AU2013274971A1

AU2013274971A1 - Using wellstream heat exchanger for flow assurance

Info

Publication number: AU2013274971A1
Application number: AU2013274971A
Authority: AU
Inventors: Bianca Maria Mita NOGUEIRA; Kjell Olav Stinessen
Original assignee: Aker Subsea AS
Current assignee: Aker Solutions AS
Priority date: 2012-06-14
Filing date: 2013-06-12
Publication date: 2015-01-22
Anticipated expiration: 2033-06-12
Also published as: AU2013274971B2; BR112014031103A2; NO20120694A1; AU2013274971A2; WO2013187771A1; NO335391B1

Abstract

Method for facilitating transportation of flowable hydrocarbons through an: insulated pipeline comprising passing a flow of hot flowable hydrocarbons (4) through a separator (1) for separation into a gaseous phase (5) and a cold liquid phase (3a). Thereafter, passing the cold liquid phase (3a) through at least one heat exchanger (3) downstream said separator (1). The heat exchanger also receives heat from a flow of hot flowable hydrocarbons (4), whereby the temperature of said cold liquid (3a) is increased to a desired level. The liquid (3b) flowing out from said heat exchanger (3) is transported to the main pipeline for onward transportation. An apparatus for carrying out the method is also disclosed.

Description

WO 2013/187771 PCT/N02013/050104 FIELD OF THE INVENTION The present invention in general, relates to a method and apparatus for flow assurance of flowable hydrocarbons along a pipeline, comprising passing a well stream of flowable hydrocarbons through a separator for separation thereof into 5 a gas phase and a liquid phase. More specifically, the present invention relates to a method and apparatus for flow assurance ensuring flowable hydrocarbons along insulated pipelines, such that precipitation of undesirable substances during fluid hydrocarbon 10 transportation, such as wax deposition and hydrate formation are prevented, More particularly, the present invention relates to a method for flow assurance of flowable hydrocarbons, according to the preamble of claim 1 and to an apparatus therefore, according to the preamble of claim 12, TECHNICAL BACKGROUND OF THE INVENTION In onshore, offshore subsea operations such as for hydrocarbon exploration and production, application of insulated pipelines for fluid transport is common 2i For example subsea processing plants such as subsea compression stations have long export distance to shore and for that purpose, flowable hydrocarbons, that may be a mixture of oil and water, can be transported along insulated pipelines for flow assurance over long distances to avoid temperature drop 25 below an acceptable level if heating of the lines are not used neither chemicals. Main fields requiring such flow assurance for fluid hydrocarbon pipelines include subsea condensate export pipelines, onshore condensate and oil export pipelines located in a cold environment and so on, 30 Formation of undesirable precipitates is a common problem encountered in transportation of such fluid hydrocarbon. Especially, when transporting unrefined or only partially refined products, Obviously, such precipitates cause WO 2013/187771 PCT/N02013/050104 immense hindrance in the flow of fluid hydrocarbon and may lead to reduced flow rates and even clogging of the flowline. The precipitates as referred to in the preceding paragraph may be wax, .5 hydrates, asphaltenes, resins, napthallenes, aliphatic hydrates and so on, as known to persons skilled in the art. In general, there is a risk of formation of undesirable deposits in the flow line, when the temperature of the fluid drops below Wax Appearance Temperature (hereinafter referred to as WAT) or hydrate formation. 10 A multiphase well stream may have a temperature as high as 700 C to 1000 C. or even 1301C, This is much higher than the usual hydrate formation temperature, which is around 20*C and the wax formation temperature, which is around 30"C. If the fluids are transported through non-insulated flow lines, the 15 temperature will drop to close to seawater temperature after 5~10 km. If the flow line is insulated, this temperature drop can be extended to about 50 km. The drop in temperature may result in increased hydrate and wax formation, It is clear that insulation alone can be sufficient only for relatively short 20 distances, Today it is desirable to transport hydrocarbons over a distance up to 100 - 200 km. The most common means for preventing hydrate formation is by the use of hydrate preventing chemicals (and correspondingly to use waxing preventing 25 chemicals). The disadvantage is that use of large amounts of chemicals is necessary, which has a significant cost impact. To reduce the consumption of the most commonly used hydrate preventing chemical, monoethyleneglycol (MEG), regeneration plants are used, witch increases investment costs and adds technical complexity and weight on platforms. Chemicals also pose 30 potential threats to the environment, and equipment for separation and neutralization of chemicals are necessary to achieve the goal of "zero emissions.

