaporous hydrocarbon phase to an upper compartment within the hydrocarbon well stream separation tank via an internal passage, wherein the internal passage is located gravitationally higher than the liquid discharge outlet and wherein the upper compartment is located gravitationally above the lower compartment; - passing the vaporous hydrocarbon phase through a filter disposed in the upper compartment of the hydrocarbon well stream separation tank; - accumulating mercury from the vaporous hydrocarbon phase in said filter; - discharging a filtered vaporous hydrocarbon stream from said upper compartment, said filtered vaporous hydrocarbon stream comprising a hydrocarbon molecules containing vapour from the vaporous hydrocarbon phase without the mercury that has accumulated in the filter; - further processing the filtered vaporous hydrocarbon stream to produce a hydrocarbon product stream from said filtered vaporous hydrocarbon stream. In another aspect, there is provided a hydrocarbon well stream separation tank comprising: - a lower compartment for separating a liquid of a liquid phase from a vaporous hydrocarbon phase of a hydrocarbon well stream; - an inlet for allowing the hydrocarbon well stream to flow from outside of the hydrocarbon well stream separation tank into the lower compartment of the hydrocarbon well stream separation tank; 4 - a liquid discharge outlet for discharging the liquid from the hydrocarbon well stream separation tank; - an upper compartment located gravitationally above the lower compartment; - an internal passage fluidly connecting the lower compartment and the upper compartment, wherein the internal passage is located gravitationally higher than the liquid discharge outlet; - a discharge outlet for discharging a filtered vaporous hydrocarbon stream from the upper compartment to outside of the hydrocarbon well stream separation tank; - a filter, capable of filtering mercury from the vaporous hydrocarbon phase, disposed in the upper compartment wherein the internal passage is fluidly separated from the discharge outlet such that the vaporous hydrocarbon phase must pass through the filter before being discharged from the lower compartment through the discharge outlet. In still another aspect, there is provided a system for producing a hydrocarbon product stream from a hydrocarbon well stream, comprising: - the hydrocarbon well stream separation tank as described above, or herein below; - hydrocarbon processing means fluidly connected to the discharge outlet of said hydrocarbon well stream separation tank and arranged to receive the filtered vaporous hydrocarbon stream and to produce a hydrocarbon product stream from said filtered vaporous hydrocarbon stream. The present invention will now be further illustrated by way of preferred example, and with reference to the accompanying non-limiting drawings, in which: WO 2013/024147 - 5 - PCT/EP2012/066064 Figure 1 schematically shows a system for producing a hydrocarbon product stream from a hydrocarbon well stream embodying the invention; Figure 2 schematically shows an embodiment of a 5 hydrocarbon well stream separation tank that can be used in the system of Figure 1; Figure 3 schematically shows another embodiment of a hydrocarbon well stream separation tank that can be used in the system of Figure 1; 10 Figure 4 schematically shows an embodiment of a hydrocarbon processing means that can be used in the system of Figure 1. For the purpose of this description, a single reference number will be assigned to a line as well as a 15 stream carried in that line. The same reference numbers refer to similar components, streams or lines. The person skilled in the art will readily understand that, while the invention is illustrated making reference to one or more a specific combinations of features and 20 measures, many of those features and measures are functionally independent from other features and measures such that they can be equally or similarly applied independently in other embodiments or combinations. The present disclosure describes methods and systems 25 for producing a hydrocarbon product stream from a hydrocarbon well stream. The methods and systems involve a hydrocarbon well stream separation tank comprising a lower compartment for phase separating a hydrocarbon well stream, and an upper compartment for filtering mercury 30 from the vaporous hydrocarbon phase separated from the hydrocarbon well stream before discharging it from the hydrocarbon well stream separation tank in the form of a filtered vaporous hydrocarbon stream. The hydrocarbon WO 2013/024147 - 6 - PCT/EP2012/066064 product stream may be obtained by subjecting at least part of the filtered vaporous hydrocarbon stream to further processing of any type or combination of process types. 5 In the context of the present disclosure, a filter is intended to cover any type of device that can physically or chemically retain mercury and/or mercury containing compounds while letting other molecules through. In the context of mercury removal, such filter may suitably be a 10 sorption filter. Such filter may be embodied in various forms. In one preferred example it takes the form of a porous material, for instance in bulk form or in the form of granules, through which the vaporous hydrocarbon phase can pass while mercury and/or mercury containing 15 compounds are retained. In another example it may take the form of a membrane. By combining inlet phase separating and mercury removal from the resulting vaporous hydrocarbon phase, a relatively compact and efficient solution is provided to 20 prepare a vaporous hydrocarbon stream with reduced mercury content that can be used as feed stream for any kind of further hydrocarbon processing process. The presently disclosed methods and systems are not only useful in an offshore environment where plot space 25 is scarce and expensive, but they may also be usefully applied in an onshore environment. In the context of the present specification, the term "subterranean formation" refers to earth formations that can be located offshore or onshore. 30 Figure 1 schematically illustrates a method and system for producing a hydrocarbon product stream 90 from a hydrocarbon well stream 10.

