GB2483039A

GB2483039A - Method for treating hydrocarbons

Info

Publication number: GB2483039A
Application number: GB1121967.2A
Authority: GB
Inventors: Van-Khoi Vu; Hung-Minh Dang
Original assignee: Total SE
Current assignee: TotalEnergies SE
Priority date: 2009-06-26
Filing date: 2010-06-25
Publication date: 2012-02-22
Anticipated expiration: 2030-06-25
Also published as: FR2947281A1; GB201121967D0; FR2947281B1; WO2010150234A2; NO20120010A1; WO2010150234A3; GB2483039B

Abstract

The invention relates to a method for treating hydrocarbons, said method including: providing an initial hydrocarbon stream including water; adding a liquid solvent into the initial hydrocarbon stream so as to provide an intermediate hydrocarbon stream, said liquid solvent containing a weight proportion of C3-C6 alkanes that is greater than or equal to 80%; gravitationally separating the intermediate hydrocarbon stream into an oleic phase and an aqueous phase; decompressing the oleic phase and separating the oleic phase into a gaseous hydrocarbon phase and a liquid hydrocarbon phase; recycling the gaseous hydrocarbon phase so as to at least partially provide the liquid solvent; and retrieving the liquid hydrocarbon phase. The invention also relates to a facility suitable for implementing said method.

Description

METHOD FOR TREATING HYDROCARBONS

FIELD OF THE Th4VENTION

The present invention relates to a method for treating hydrocarbons, in particular aiming at reducing the water content of a stream of hydrocarbons, as well as to an installation suitable for implementing this method.

TECIThICAL BACKGROUND

Hydrocarbons extracted from reservoirs (called production crudes) generally have to be treated before being stored and/or transported towards refineries where they are upgraded. One of the main treatments consists of removing production water which is mixed with the hydrocarbons. This treatment is generally carried out with separation by gravity, optionally completed with electrostatic coalescence.

When the extracted hydrocarbons have high density and high viscosity (heavy or extra-heavy oils), the hydrocarbons have further to be treated in an upgrading unit (or "upgrader") upstream from the refining, strictly speaking, since standard refineries are designed for mainly treating lighter crude oil. The upgrading produces a light synthetic oil, which may then be transferred to refining.

It is known that by mixing the heavy oils with a hydrocarbon solvent (lighter than heavy oil) it is possible to obtain a diluted heavy crude with a high API degree as well as lesser viscosity. Thus, the conveying of the heavy oils from the production site to the upgrading unit is facilitated by fluidifying them with the solvent.

As a hydrocarbon solvent, naphtha is generally used, which is a hydrocarbon cut mainly comprising C6-C20 hydrocarbons. With this solvent it is possible to increase the AN degree of the hydrocarbons to be treated, typically up to a value of about 20 at most (in the case of heavy oils). The solvent is generally recycled by a distillation method at the upgrading unit, and then brought back to the production site in a conduit in the opposite direction to the main conduit transporting the produced hydrocarbons.

Naphtha is used for its good compatibility with heavy oils, with which it is possible to have a homogeneous mixture, and in order to avoid risks of biphasic separation or creation of deposits during the transport to the upgrading unit.

Removal of the water mixed with the hydrocarbons also poses particular problems in the case of heavy oils. It is actually essential to separate the oil and the water, since oil/water (either oil-in-water or water-in-oil) emulsions tend to be very stable. Oil/water separation is conventionally accomplished by gravitational separation. Tndeed, according to Stokes' law, the settling rate of a water particle in an oleic phase is proportional to the specific gravity difference between the oleic phase and the water, and is inversely proportional to the viscosity of the oleic phase.

Therefore, when the oleic phase has high viscosity and high density (therefore a density close to that of water), settling of the water is very poorly accomplished.

In order to improve the separation of water, it is possible to increase the size of the separators or to increase the temperature at which separation is carried out in order to reduce the viscosity of the oleic phase, which has a high cost and poses considerable practical problems. Mixing the production crude with the hydrocarbon solvent (naphtha) was also suggested before the gravitational separation step.

However, this step typically allows an increase in the API degree of the hydrocarbons up to a value of about 20 at most, which remains insufficient for simplifying the oil/water separation in a totally satisfactory way (the size of the separators notably remaining very large).