WO 2013/187771 3 PCT/N02013/050104 Direct Electric Heating (DEH) to warm up the pipelines for preventing precipitate formation is also an alternative. However, this method is grossly expensive, having regard to the length of pipelines applied. .5 On the other hand, it is also known that cooling of the hot well stream prior to its entry into a separator is beneficial to improve gas and liquid separation, It is also highly beneficial that the gas entering a compressor is cool. That reduces the energy required for compression. However, overcooling causes deposits/precipitates as stated in the preceding paragraph, especially when the 10 products are transported over long distances where the ambient temperature is low. To solve the draw back of the overcooling of the liquid phase, attempts have been made to relocate the inlet cooler to cool down the gas line only, but in that 15 event an additional high efficiency scrubber is needed downstream of this cooler, to separate the remaining liquid phase before entering the compressor. This invites complication in the system and adds on to the cost. Granted US patent 7261810B2 teaches to solve this problem by cooling the hot 20 hydrocarbons to be transported consecutively in a reactor and a heat exchanger, so that the undesirable substances are precipitated in the reactor and the heat exchanger in that order. Thereafter, the hydrocarbons are transported, supposedly free of precipitating solids. However, this technique does not sufficiently prevent precipitate formation over substantially long 25 distances, and safe transport can not be achieved in its entirety by this method of coolig Furthermore, the above method requires a source of cold fluid containing small crystals for its addition to the hot fluid hydrocarbon and the basic principle is 30 mixing of the hot fluid hydrocarbon with this cold fluid for lowering the temperature of the fluid hydrocarbon to be transported, for precipitation of unwanted substances. The crystals in the cold fluid act as nucleation points for WO 2013/187771 4 PCT/N02013/050104 precipitation of similar substances from the hot fluid. Hence, the method is cumbersome as well and can not be entirely relied upon. Addition of chemicals for delaying or preventing formation of precipitates is 5 another techrnque but this apart from being costly, has been not found to be technically sufficient for preventing precipitate formation during transportation over long distances. The chemicals will also have to be separated from the products after the transport. 10 Accordingly, there is a long felt need for developing a method and apparatus for flow assurance of fluid hydrocarbon along a network of insulated pipelines in a technically reliable and cost effective manner, whereby the disadvantages of prior art as contemplated above, are substantially minimized or eliminated. 15 The present invention meets this aforesaid long felt need and other needs associated therewith. OBJECTS OF THE INVENTION 20 It is the principal object of the present invention to provide a method and apparatus for flow assurance of flowable hydrocarbons along a, preferably insulated, pipeline in a technically reliable and cost effective manner by utilization of the heat content of the well stream upstream a subsea processing plant e.g. a compression station or excessive heat from equipment of the 25 station, such as gas compression, whereby the disadvantages of prior art are substantially minimized or eliminated. It is another object of the present invention to provide a method and apparatus for flow assurance of flowable hydrocarbons along a, preferably insulated, 30 pipeline, such that formation of undesirable precipitates during transportation over substantially long distances is prevented, WO 2013/187771 PCT/N02013/050104 It is another object of the present invention to provide a method and apparatus for flow assurance of flowable hydrocarbons along a, preferably insulated, which is simple and does not involve compcated steps or components, 5 A further object of the present invention is to provide a method and apparatus for flow assurance of flowable hydrocarbons along, preferably insulated, pipelines by effecting heat exchange between hot flowable hydrocarbons from a well stream and flowable hydrocarbons to be transported, so that the temperature of the flowable hydrocarbons to be transported is increased to a 10 desired level for preventing formation of undesirable precipitates. The general principle of the present invention is to use heat from the well stream upstream