WO 2013/024147 - 7 - PCT/EP2012/066064 The hydrocarbon well stream is provided through an upstream production conduit 10 from a hydrocarbon reservoir 520 in a subterranean formation 530. The hydrocarbon well stream comprises a vaporous hydrocarbon 5 phase, which may contain "raw" natural gas, and a liquid phase. The liquid phase may comprise a liquid aqueous phase containing water and a liquid hydrocarbon phase. A non-hydrocarbon solid phase, such as sand, may also be contained in the hydrocarbon well stream. The aqueous 10 phase may contain mercury and/or other minerals and other constituents dissolved therein that originate from the subterranean earth formation, as well as an additive. A common additive is a hydrate inhibitor. The vaporous hydrocarbon phase may contain one or 15 more of the group consisting of methane, ethane, propane, butanes, and pentanes. In addition, it may contain non hydrocarbon molecules, including acid molecules such as carbon-dioxide C02 and sulphur compounds such as H 2 S, and mercury. 20 Referring again to Figure 1, the system further comprises a well stream separation tank 100 fluidly connected, via a main inlet 110, to the upstream production conduit 10 to receive the hydrocarbon well stream and to separate the hydrocarbon well stream into 25 at least one intermediate product stream 40 comprising molecules from the vaporous hydrocarbon phase, and an intermediate waste stream 50 comprising the aqueous phase. Optionally, the well stream separation tank 100 may be embodied in the form of a three phase 30 separator, wherein the hydrocarbon well stream 10 may be separated into more streams than described above. Typically such more streams may include, in addition to the streams described above, a liquid hydrocarbon phase WO 2013/024147 - 8 - PCT/EP2012/066064 20, and/or including a solids-containing stream (not shown). Accordingly, the three phase separator may comprise an aqueous phase discharge outlet 150 arranged to selectively discharge the liquid aqueous phase from 5 the hydrocarbon well stream separation tank 100, and a hydrocarbon phase discharge outlet 120 arranged to selectively discharge the liquid hydrocarbon phase from the hydrocarbon well stream separation tank 100 separately from the liquid aqueous phase. Usually, the 10 hydrocarbon phase discharge outlet 120 is arranged gravitationally higher than the aqueous phase discharge outlet 150 to allow for separation of these two liquid phases based on density differences. Solids may be discharged together with the liquid aqueous phase, or via 15 an optional solids phase discharge outlet (not shown). Separate units or systems may be provided to handle such liquid hydrocarbon phase 20 and liquid aqueous phase, depending on the specific needs and requirements. For instance, a hydrocarbon condensate stabilisation unit 20 600 may be provided to receive the liquid hydrocarbon phase 20 and remove relatively volatile constituents 35 from it so that the remaining stabilised liquid 30 can be stored safely under atmospheric pressure and temperature. Intermediate waste stream 50 comprising the aqueous 25 phase may similarly be purified. For instance, a hydrate inhibitor regeneration unit 200 may be provided, which at its upstream side is connected to the hydrocarbon well stream separation tank 100 to receive the intermediate waste stream 50. A regenerated hydrate inhibitor stream 30 65, which comprises a higher concentration of the hydrate inhibitor additive than the aqueous phase of the intermediate waste stream 50, is discharged from the hydrate inhibitor regeneration unit 200. At least part WO 2013/024147 - 9 - PCT/EP2012/066064 of the residue portion of the intermediate waste stream 50, generally a water stream comprising a lower concentration of the hydrate inhibitor additive than the aqueous phase of the intermediate waste stream 50, is 5 discharged as the waste stream portion 60 into a waste stream conduit. The hydrocarbon well stream separation tank 100 is further provided with a vaporous hydrocarbon stream discharge outlet, hereinafter referred to as vapor 10 discharge outlet 