Moreover, document WO 99/19425 describes a method for upgrading heavy oils which is more particularly intended for hydrocarbons recovered from mining residues, containing a high solid content. A hydrocarbon solvent is added to the heavy oils. The separation of water as such is partly carried out by means of flash decompression of the mixture of heavy oils and of the hydrocarbon solvent (consisting of vaporizing part of the hydrocarbons and of the water) and in addition by means of a hydrocyclone. This scheme is based on the precipitation of certain hydrocarbon compounds by means of the solvents used. This is a very complex scheme.

Therefore, there exists a need for a method for treating hydrocarbons which gives the possibility of carrying out an oil/water separation more efficiently, more simply, more economically and more rapidly than in the existent methods, in particular for heavy oils.

SUMMARY OF THE INVENTION

The invention firstly relates to a method for treating hydrocarbons, said method comprising: -providing an initial stream of hydrocarbons comprising water; -adding a liquid solvent into the initial stream of hydrocarbons in order to provide an intermediate stream of hydrocarbons, said liquid solvent comprising a mass proportion of C3-C6 alkanes of more than or equal to 80%; -separating by gravity the intermediate stream of hydrocarbons into an oleic phase and an aqueous phase; -decompressing the oleic phase and separating the oleic phase into a gaseous phase of hydrocarbon and a liquid hydrocarbon phase; -recycling the gaseous hydrocarbon phase in order to provide at least partly the liquid solvent; and -recovering the liquid hydrocarbon phases.

According to an embodiment, the initial stream of hydrocarbons has an APT degree comprised between 5 and 25 and the intermediate stream of hydrocarbons has an API degree greater than or equal to 30, preferably greater than or equal to 35, most preferably greater than or equal to 40.

According to an embodiment, the liquid solvent comprises a mass proportion of C3-C4 alkanes greater than or equal to 80%, preferably greater than or equal to 85%, most preferably greater than or equal to 90%, ideally greater than or equal to 95%.

According to an embodiment, the recycling of the gaseous hydrocarbon phase in order to provide at least partly the liquid solvent comprises compression of the gaseous hydrocarbon phase and optionally a supplement of liquid solvent.

According to an embodiment, the step for providing the initial stream of hydrocarbons comprises: -extracting hydrocarbons from an underground formation; -optionally degassing the extracted hydrocarbons; and -optionally removing the solid materials mixed with the extracted hydrocarbons.

According to an embodiment, the initial stream of hydrocarbons comprises less than 20,000 ppm of solid materials, preferably less than 10,000 ppm of solid materials, most particularly less than 5,000 ppm of solid materials, in a mass proportion.

According to an embodiment: -separation by gravity of the intermediate stream of hydrocarbons is carried out at a pressure comprised between 3 and 15 bars, preferably between 5 and 10 bars; and/or -separation of the oleic phase into the gaseous hydrocarbon phase and into the liquid hydrocarbon phase is carried out at a pressure comprised between 1 and 3 bars, preferably between 1 and 2 bars.

According to an embodiment, the aforementioned method further comprises: -transporting the liquid hydrocarbon phase followed by upgrading of the liquid hydrocarbon phase; or -transporting the oleic phase followed by upgrading of the oleic phase, said upgrading comprising decompression of the oleic phase, separation of the oleic phase into the gaseous hydrocarbon phase and into the liquid hydrocarbon phase and recycling of the gaseous hydrocarbon phase in order to provide at least partly the liquid solvent.

The invention moreover relates to an installation for treating hydrocarbons comprising: -a line for supplying a stream of hydrocarbons; -a line for supplying liquid solvent opening out into the line for supplying a stream of hydrocarbons; -a unit for separating water/hydrocarbons by gravity, fed by the line for supplying a stream of hydrocarbons; -a line for drawing off an oleic phase and a line for drawing off an aqueous phase, connected at the outlet of the water/hydrocarbons gravitational separation unit; -decompression means on the line for drawing off an oleic phase; -a liquid/gas separation unit fed by the line for drawing off an oleic phase; -a line for drawing off a gaseous hydrocarbon phase and a line for drawing off a liquid hydrocarbon phase connected at the outlet of the liquid/gas separation unit; -the line for drawing off a gaseous hydrocarbon phase feeding a line for recycling liquid solvent, said line for recycling liquid solvent feeding at least partly the line for supplying liquid solvent.

According to an embodiment, the aforementioned installation comprises compression means on the line for drawing off a gaseous hydrocarbon phase, and in which the liquid solvent supply line is fed by the line for recycling liquid solvent and by a line providing a supplement of liquid solvent.