of a subsea processing plant and possibly also heat generated by equipment in the plant, especially compressors, to prevent 15 formation of hydrates, precipitation of wax and precipitation of other components, by transferring this heat from the well stream and/or said heat generating component to the fluids by indirect heat exchange and thereby using this heat to keep the temperature sufficiently high 20 More specifically the invention relates to flow assurance by utilization of heat from a well stream upstream of a cooler and a separator and possibly also heat generated by equipment, such as by compressing gas, in a subsea processing system, and heat exchange of mentioned heat with liquid pipelines downstream the process separator Flow assurance is achieved by warming up the outlet 25 liquid line of the separator to above hydrate formation temperature, wax appearance temperature (cloud point), and above precipitation temperature of other components (e. g. asphaltenes) that can clog the flow by accumulation below certain temperatures, 30 To keep the temperature above problematic level in long transport lines along the seabed with its low temperature, it will normally be necessary to insulate the lines. The described method of utilizing excess heat in combination with insulated fluid transport lines can be a much cheaper solution than electric WO 2013/187771 6 PCT/N02013/050104 heating of said lines or use of chemicals. Even if this method should not ensure flow assurance alone the whole length of long lines, or during some modes of operation (e g, low flow) or shutdown, it can signcantly reduce the need for heating or chemicals for instance to only inject chemicals or switch on electric .5 heating at shutdown. How the foregoing objects are achieved and some other advantageous features, still not disclosed in prior art, will be clear from the following non limiting description. 10 All through the specification, including the claims, the words "pipeline", Towable hydrocarbons" "cold fluid" "separator", "inlet cooler", "heat exchanger" "onshore", "offshore"; "hot well stream", and "hot flowable hydrocarbons" are to be interpreted in the broadest sense of the respective terms and includes all 15 similar items in the field known by other terms, as may be clear to persons skilled in the art. Restriction/limitation, if any, referred to in the specification., s solely by way of example and understanding the present invention, SUMMARY OF THE INVENTION 20 According to a first aspect of the present invention there is provided a method for flow assurance of flowable hydrocarbons along a pipeline, preferably an insulated pipeline comprising exchanging heat between a flow of hot flowable hydrocarbons or hot well stream and the fluids to be transported. The hot well 25 stream flows into a separator. The separator separates the well stream into a gaseous phase and a liquid phase. In order to faciltate the gasliquid separation, the well stream is cooled by an inlet cooler located upstream the separator, 30 According to the method of the present invention, the liquid phase is thereafter passed through at least one heat exchanger, located downstream of the separator, The heat exchanger has a constant flow of hot well stream, This ensures that the temperature of the cold liquid from the separator is increased WO 2013/187771 7 PCT/N02013/050104 to a desired level and finally the liquid flowing out from the heat exchanger is transported to the main pipeline, for onward transportation. More preferably, the hydrocarbons of the well stream exiting from the heat 5 exchanger is recycled back to the well stream line or preferably to the ine downstream an inlet cooler, through which the hot flowable well stream passes, before entering the separator, According to the present invention there is also provided an apparatus for 10 carrying out the method. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES Having described the main features of the invention above, a more detailed and 15 non-limiting description of some preferred embodiments will be given in the following with reference to the drawings, in which: Figure 1 is a schematic line drawing of a preferred embodiment of the apparatus according to the present invention and also illustrates how the 20 apparatus is applied to run the process of the present invention. Figures 2 and 3 illustrate line drawings of two more preferred embodiments of a part of the apparatus according to the present invention and also illustrate how those apparatuses are applied to run the process of the present invention, 25 Figure 4 illustrate the present invention when using heat generated by equipment, in this example a compressor, Figure 5 ilustrates a further alternative embodiment of the invention, were 30 separated gas is used as a heating medium, WO 2013/187771 s PCT/N02013/050104 Figure 6 illustrates yet another embodiment where the well stream heats seawater that is stored in a tank and subsequently used to heat the liquid condensate. .5 DETAILED DESCRIPTION OF THE INVENTION The following provides a detailed non-liniting description of some preferred embodiments of the present invention which are purely exemplary. 