140, for discharging intermediate product stream 40 comprising vapor with molecules from the vaporous hydrocarbon phase from the hydrocarbon well stream separation tank 100. The vaporous hydrocarbon phase comprises at least hydrocarbon molecules, 15 preferably including methane molecules. Hydrocarbon processing means 400 are arranged to receive the intermediate product stream 40 and to further process the intermediate product stream 40 to produce the hydrocarbon product stream 90 from the intermediate 20 product stream 40. In addition to the hydrocarbon product stream 90, the hydrocarbon processing means 400 may produce one or more by-product streams 95. Further details and example embodiments will be discussed later herein, with reference to Figure 4. 25 In order to prevent damage by or contamination of equipment or streams in the hydrocarbon processing means 400, an amount of mercury is selectively removed from the vaporous hydrocarbon phase separated out from the hydrocarbon well stream 10, before parts of the vaporous 30 hydrocarbon phase reach the hydrocarbon processing means 400. Figures 2 and 3 schematically show advantageous embodiments hydrocarbon well stream separation tanks WO 2013/024147 - 1 0 - PCT/EP2012/066064 wherein the functions of phase separation of the hydrocarbon well stream 10 into at least a liquid phase 103 and at least a vaporous hydrocarbon phase 107, and of mercury removal from the separated vaporous hydrocarbon 5 phase 107 can be combined in one tank, such that both functions can be carried out in the plot space that normally is allocated for the phase separation step alone. In each of the embodiments of Figures 2 and 3, the 10 hydrocarbon well stream separation tank 100 comprises a lower compartment 102 for separating the liquid phase 103 from the vaporous hydrocarbon phase 107 of the hydrocarbon well stream 10 that has been allowed into the hydrocarbon well stream separation tank 100 via main 15 inlet 110. The main inlet 110 may be associated with usual internals including an inlet distributor 112. The lower compartment is essentially a gas/liquid phase separator, optionally in the form of a three-phase separator. 20 At least one liquid discharge outlet is provided in a lower part of the lower compartment to discharge a least part of the liquid phase 103 from the hydrocarbon well stream separation tank 100. In the embodiment of Figures 2 and 3 this liquid discharge outlet is shown in the form 25 of the aqueous phase discharge outlet 150 arranged to selectively discharge the liquid aqueous phase from the hydrocarbon well stream separation tank 100. The hydrocarbon well stream separation tank 100 further comprises an upper compartment 104, located 30 gravitationally above the lower compartment 102. An internal passage 106 fluidly connects the lower compartment 102 and the upper compartment 104. The internal passage 106 is located gravitationally higher WO 2013/024147 - 1 1 - PCT/EP2012/066064 than the liquid discharge outlet. It functions as a vapour phase discharge outlet of the lower compartment 102, and it may optionally be associated with internals that are more common in gas/liquid phase separators such 5 as a mist mat or similar means to prevent cross-over of liquid droplets. A filter 108 is disposed in the upper compartment 104. The filter is preferably a selective filter, capable of filtering mercury from the vaporous 10 hydrocarbon phase 107, for instance by virtue of chemical and/or physical differences of mercury and/or mercury compounds compared to hydrocarbon molecules, in particular compared to methane. Furthermore, a vapor discharge outlet 140 is provided in the upper compartment 15 104 for discharging a filtered vaporous hydrocarbon stream 109 from the upper compartment 104 to outside of the hydrocarbon well stream separation tank 100. The filter 108 is arranged such that the internal passage 106 is fluidly separated from the vapor discharge outlet 140 20 such that the vaporous hydrocarbon phase 107 must pass through the filter 108 before being discharged from the lower compartment 104 through the vapor