According to an embodiment, the aforementioned installation comprises: -means for extracting hydrocarbons in an underground formation, from which stems the line for supplying a stream of hydrocarbons; -optionally means for removing solid materials mixed with the hydrocarbons; and -optionally means for degassing the hydrocarbons, on the line for supplying a stream of hydrocarbons.

According to an embodiment, the aforementioned installation comprises: -a unit for producing hydrocarbons; -an intermediate unit, comprising the unit for separating water/hydrocarbons by gravity; -a unit for upgrading hydrocarbons; -a first conduit for transporting hydrocarbons from the hydrocarbon production unit and feeding the intermediate unit; and -a second conduit for transporting hydrocarbons from the intermediate unit and feeding the unit for upgrading hydrocarbons.

According to an embodiment, the intermediate unit comprises the liquid/gas separation unit, the installation also optionally comprising a line for supplying additive opening out into the second conduit for transporting hydrocarbons, and: -the line for recycling liquid solvent is comprised in the intermediate unit; or -the line for recycling liquid solvent stems from the intermediate unit and opens out into the first conduit for transporting hydrocarbons.

According to an embodiment, the upgrading unit comprises the liquid/gas separation unit, and: -the line for recycling liquid solvent stems from the upgrading unit and feeds the intermediate unit; or -the line for recycling liquid solvent stems from the upgrading unit and opens out into the first conduit for transporting hydrocarbons.

According to an embodiment, the aforementioned method is applied in an installation as described above.

With the present invention it is possible to overcome the drawbacks of the state of the art. More particularly it provides a method for treating hydrocarbons giving the possibility of carrying out an oil/water separation more efficiently, more simply, more economically and more rapidly than in the existent methods, in particular for heavy oils.

This is accomplished by means of the use of a light solvent based on C3-C6 alkanes (preferably based on C3 and C4 alkanes), which is mixed with hydrocarbons so as to significantly increase the AN degree of the latter. In this way, oil/water separation is facilitated. The light solvent may then be easily recovered (separated from the hydrocarbons with which it was mixed) without resorting to distillation, and thereby be recycled.

According to certain particular embodiments, the invention also has one or preferably several of the advantageous features listed below.

-The size of the water/oil separators may be reduced, as compared with the state of the art in which naphtha is mixed to production crude before water/oil separation.

-The heating needs are reduced at the stage of the water/oil separation, as compared with the state of the art in which the naphtha is mixed with the production crude before water/oil separation.

-The API degree of the hydrocarbons is more significantly increased than in the state of the art in which naphtha is mixed with the production crude before water/oil separation, which increases the water/oil separation rate. Typically, the dwelling time in the separators may thus be reduced to a few minutes instead of one or several hours.

-The recovery of the solvent may be carried out in a simple way, at a pressure close to atmospheric pressure, and without using any distillation column. The solvent is recycled with a minimum of losses (the losses are in particular reduced as compared with the conventional scheme).

-According to the embodiments, the solvent may also be used for fluidifiying hydrocarbons and facilitating their transport, between the production site and the water/oil separation unit and/or between the water/oil separation unit and the upgrading unit.

-As compared with document WO 99/19425, the invention provides a much simpler method and installation for treating hydrocarbons, the water being in particular removed by simple separation by gravity and without resorting to partial vaporization.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 schematically illustrates an embodiment of the installation for treating hydrocarbons according to the invention.

Figs. 2 to S schematically illustrate four alternative embodiments of the installation for treating hydrocarbons according to the invention.

DESCRTPTTON OF EMBODTMENTS OF THE INVENTTON

The invention is now described in more detail and in a non-limiting way in

the following description.

Treatment of hydrocarbons containing water In the following, the terms of << upstream>> and <<downstream>> are defined relatively to the direction of transport of the different fluids in the installation.

With reference to Fig. 1, an installation for treating hydrocarbons according to the invention comprises a line for supplying a stream of hydrocarbons 1. The stream of hydrocarbons to be treated arrives through this hydrocarbon stream supply line 1. It may comprise a liquid phase and a gas phase and it contains water.

Degassing means 2 for the hydrocarbons may be provided on the hydrocarbon stream supply line 1. A line for drawing off gases 3 is then connected at the outlet of the degassing means 2. Thus, a majority of the gas phase of the hydrocarbon stream may be removed at this stage, if necessary.

