Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
  • F17D1/00—Pipe-line systems
  • F17D1/08—Pipe-line systems for liquids or viscous products
  • F17D1/16—Facilitating the conveyance of liquids or effecting the conveyance of viscous products by modification of their viscosity
  • F17D1/18—Facilitating the conveyance of liquids or effecting the conveyance of viscous products by modification of their viscosity by heating
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
  • E21B43/34—Arrangements for separating materials produced by the well
  • E21B43/36—Underwater separating arrangements
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
  • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
  • C10L3/10—Working-up natural gas or synthetic natural gas
  • C10L3/107—Limiting or prohibiting hydrate formation
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
  • E21B43/34—Arrangements for separating materials produced by the well
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
  • F17D3/00—Arrangements for supervising or controlling working operations
  • F17D3/01—Arrangements for supervising or controlling working operations for controlling, signalling, or supervising the conveyance of a product

Definitions

• 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 a gas phase and a liquid phase.
• 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
• 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 9.
• 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 oii and water, can be transported along insulated pipelines for flow assurance over long distances to avoid temperature drop 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 oii export pipelines located in a cold environment and so on.
• the precipitates as referred to in the preceding paragraph may be wax,
• WAT Wax Appearance Temperature
• a multiphase well stream may have a temperature as high as 70° C to 100" C. or even 130 C C. This is much higher than the usual hydrate formation
• the most common means for preventing hydrate formation is by the use of hydrate preventing chemicals (and correspondingly to use waxing preventing chemicals).
• the disadvantage is that use of large amounts of chemicals is necessary, which has a significant cost impact.
• Granted US patent 72:61810B2 teaches to solve this problem by cooling the hot hydrocarbons to be transported consecutivel 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.
• this technique does not sufficiently prevent precipitate formation over substantially long distances, and safe transport can not be achieved in its entirety b this method of cooi g.
• 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 mixing of the hot fluid hydrocarbon with this cold fluid for lowering the
• a further object of the present invention is to provide a method and apparatus for flo assurance of flowable hydrocarbons along insulated pipelines by effecting heat exchange between compressed gas and fiowable hydrocarbons to be transported, so that the temperature of the fiowable hydrocarbons to be transported is increased to a desired level for preventing formation of undesirable precipitates.
• the general principle of the present invention is to use heat generated by equipment in the plant, especially, compressors, to prevent formation of hydrates, precipitation of wax and precipitation of other components, by transferring this heat from the heat generating component to the fluids by indirect heal exchange and thereby using this heat to keep the temperature sufficiently high.
• the invention relates to flow assurance b utilization of heat generated by equipment, such as by compressing gas, in a subsea processing system, arid heat exchange of mentioned heat with liquid pipelines downstream the process separator.
• Flow assurance is achieved by warming up the outset liquid fine 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 How by accumulation below certain temperatures.
• 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 stream flows into a separator.
• the separator separates the well stream into a gaseous phase and a liquid phase.
• gas-liquid phase In order to facilitate the gas-liquid
• the well stream is cooled by an inlet cooler located upstream the separator.
• 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 compressed gas, This ensures that the temperature of the cold liquid fmm the separator is increased to a desired level and finally the li uid flowing out from the heat exchanger is transported to the main pipeline, for onward transportation.
• the gas exiting from the heat exchanger as recycled back to the well stream line upstream of the separator or more preferably to the gas fine upstream or ⁇ downstream the compressor.
• Figure 1 illustrate the present invention where heat generated by a compressor is utilized.
• Figures 2 and 3 illustrate line drawings of two preferred embodiments of a part of the apparatus according to the present invention and also illustrate how those apparatuses ar applied to run the process of the present invention..
• Hot well stream referred to hereinbefore and hereinafter may come from one or more drilling hole we!i(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 ftowab!e hydrocarbons, such as from a hydrocarbon: process plant or similar, which may be at an elevated pressure.
• FIG. 1 t a preferred embodiment of the invention will be explained in detail, It illustrate a well stream 4 that is led through an inlet cooler 2 and enters a separator 1 along a Sine 4 ⁇ From the separator 1 the gas exits through a gas tine 5 to a compressor 6, The gas exists the compressor 6 through a compressed gas line 6 ? . The liquid exists the separato 1 through a liquid line 3a and is further through a heat exchanger 3. After the heat exchanger the liq id enters a li uid transport line 3b,
• the Inlet cooler may he of the type described In the applicant's Norwegian patent application NO 201 0946, which is hereby incorporated by reference.
• Th 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.
• the hot well stream separates into dry gas 5 (the gas 5 should be as dr as possible in 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 1 is allowed to enter a heat exchanger 3.