discharge outlet 140. The filter 108 is suitably a sorption filter. It may 25 comprise a sorbent material, preferably a solid sorbent material that is capable of sorbing mercury from the vaporous hydrocarbon phase 107. Many suitable sorbent materials are known for stand-alone mercury removal units, including activated carbon, activated zeolite, 30 alumina, silica, or chemically modified versions of such materials using a chemical promoter, including for example sulfur, iodine, chlorine, nitric acid, metal sulfide such as copper sulfide and zinc sulfide, and WO 2013/024147 - 12 - PCT/EP2012/066064 mixed sulfide, to enhance the sorption selectivity for mercury sorption. For reasons of operational simplicity, a non-regenerative sorbent may be selected for this purpose. This allows operation of the hydrocarbon well 5 fluid separator tank 100 during a number of years during which mercury accumulates in the sorbent filter, after which the filter is replaced during a scheduled maintenance shut down period. The embodiment of Figure 2 differs from the 10 embodiment of Figure 3 that in case of Figure 3 the internal passage 106 extends through the filter allowing the vaporous hydrocarbon phase 107 to pass through the filter 108 without effectively contacting the filter and then to pass through the filter in a contacting mode in a 15 generally downward direction. In this case, the vapor discharge outlet 140 can be below the filter 108, suitably located in a side wall of the hydrocarbon well stream separation tank 100. In the case of Figure 3, the internal passage 106 is shorter and it does not extend 20 through the filter 108. The vaporous hydrocarbon phase 107 must pass through the filter 108 in a generally upward direction. The vapor discharge outlet 140 can be above the filter 108, suitably in an overhead area of the hydrocarbon well stream separation tank 100. 25 Suitably, the hydrocarbon well stream separation tank 100 is constructed in the form of an upright, for example vertically, extending pressurizable tank having a cylindrically shaped side wall section extending around an upright central axis. The upper compartment 104 and 30 the lower compartment 102 may optionally be separated by a separator plate 114 disposed inside the side wall section generally transverse to the upright central axis. It does not have to be a flat plate: for instance it may WO 2013/024147 - 13 - PCT/EP2012/066064 be upwardly or downwardly protruding frusto-conically shaped around the central axis (not shown). The internal passage 106 may be as simple as merely an opening in the separator plate 114. Preferably, the internal passage 5 106 does not impart a significant pressure loss in the vaporous hydrocarbon phase 107. Passage through the filter 108 may cause a pressure drop. Any pressure drop may call for a re-compression need, for more efficient hydrocarbon processing in the hydrocarbon processing 10 means 400. Hence, the smaller the pressure drop that is imposed by passing the vaporous hydrocarbon phase 107 to the filter 108, the more pressure is available for allowing a pressure drop over the filter 108. Suitably, the pressure in the upper compartment 104 upstream of the 15 filter is less than 1 bar, preferably less than 0.5 bar, lower than the pressure in the lower compartment 102. Referring again to Figure 1, the hydrocarbon processing means 400 may consist of any number of units of various types, as necessary to further process the 20 intermediate product stream 40 into the desired hydrocarbon product stream having the desired specification. The intermediate product stream 40, formed out of the filtered vaporous hydrocarbon stream 109, may contain 25 varying amounts of hydrocarbons from the group consisting of methane, ethane, propane, and butanes. Possibly it may further contain lesser amounts of pentanes and aromatic hydrocarbons. The composition varies depending upon the type and location of the gas. It is preferably 30 comprised substantially of methane. Preferably the gaseous hydrocarbon stream 10 comprises at least 50 mol% methane, more preferably at least 80 mol% methane.