The degassing means 2 may comprise one (or play the role of one) "slug catcher", i.e. provide a function for preventing obturations or overpressures from passing to the subsequent levels of the method.

Optionally, pumping means 4 may be provided on the hydrocarbon stream supply line 1, downstream from the degassing means 2, in order to compress the stream of hydrocarbons if necessary.

The installation according to the invention also comprises a line for supplying liquid solvent 5, which opens out into the hydrocarbon stream supply line 1. Thus, the stream of hydrocarbons and the liquid solvent are mixed, in order to provide an intermediate stream of hydrocarbons. Provision may be made for a static or motor-driven mixer in order to ensure mixing of the fluids stemmed from both of these lines, but this is generally not required.

The liquid solvent is itself based on hydrocarbons and comprises a mass proportion of C-C6 alkanes greater than or equal to 80%, preferably greater than or equal to 85%, most particularly greater than or equal to 90% and ideally greater than or equal to 95%.

According to an embodiment, the liquid solvent comprises a mass proportion of C3-C4 alkanes greater than or equal to 80%, preferably greater than or equal to 85%, most preferably greater than or equal to 90% and ideally greater than or equal to 95%. This liquid solvent is therefore generally of the LPG type (Liquefied Petroleum Gas).

According to another embodiment, the liquid solvent comprises a mass proportion of C5 and C6 alkanes greater than or equal to 80%, preferably greater than or equal to 85%, most preferably greater than or equal to 90% and ideally greater than or equal to 95%.

The initial stream of hydrocarbons is generally a so-called heavy or extra heavy oil. Preferably, this initial stream of hydrocarbons has an API degree comprised between 5 and 25.

The API degree may be measured according to the ASTM D287 Standard.

By adding a liquid solvent it is possible to considerably increase the API degree; thus the intermediate stream of hydrocarbons preferably has an API degree greater than or equal to 30, most preferably greater than or equal to 35, ideally greater than or equal to 40.

The selection of the solvent essentially based on C3-C6 alkanes is optimum.

Indeed, hydrocarbons having more than 6 carbon atoms are difficult to recycle once they are mixed with the initial stream of hydrocarbons and they do not allow any increase in the API degree in a completely satisfactory way.

Tn this respect, the selection of a solvent essentially based on C3-C4 alkanes generally provides particularly good results.

On the other hand, C1 and C2 alkanes are very lightweight, and it would be necessary to work at very cold temperatures or at very high pressures in order to be able to have them available in liquid form, which is indispensable for being able to mix them with the initial stream of hydrocarbons in order to increase the API degree.

The molar ratio of the hydrocarbon proportions of the initial stream of hydrocarbons and of hydrocarbons of the liquid solvent is selected so as to obtain the desired API degree in the intermediate stream of hydrocarbons. This molar ratio is also adjusted according to the risk of precipitation by deposits of asphaltenes.

Generally, this molar ratio is comprised between 0.2 and 5, preferably between 0.5 and 2 notably between 0.8 and 1.25, and ideally is close to 1. This corresponds to a mass proportion of solvent much less than what is used in the state of the art with solvents of the naphtha type.

The exact composition of the liquid solvent, and for example the relative C3 and C4 proportions (in the case of a liquid solvent essentially based on C3 and C4 alkanes) may be selected according to the constraints of the method or, preferably may be itself considered as a constraint (for example because a determined LPG stream is available within the scope of the overall hydrocarbon producing and treating method). In the second case, other parameters of the method are adjusted depending on this constraint (ratio of the hydrocarbon molar proportions of the initial stream of hydrocarbons and of hydrocarbons of the liquid solvent, operating temperature and pressure...).

The intermediate stream of hydrocarbons, via the hydrocarbon stream supply line 1, enters a water/hydrocarbons gravitational separation unit 6. By <<water/hydrocarbons gravitational separation unit>> is designated any set of means which may separate a mixture of water and of liquid hydrocarbons into an aqueous phase and an oleic phase by the action of gravity, the aqueous phase being denser than the oleic phase.

Therefore, the water/hydrocarbons gravitational separation unit 6 is not a unit which may carry out a water/hydrocarbon separation by vaporization (flash decompression). This is advantageous since sudden changes in pressure are counter-productive for water/hydrocarbons separation; indeed they induce strong shearing which tends to regenerate emulsions. Within the scope of the method according to the invention, one therefore operates at constant or quasi constant pressure during the water/hydrocarbons separation.