10 Hot well stream referred to hereinbefore and hereinafter may come from one or more drilling hole well(s) or through a transport line from a nearby oil or gas field, as known to persons skilled in the art. Further, hereinbefore and hereinafter for the sake of explanation and simplicity, only hot well stream is referred to. It is to be understood that such term also embraces, hot flowable 15 hydrocarbons, such as from a hydrocarbon process plant or similar, which may be at an elevated pressure. Further, due to similar reasons, precipitates have been referred to as wax and hydrates., It includes other precipitates as known in the field as well and as 20 explained under the heading "Technical Background of the Invention", Now referring to the accompanying figure 1, a preferred embodiment of the invention will be explained in detail. A hot well stream flows along the line 4. The fine 4 is branched into a first fine 4a', which extends through an inlet cooler 25 2 and enters the separator I along line 4. This hot well stream prior to entering inlet cooler 2, is at an elevated temperature. The inet cooler may be of the type described in the applicant's Norwegian patent application NO 2011 0946, which is hereby incorporated by reference. 30 The inlet cooler 2 is preferably applied to bring down the temperature of hot well stream for ensuring condensation of the liquid fraction of the hydrocarbons, so that the gas and liquid fractions may be separated. In the separator 1, the hot well stream separates into dry gas 5 (the gas 5 should be as dry as possible in WO 2013/187771 9 PCT/N02013/050104 order for it to be efficiently compressed by a compressor in a later stage) and cold liquid 3a. The liquid may be gas condensate, oil and/or water. The liquid may also contain small proportions of gas, This cold liquid is to be transported along the export pipelines The cold liquid 3a which leaves the separator I is allowed to enter a heat exchanger 3, This heat exchanger 3 is located downstream the separator 1, along a pipeline. 10 From the hot well stream is also branched off a second line 4a which leads to the heat exchanger 3 located downstream the separator 1. In the heat exchanger 3 the hot well stream exchanges heat with the cold liquid from the separator 1 in order to increase the temperature of the cold liquid. At the same time the temperature of the well stream through the heat exchanger 3 ils 15 reduced, The heat exchanger 3 may be configured so as to be co-current or counter current and this is not consequential to the present invention. The dry gas 5 may be transported separately, which is not shown in detail, 20 The heat exchanger 3 is preferably having a constant feed of hot well stream along line 4a. So, when the cold fluid enters the heat exchanger 3, it finds the hot fluid hot well stream there. Consequently, heat exchange takes place between the hot well stream and the cold fluid. Alternatively the line 4a may 25 have a valve (not shown) that can be adjusted to provide the exchanger 3 with a flow of hot fluid adapted to the heating requirements to bring the temperature of the liquid from the separator 1 to the optimal level. Although only one heat exchanger 3 is shown, there may be a plurality of such 30 heat exchangers located downstream of the separator, all having constant feed of hot well stream in the same manner, Further, there may be a plurality of separators I as well and all function in the same manner, WO 2013/187771 10 PCT/N02013/050104 The temperature of the cold fluid is thus increased to a desired level, Hence, the liquid 3b which exits the heat exchanger 3 has a desired temperature as exemplified hereinafter, which prevents formation of wax or hydrate or other precipitates, This liquid 3b is now transported to the main pipeline for onward .5 transportation (not shown in detailY The well stream which leaves the heat exchanger 3 along the line 4b has a lower