WO 2013/024147 - 1 4 - PCT/EP2012/066064 The intermediate product stream 40 may further contain non-hydrocarbons such as H 2 0, N 2 , C02, Hg, H 2 S and other sulphur compounds, and the like. Thus, the hydrocarbon processing means may comprise units or 5 systems for reduction and/or removal of undesired components such as C02 and H 2 S, and/or other steps such as early cooling, pre-pressurizing or the like. As these steps are well known to the person skilled in the art, their mechanisms are not further discussed here. 10 In one example illustrated in Figure 4, wherein the hydrocarbon processing means 400 comprises a liquefaction system 440, the hydrocarbon product stream 90 may be a liquefied natural gas stream while a natural gas liquids stream (e.g. a liquefied petroleum gas stream for the 15 majority consisting of propane and/or butane) may be one of the one or more by-product streams 95. The liquefaction system 440 is typically arranged to extract heat from at least part of the intermediate product stream 40, thereby producing the hydrocarbon product 20 stream 90 in liquefied form, such as in the form of a liquefied hydrocarbon stream. Instead of, or in addition to, the liquefaction system 440, the further processing in the hydrocarbon processing means 400 may include one or more of the group 25 consisting of: residual mercury removal 430; dehydration 420; acid component removal 410 including C02 removal and/or H 2 S removal and/or respective recovery; extraction and/or recovery of natural gas liquids to produce a leaner natural gas stream to be transformed into said 30 liquefied form; nitrogen removal; helium removal and/or helium recovery. Of all the possible units in the hydrocarbon processing means 400, the acid component removal unit 410 WO 2013/024147 - 1 5 - PCT/EP2012/066064 (sometimes referred to as acid gas removal unit - AGRU) may be closest to the hydrocarbon well stream separation tank 100. It may be fluidly connected to the vapor discharge outlet 140 of the hydrocarbon well stream 5 separation tank 100, without any other composition modifying unit in between. Common acid components to be removed are hydrogen sulfide (H 2 S) and carbon dioxide (C02). The acid component removal unit advantageously comprises an amine solvent unit arranged to contact at 10 least part of the intermediate stream 40 with an amine solvent. Since the intermediate product stream 40 is formed out of the filtered vaporous hydrocarbon stream 109, it contains a lower concentration of mercury than the 15 vaporous hydrocarbon phase 107 from the hydrocarbon well stream 10. Thus, less mercury is adsorbed in the amine and building up in the amine regeneration unit or being vented to atmosphere when using a hydrocarbon well stream separation tank 100 as described herein than when using a 20 conventional inlet separator or conventional three-phase separator. This allows handling of gas from hydrocarbon reservoirs that have higher than average mercury content. Various processes and installations are known for each of the further processing steps identified above, 25 and need not be explained herein. During operation, the system described above works as follows. The hydrocarbon well stream 10 is produced from the hydrocarbon reservoir 520 from the subterranean earth 30 formation 530. The hydrocarbon well stream 10 comprises at least a vaporous hydrocarbon phase and a liquid phase. The produced hydrocarbon well steam 10 is fed into the lower compartment 102 of the well stream separator tank WO 2013/024147 - 16 - PCT/EP2012/066064 100, wherein it is allowed to separate into a liquid 103 from the liquid phase and the vaporous hydrocarbon phase 107. The liquid 103 is discharged from the hydrocarbon well stream separation tank 100 via the liquid discharge 5 outlet 150 in the bottom of the hydrocarbon well stream separation tank 100. The vaporous hydrocarbon phase 107 is passed to the upper compartment 104 via the internal passage 106. From the internal passage 106 it is next passed through the 10 filter 108 that is disposed the upper compartment 104. Mercury from the vaporous hydrocarbon phase 107 is retained in the filter 108 where it may be allowed to accumulate. The resulting filtered vaporous hydrocarbon stream 109, which comprises the vaporous hydrocarbon 15 phase without the mercury that has accumulated in the filter, is discharged from the upper compartment 104 via the vapor discharge outlet 140 to form the intermediate product stream 40. Preferably, the majority of the mercury in the vaporous hydrocarbon phase 107 is filtered 20 out in the filter 108. The intermediate product stream 40 is further processed to produce the hydrocarbon product stream 90 from the intermediate product stream 40. It follows from the above that the intermediate product stream 40 may first be deriched from one or more 25 acid components, for instance by contacting the intermediate product stream 40 with an amine solvent. A well known example of a liquefied hydrocarbon stream is a liquefied natural gas stream, which typically contains mostly methane, such as at least 80 mol% 30 methane. In such a case, the further processing may comprise removing heat from at least a methane-containing portion of the intermediate product stream 40 to form a hydrocarbon product stream in the form of a liquefied WO 2013/024147 - 1 7 - PCT/EP2012/066064 methane-containing stream such as a liquefied natural gas stream. A variety of suitable installations and line ups are available in the art for extracting heat from a vaporous hydrocarbon containing feed stream, particularly 5 a natural gas stream, as well as other treatment steps such as those briefly described above for the removal of unwanted contaminants and components from the feed stream, which are often performed in conjunction with producing a liquefied hydrocarbon stream. These 10 installations and line ups need not be further explained herein. In the embodiments described hereinabove, the hydrocarbon well stream separation tank 100, the optional hydrate inhibitor regeneration unit 200, and the 15 hydrocarbon processing means 400 are all located in and/or on an offshore structure. The offshore structure may be a floating offshore structure 500 that floats on a body of water 510 such as the sea. The floating offshore structure 500 may be weathervaningly connected to an 20 anchored turret (not shown), whereby the upstream production conduit 10 suitably enters the floating offshore structure 500 via the turret. The hydrocarbon reservoir 520 in the embodiment of Figure 1 is a subterranean formation 530 below the sea bed 540. 25 Nevertheless, due to the relatively small plot space required to carry out the invention, it is particularly suited for application on an offshore structure, including applications on a floating gas processing structure such as a floating natural gas liquefaction 30 plant. The person skilled in the art will understand that the present invention can be carried out in many various WO 2013/024147 - 1 8 - PCT/EP2012/066064 ways without departing from the scope of the appended claims.