The water/hydrocarbons gravitational separation unit 6 may comprise any separator known to one skilled in the art, with or without means for destabilizing emulsions, such as means for spraying the oil/water interface, and with or without heating means.

The water/hydrocarbons gravitational separation unit 6 may for example be an apparatus as described in document WO 2005/100512.

If necessary, the water/hydrocarbons gravitational separation unit 6 may comprise desalting means. The desalting means typically comprise at least two successive separators, with a demineralized water supply line between the separators.

Separation by gravity carried out within the water/hydrocarbons gravitational separation unit 6 is generally accomplished at a pressure comprised between 3 and 15 bars, preferably between 5 and 10 bars, for example between 7 and 8 bars (all the pressure values mentioned in the present application are absolute values).

Generally, it is unnecessary to heat the initial stream of hydrocarbons or the intermediate stream of hydrocarbons or further to provide heating during separation by gravity, since, the mixture of the initial stream of hydrocarbons with the liquid solvent allows a sufficient increase in the API degree of the hydrocarbons so that separation by gravity is carried out rapidly and efficiently without any heating (this is then performed at room temperature).

Separation by gravity provides an oleic phase and an aqueous phase, which are respectively drawn off in a line for drawing off an oleic phase 8 and a line for drawing off an aqueous phase 7.

The aqueous phase generally undergoes a subsequent treatment before, for example, being released into the environment or reused within the scope of the overall method for producing hydrocarbons. However, the quality of the water is better than in the methods of the state of the art; the aqueous phase contains a lesser proportion of hydrocarbons and a lesser proportion of solid particles (since the solid particles decant and are therefore more easily removed during the hydrocarbonlwater separation, because of the relatively large fluidity of the hydrocarbons). Therefore, the subsequent treatment of the aqueous phase may be more reduced and simpler than in the state of the art.

The oleic phase then undergoes a step for separation into a gaseous hydrocarbon phase and a liquid hydrocarbon phase, within a liquid/gas separation unit 12, fed by the line for drawing off an oleic phase 8. The gaseous hydrocarbon phase is sampled through a line for drawing off a gaseous hydrocarbon phase 14 and the liquid hydrocarbon phase is sampled through a line for drawing off a liquid hydrocarbon phase 13.

The oleic phase essentially has a same chemical composition as the intermediate stream of hydrocarbons (mixture of the initial stream of hydrocarbons and of the liquid solvent), except for the water content. The gaseous hydrocarbon phase from the separation in the liquid/gas separation unit 12 essentially has the same chemical composition as the liquid solvent. And the liquid hydrocarbon phase, from the liquid/gas separation unit 12, essentially has the same chemical composition as the initial stream of hydrocarbons (except for the water content).

In other words, the separation of the oleic phase into the gaseous hydrocarbon phase and the liquid hydrocarbon phase essentially amounts to again separating the intermediate stream of hydrocarbons (with a high API degree) into on one hand the initial stream of hydrocarbons (with a small API degree) cleared of the majority of its water and into on the other hand, the composition of hydrocarbons comprising in majority C-C6 alkanes (notably C3 and C4 alkanes according to an embodiment) which makes up the liquid solvent, in order to ensure recycling of this composition.

Preferably, with this separation step it is possible to recover in the form of the gaseous hydrocarbon phase, more than 50%, preferably more than 75%, most preferably more than 85%, ideally more than 90% or even more than 95%, in a molar proportion, of the hydrocarbons brought by the liquid solvent. However, it is not indispensable to recover the totality of these compounds, notably when the liquid hydrocarbon phase undergoes subsequent upgrading and/or refining steps during which the remaining fraction of the added compounds may be isolated.

Before proceeding with the step for separation into the gaseous hydrocarbon phase and the liquid hydrocarbon phase, the oleic phase stemming from the water/hydrocarbons gravitational separation is decompressed by decompression means 9 provided on the line for drawing off an oleic phase 8.

Typically, the pressure of the oleic phase is reduced to between 1 and 3 bars, preferably between 1 and 2 bars for the needs of the separation of the oleic phase into the gaseous hydrocarbon phase and the liquid hydrocarbon phase. The separation is carried out all the better since the pressure is low, however, it is generally not recommended to carry out the separation exactly at atmospheric pressure (1 bar), since this complicates subsequent recompression of the gaseous hydrocarbon phase.