temperature, as compared to the hot well stream 4 which enters the inlet cooler 2 along 4a'. The temperature may be comparable to the well stream 10 which enters the separator 1 along line 4'. As shown in the figure 1, preferably, the well stream which leaves the heat exchanger 3 along line 4b is re-circulated back to the separator 1 by connecting the line 4b to line 4" downstream of the inlet cooler 2. Alternatively, depending 15 on the temperature, this well stream flowing through line 4b may be mixed with the hot well stream 4 at line 4a', Figures 2 and 3 illustrate two alternative embodiments where the heat exchanger 3 is integral with the separator I but in any event is located 20 downstream to it. Here, the like reference numerals represent like features and the functioning is also essentially the same, as will be appreciated by persons skilled in the art. Figure 4 illustrate possible enhancement to the present invention, It illustrate a 25 well stream 4 that is led through an inlet cooler 2 and enters a separator I along a line 4". From the separator 1 the gas exits through a gas line 5 to a compressor 6, The gas exists the compressor 6 through a compressed gas line 6' The liquid exists the separator I through a liquid line 3a and is further through a heat exchanger 3 After the heat exchanger theliquid enters a liquid 30 transport line 3b, A part of the compressed gas is branched off from the line 6' to a branch line 6a and is led through the heat exchanger 3 After the heat exchanger 3 the gas WO 2013/187771 ' 1 PCT/N02013/050104 enters a further gas line 6b. This is described as a separate invention in a co pending application to the present, However, this arrangement may also be used to enhance the present invention to ensure sufficient heat availability. > As will be understood from the above, instead of branching off a part of the well flow, as per the embodiment of figure 1, in the alternative embodiment of figure 4, a part of the compressed gas that has been heated during the compression in the compressor (6) s branched off from the hot discharge line 6' to the branch line 6a and used to heat up the liquid that enters the heat exchanger 10 from the line 3a. The gas in the line 6b may be led back to the line 6' or to the well stream line 4 depending on the chosen process strategy. The present invention thus proposes system configurations to allow heat transfer between the hot well stream and the cold liquid, preferably condensate 1$ or oil-water stream. The heat transfer takes place in a heat exchanger 3 where the wellI stream 4 or the compressed gas is the hot fluid and flows into the heat exchanger 3 along the line 4a or 6a, respectively, The cold liquid 3a also flows into the heat 20 exchanger 3, The well stream or gas flows out of the heat exchanger along line 4b or line 6b, with lower temperature than its inlet temperature and the liquid 3b flows out with higher temperature than its inlet temperature. For all configurations of the apparatus according to the present invention, the 25 well stream return along line 4b may be directed into the inlet well stream 4 upstream or downstream of the inlet cooler 2 along line 4% or in the alternative, the gas may be returned from the line 6b to the compressed gas line 6', the uncompressed gas line 5 or the well stream at line 4 or line 4% This depends on the return temperature desired or other process strategies. 30 Pressure drop is ensured for the circulation of the well stream along line 4b. An existing pressure drop may be used, as injecting the well stream return line 4b downstream the inlet cooler 2. If that is not enough, an additional pressure drop WO 2013/187771 1 PCT/N02013/050104 is created Mn tlhe system by miears known per se to the person of skill Tihe same appfes for the gas in Wie 6&b, depending on where it s resumed, Thus, the present Invention: with standard pipeflne insulaStion makes it 5 possible to export gas andor condensate through ng , pne' s withA sufficient operatn temperature to avoid formation of unwanted precpi4tates during transportation over substatnti-ay long dstames, The idea operating tepeature is dependent on the length of the pipe - :ndNN heat -ost per ut length during transit. 10 The present invention achieves it goal of subtantil precpitate free transCportaton of hydrocaro for subs tatialylong distances along a pipelie, b~y applying fficient exchange of heat between the flowabte hydrocarbons to be transported and the hot vvel stream. The e Ixenplary table below shows some results for a subsea processing and compression station case wh'er the condensate WAT (x pern T mperature) is 34'C. The condensate export line is of 8" diameter and mome than 100 km length The seawater temperature conStdared to CalculatS the heat 20 toss on the pipehne 5s C , Table 1: Condensate pipeine enhat above WAT . ................ ......................... ......................................... ........ ..... :... .Y s ................... ' ........................................ . ~..... 25 The table 1 snhows that, e g,: f 15%b of the hot welstreamn (k10C mass flow.' exchanges- heat with the condensate ine, the initial condensate export temertue il be 92*C insead of 156C. S, the codnaepipelieoeae above WAT codition for a substantial length of the export pipeline. Ths is 30 perfectly chvbeasthe odeatms fklow i-s ;aro und 10% of hetoal gas mass fPow, WO 2013/187771 13 PCT/N02013/050104 If the calculated heat loss of the transported hydrocarbons is great enough to bring the temperature below the WAT, it is possible to equip the last portion of the transportation line with DEH in order to keep the temperature high enough 5 throughout the transportation distance. The need for DEH will, however, be substantially less than without the present invention. From the foregoing description and also from the appended claims it would be clear to persons skilled in the art, that all the objectives of the present invention 10 are achieved. The present invention is applicable in respect of all types of transportation of flowable hydrocarbons along network of pipelines as clarified before The present invention has been described with reference to preferred 15 embodiments and drawings for the sake of understanding only and it should be clear to persons skilled in the art that the present invention includes all legitimate modifications within the ambit of what has been described hereinbefore and claimed in the appended claims. 20 Figure 5 shows a further alternative embodiment of the present invention. where the hot gas is used for heating the liquid. The figure shows, the well flow 4 entenng a first separator 1a without first being led through an :inlet cooler. The well flow is separated into a predominantly liquid phase 3a and predominantly gas phase 5, However, the gas phase 5 does have a fair amount of residual 25 liquid. The gas is led through an inlet cooler 2 before entering a second separator 1b where the remaining liquid is removed from the gas and exited through a liquid ine 3c. The predominantly dry gas is led through a gas line 5c to a compressor 6, 30 Before the gas 5 with residual liquid enters the inlet cooler 2, some of the gas is branched off to a line 5a and led through a heat exchanger 3, where heat from the gas is transferred to the liquid 3c exiting from the separator 2, The thus WO 2013/187771 '4 PCT/N02013/050104 heated liquid is led to the liquid line 3a through a line 3b, while the now cooled gas 5b is led to the inlet of the separator 1 b, Figure 6 shows a yet further embodiment of the invention where the hot well .5 stream is used to heat seawater, which in turn is used to heat the liquid condensate. The well flow 4 is led through an inlet cooler 2 and then to a separator 1, where it is separated into a gas phase 5 and a liquid phase 3a. Seawater 7 is drawn into the inlet cooler 2 and receives heat from the hot well 10 flow 4. The hot seawater 7a is transferred to a storage tank 8. From this tank hot seawater is drawn through a line 7b to a heat exchanger 3 and used to heat the liquid phase 3a. The now cooled seawater 7c that exits the heat exchanger 3 may be transported to shore or expelled to the surrounding waters, depending on the environmental regulations. The heater liquid 3b is transported to shore. 15 This embodiment is suitable for situations were the heating requirements are varying. Since hot seawater is stored in the tank 8, more water can be drawn from the tank when the liquid production from the separator I is high. When the liquid production is low, ie more gas is produced; seawater will be 20 accumulated in the tank 8. In this case a heat exchanger may be used as described in the applicant's Norwegian patent application NO 2011 0946, which is hereby incorporated by reference. The coolers described in Norwegian patents 173890 and 321304 or 25 in Norwegian patent application 20091914 may also be used. These are also incorporated herein by reference. Other combinations of the embodiments described and variations of the embodiments are also possible, within the common knowledge of the person of 30 skill