Claims

1. A method of producing a hydrocarbon product stream from a hydrocarbon well stream, comprising the steps of: - producing a hydrocarbon well stream from a subterranean earth formation, said hydrocarbon well stream comprising 5 at least a vaporous hydrocarbon phase and a liquid phase; - feeding the hydrocarbon well stream into a lower compartment of a hydrocarbon well stream separation tank; - in said lower compartment allowing a liquid from the liquid phase to separate from the vaporous hydrocarbon 10 phase; - discharging the liquid from the hydrocarbon well stream separation tank via a liquid discharge outlet; - passing the vaporous hydrocarbon phase to an upper compartment within the hydrocarbon well stream separation 15 tank via an internal passage, wherein the internal passage is located gravitationally higher than the liquid discharge outlet and wherein the upper compartment is located gravitationally above the lower compartment; - passing the vaporous hydrocarbon phase through a filter 20 disposed in the upper compartment of the hydrocarbon well stream separation tank; - accumulating mercury from the vaporous hydrocarbon phase in said filter; - discharging a filtered vaporous hydrocarbon stream from 25 said upper compartment, said filtered vaporous hydrocarbon stream comprising a hydrocarbon molecules containing vapour from the vaporous hydrocarbon phase without the mercury that has accumulated in the filter; - further processing the filtered vaporous hydrocarbon 30 stream to produce a hydrocarbon product stream from said filtered vaporous hydrocarbon stream. WO 2013/024147 - 2 0 - PCT/EP2012/066064

2. The method of claim 1, wherein said filter is a sorption filter comprising a sorbent material capable of sorbing mercury from the vaporous hydrocarbon phase.

3. The method of claim 1 or claim 2, wherein the 5 vaporous hydrocarbon phase is passed from the lower compartment to the filter without a significant pressure loss.