• This heat exchanger 3 is located downstream the separator 1, along a pipeline. A part of the compressed gas is branched off from the line 6' to a branch line 8a and is ted through the heat exchanger 3. After the heat exchanger 3 the gas enters a further gas fin ⁇ 6b.
• 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 6 that is not branched off to the heat exchanger 3 ⁇ may be transported separately,
• the heat exchanger 3 is preferably havsng a constant feed of hot gas. So, when the cold fluid enters the heat exchanger 3, it finds the hot gas there.
• the line 8a may have a valve (not shown) that can be adjusted to provide the exchanger 3 with a flow of hot gas adapted to the heating requirements to bring the temperature of the liquid from the separator 1 to the optimal level.
• heat exchanger 3 Although only one heat exchanger 3 is shown, there may e a lurality of such 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 1 as wail and ail function in the same manner.
• the temperature of the cold fluid is thus increased to a desired level.
• 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 transportation (not shown in. ⁇ detail).
• the gas which leaves the heat exchanger 3 along the line 6b has a lower temperature,, as compared to the hot gas 8 ⁇ .
• the temperature may be
• the gas which leaves the heat exchanger 3 along fine 8b may be re-clreuiated back to the compressor 5 or to the gas Ine 6 ! downstream of the branch line 8a, Alternatively, it may be circulated back to the separator 1 b connecting the line 8b to line 4' downstream of the tniet cooler 2. Further alternatively, this gas flowing through line 6b may be mixed with the hot well stream 4 at ins 4a : , This depends on the return tampemium desired or other process strategies.
• the present invention thus proposes system configurations to allow heat transfer between the hot gas and the cold liquid, preferably condensate or oil- water stream ,
• the heat transfer takes place in a heat exchanger 3 where the compressed gas is the hot fluid and flows into the heat exchanger 3 along the line 6a.
• the cold liquid 3a also flows into the heat exchanger 3,
• the gas flows out of the heat exchanger along line 6b, with tower temperature than Its Inlet temperature and the liquid 3b flows out with higher temperature than its inlet temperature,
• Pressure drop is ensured for the circulation of the gas along line 6b.
• An existing pressure drop may he used, as Injecting the gas line 6b downstream the inlet cooler 2. If that is not enough, an additional pressure drop is created in the system by means known per se to the person of skill
• the present invention combined with standard pipeline Insulation makes it possible to export gas and/or condensate through long pipelines with sufficient operating temperature to avoid formation of unwanted precipitates during transportation over substantially long distances.
• temperature is dependent on the length of the pipeline and heat lost per unit length during transit.
• the present invention achieves Its goal of substantially precipitate free transportation of hydrocarbon for substantially long distances along a pipeline, by applying efficient exchange of heat between the fiowable hydrocarbons to be transported and the hot well stream.
• the exemplary table 1 below shows some results for a subsea processing and compression station ease where the condensate WAT (Wax Appearance Temperature) is 34*C.
• the condensate export f ns is of 8* diameter and more than 100 km length.
• the seawater iemperature considered to calculate the heat loss on the pipeline is S'C.
• the table 1 shows that, e,g,, If 15% of the hot well stream (1 QQX) mass flow exchanges heat with the condensate line, the initial condensate export temperature witi be B2°C instead of 15°C, So, the condensate pipeline operates above WAT condition for a substantial length of the export pipeline. This is perfectly achievable as the condensate mass flow is around 0% of the total gas mass flow, 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 throughout the transportation distance. The need for DEH will, however, be substantially less than without the present invention.
• An alternative embodiment of the invention is to use seawater to transfer the heat from the hot gas to the li uid condensate.
• a heat exchanger against sea water is inserted in the line 6' and the sea water is thereafter used to heat the liquid fiowtng through the eat exchanger 3,
• a storage tank for hot seawater may be situated in the seawater tine between the heat exchanger with the hot gas and the heat exchanger with the coid liquid. From this tank hot seawater can be drawn to the heat exchanger 3 and used to heat the liquid phase 3a.
• the now cooled seawater that exits the heat exchanger 3 may be transported to shore or expelled to the surrounding waters,, depending on the environmental regulations,
• This embodiment is especially- suitable for situations were the heating requirements are varying. If hot seawater is stored in the t nk, more water can be drawn from the tank when the liquid production from the separator is high. When the liquid production is low, i.e. more gas is produced; seawater will be accumulated in the tank.
• a heat exchanger may be used as described in the applicant's Norwegian patent application NO 201 1 0946, which is hereby incorporated by reference.
• the coolers described in Norwegian patents 173890 and 321304 or in Norwegian patent appiication 20091914 may also be used. These are also incorporated herein. y reference.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Health & Medical Sciences (AREA)
• Water Supply & Treatment (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Public Health (AREA)
• Organic Chemistry (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Pipeline Systems (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)
• Separation By Low-Temperature Treatments (AREA)

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Citations (5)

• 2012
  • 2012-06-14 NO NO20120695A patent/NO335390B1/no not_active IP Right Cessation
• 2013
  • 2013-06-12 WO PCT/NO2013/050106 patent/WO2013187773A1/en active Application Filing
  • 2013-06-12 BR BR112014030960A patent/BR112014030960A2/pt not_active IP Right Cessation
  • 2013-06-12 AU AU2013274973A patent/AU2013274973B2/en not_active Ceased

Patent Citations (5)

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