Claims

1. Method for flow assurance of flowable hydrocarbons along a pipeline 5 comprising letting a stream of hot flowable hydrocarbons (4) flow through a separator (1) for separation thereof into a gas phase (5) and a liquid phase (3a), c h a r a c t e r i s e d i n that heat from the hot flowable hydrocarbons is extracted before the hot flowable hydrocarbons enters the separator (1) and transferred to the quid phase exiting the separator. 10

2. Method according to claim 1, c h a r a c t e r ii s e d i n that the hot well stream of flowable hydrocarbons (4) is fed through an inlet cooler (2) prior to entering said separator (1). 3S. Method according to claim 2, c h a r a c t e r ii s e d i n that at :least a part of the hot well stream of flowable hydrocarbons (4a) is branched off prior to entering the inlet cooler (2) and is led to the at least one heat exchanger (3) to 20 heat the liquid phase.

4. The method according to claim 2 or 3, c h a r a c t e r i s e d i n that the flowable hydrocarbons (4b) exiting said heat exchanger (3) is recycled back to 25 downstream the separator (4a, 4), upstream or downstream said inlet cooler(2),

5. The method of claim 1, c h a r a c t e r i s e d i n that at least a part of the 30 gas phase from the separator (Ia) is led to the heat exchanger (3) to heat the liquid phase, WO 2013/187771 16 PCT/N02013/050104

6. The method of claim 5, c h a r a c t e r i s e d i n that the gas phase is compressed, whereby the gas is heated by the compression, and that at least a part of the compressed gas (6a) is led to the heat exchanger (3) to heat the 5 liquid phase. 7, The method of claim 5 or 6, c h a r a c t e r i s e d i n that the gas (6b) exiting the heat exchanger (3) is recycled back to the well stream (4, 4) 10 upstream of the separator (1) or the gas phase (5, 6) upstream or downstream of the compression stage (6) a. The method of claim 1 c h a r a c t e r i s e d i n that a coolant is||ed 15 through a heat exchanger (2) to be heated by the well stream (4) and that the heated coolant is used for heating the liquid from the separator (1). 9 The method of claim 8, c h a r a c t e r s e d i n that the heated coolant is 20 stored in a tank (8) prior to being used to heat the liquid

10. The method of claim 8 or 9, c h a r a c t e r i s e d i n that the coolant is seawater, which is drawn from the surrounding sea and expelRed to the sea 25 after use.

11. The method according to any of the claims I to 10, c h a r a c t e r i s ed i n that said liquid (3.) is a fluid condensate such as odi and/or natural gas or oi 30 water. WO 2013/187771 17 PCT/N02013/050104

12. An apparatus for flow assurance of flowable hydrocarbons, comprising at least one insulated pipeline (3b), a separator (1) for separating hot flowable hydrocarbons (4) into a gas phase (5) and a liquid phase (3a), 5 h a r a c t e r i s e d i n that there is provided at least one heat exchanger (3) located downstream said separator (1) for receiving inflow of the liquid phase (3a) and adapted to receive hot flowable hydrocarbons (4, 6a) or hot seawater, for transferring heat to increase the temperature of said liquid phase (3a) to a desired level by heat exchange. 10

13. The apparatus according to claim 12, c h a r a c t e r i s e d i n that said heat exchanger (3) is integral with said separator (1), 15 14. The apparatus according to any of claims 12 or 13, c h a r a c t e r i s e d i n that said heat exchanger (3) is a counter current heat exchanger. 15, 20 The apparatus according to any of claims 12 or 13, c h a r a c t e r is e d i n that said heat exchanger (3) is a co-current heat exchanger.

16. The apparatus according to any of claims 12 to 13, c h a r a c t e r i sa e d i n 25 that said heat exchanging in heat exchanger (3) is via forced convection.

17. The apparatus according to any of claims 11 to 13, c h a r a c t e r i s ed i n that said heat exchanging in heat exchanger (3) is via natural convection. 30