4. The method of any one of the preceding claims, wherein said lower compartment functions as a three-phase 10 separator, wherein said liquid from the liquid phase is separated into a liquid aqueous phase and a liquid hydrocarbon phase that are discharged from the hydrocarbon well stream separation tank separately from each other. 15

5. The method of any one of the preceding claims, wherein said further processing of said filtered vaporous hydrocarbon stream comprises deriching of the filtered vaporous hydrocarbon stream from one or more acid components. 20

6. The method of claim 5, wherein said deriching comprises contacting at least part of the filtered vaporous hydrocarbon stream with an amine solvent.

7. The method of any one of the preceding claims, wherein said filtered vaporous hydrocarbon stream 25 comprises methane and wherein said further processing of said filtered vaporous hydrocarbon stream comprises extracting heat from at least a methane-containing portion of the filtered vaporous hydrocarbon stream to form a liquefied methane-containing stream as the 30 hydrocarbon product stream.

8. A hydrocarbon well stream separation tank comprising: WO 2013/024147 - 21 - PCT/EP2012/066064 - a lower compartment for separating a liquid of a liquid phase from a vaporous hydrocarbon phase of a hydrocarbon well stream; - an inlet for allowing the hydrocarbon well stream to 5 flow from outside of the hydrocarbon well stream separation tank into the lower compartment of the hydrocarbon well stream separation tank; - a liquid discharge outlet for discharging the liquid from the hydrocarbon well stream separation tank; 10 - an upper compartment located gravitationally above the lower compartment; - an internal passage fluidly connecting the lower compartment and the upper compartment, wherein the internal passage is located gravitationally higher than 15 the liquid discharge outlet; - a discharge outlet for discharging a filtered vaporous hydrocarbon stream from the upper compartment to outside of the hydrocarbon well stream separation tank; - a filter, capable of filtering mercury from the 20 vaporous hydrocarbon phase, disposed in the upper compartment wherein the internal passage is fluidly separated from the discharge outlet such that the vaporous hydrocarbon phase must pass through the filter before being discharged from the lower compartment 25 through the discharge outlet.

9. The hydrocarbon well stream separation tank of claim 8, wherein said filter is a sorption filter, comprising a sorbent material capable of sorbing mercury from the vaporous hydrocarbon phase. 30

10. The hydrocarbon well stream separation tank of claim 8 or 9, wherein the internal passage is open such that no significant pressure loss is imparted on the vaporous WO 2013/024147 - 2 2 - PCT/EP2012/066064 hydrocarbon phase as it passes from the lower compartment to the filter.

11. The hydrocarbon well stream separation tank of any one of claims 8 to 10, wherein said lower compartment is 5 a three-phase separator, wherein said liquid from the liquid phase is separated into a liquid aqueous phase and a liquid hydrocarbon phase, which three-phase separator comprises an aqueous phase discharge outlet arranged to selectively discharge the liquid aqueous phase from the 10 hydrocarbon well stream separation tank and a hydrocarbon phase discharge outlet arranged to selectively discharge the liquid hydrocarbon phase from the hydrocarbon well stream separation tank separately from the liquid aqueous phase. 15

12. A system for producing a hydrocarbon product stream from a hydrocarbon well stream, comprising: - the hydrocarbon well stream separation tank of any one of the claims 8 to 11; - hydrocarbon processing means fluidly connected to the 20 discharge outlet of said hydrocarbon well stream separation tank and arranged to receive the filtered vaporous hydrocarbon stream and to produce a hydrocarbon product stream from said filtered vaporous hydrocarbon stream. 25

13. The system of claim 12, wherein said hydrocarbon processing means comprises an acid component removal unit fluidly connected to the discharge outlet of said hydrocarbon well stream separation tank.

14. The system of claim 13, wherein said acid component 30 removal unit comprises an amine solvent unit arranged to contact at least part of the filtered vaporous hydrocarbon stream with an amine solvent. WO 2013/024147 - 23 - PCT/EP2012/066064

15. The system of any one of claims 12 to 14, wherein said hydrocarbon processing means comprises a liquefaction system arranged to extract heat from at least a methane-containing portion of the filtered 5 vaporous hydrocarbon stream to form a liquefied methane containing stream as the hydrocarbon product stream.