The oleic phase may also be heated if necessary, prior to the separation or during the separation, by heating means 10, 11. For example, it is possible to provide a main heating by external heating means 11, preceded by preliminary heating with a heat exchanger 10, against the cooling of the liquid hydrocarbon phase stemming from the separation step.

However, the heating needs at this stage generally are actually less substantial than in the state of the art, for distilling the heavy oil/naphtha mixture. These heating needs may even be inexistent.

Generally, temperature and pressure conditions are selected (as well as the molar ratio of the hydrocarbon proportions of the initial stream of hydrocarbons and of hydrocarbons of the liquid solvent) so that: -the solvent added to the initial stream of hydrocarbons is in the liquid state, and remains in the liquid state during the water/hydrocarbons gravitational separation; and -this solvent is in the gas state during the separation of the oleic phase.

This choice of conditions is simply carried out by studying the phase diagram of the solvent.

The gaseous hydrocarbon phase is recycled in order to provide at least partly the aforementioned liquid solvent, which assumes compression and liquefaction of this phase.

For this purpose, the line for drawing off a gaseous hydrocarbon phase 14 feeds a line for recycling liquid solvent 23, said liquid solvent recycling line 23 in turn feeding at least partly the liquid solvent supply line 5. Compression means 16, 18 are provided on the line for drawing off a gaseous hydrocarbon phase 14, with cooling means 17, 19 at the outlet of each compressor or compressor stage. One or several compression stages are to be considered but preferentially a single compression stage. A separation element 15 may also be provided on the line for drawing off a gaseous hydrocarbon phase 14. This separation element 15, upstream from the compression means 16, 18, protects the latter, since these compression means 16, 18 should only compress gases.

Pumping means 22 are also provided on the line for recycling liquid solvent 23. A separation element 20 may be provided upstream from the pumping means 22, in order to protect the latter since the pumping means 22 should only compress liquids.

Generally, supplemental provision of liquid solvent may be carried out. Thus, the liquid solvent supply line 5 may be fed both by the liquid solvent recycling line 23 and by a line for providing supplemental liquid solvent 24.

Integration of the invention within the scope of production of hydrocarbons The invention may be applied within the scope of the production of hydrocarbons, notably of petroleum. In this case, the installation according to the invention comprises means for extracting hydrocarbons in an underground formation, and the provision of the initial stream of hydrocarbons comprises the extraction of hydrocarbons from the underground formation.

Preferably, the initial stream of hydrocarbons is thus a stream of crude oil.

Preferably, no product or compound is added to the hydrocarbons between the extraction from the underground formation and the steps for adding liquid solvent.

The means for extracting hydrocarbons may for example comprise a set of wells (or cluster >>).

The initial stream of hydrocarbons, which is brought to the water/hydrocarbons gravitational separation unit 6 via the line for supplying a stream of hydrocarbons 1, preferably contains less than 20,000 ppm of solid materials (by mass), most preferably less than 10,000 ppm of solid materials, and ideally less than 5,000 ppm of solid materials.

The water/hydrocarbons gravitational separation unit 6 may conventionally comprise means for removing solid materials, in order to further reduce the solid material content subsequently in the method.

With reference to Figs. 2-5, within the scope of production of hydrocarbons, the installation according to the invention generally comprises: -a unit for producing hydrocarbons 101; -an intermediate unit 103; and -a unit for upgrading hydrocarbons 105.

The unit for producing hydrocarbons 101 notably comprises the aforementioned means for extracting hydrocarbons. It may be on land or offshore.

The intermediate unit 103 comprises a set of treatment means and in particular the water/hydrocarbons gravitational separation unit 6. It may be on land or offshore (underwater or at the surface). The hydrocarbon upgrading unit 105 (located on land) is adapted so as to upgrade the hydrocarbons (i.e. achieve their upgrading). This hydrocarbon upgrading unit 105 comprises a set of means for converting the hydrocarbons into lighter compounds. It may comprise refining means or else conversion means prior to refining.

Between the unit for producing hydrocarbons 101 and the intermediate unit 103, the hydrocarbons are conveyed through a first hydrocarbon transport conduit 102. Between the intermediate unit 103 and the hydrocarbon upgrading unit 105, the hydrocarbons are conveyed through a second hydrocarbon transport conduit 104.

The distance between the hydrocarbon production unit 101 (or certain sites of the hydrocarbon production unit 101, when the latter is geographically extensive) and the intermediate unit 103 may be greater than 1 km, or even greater than 10 km and even greater than 100 km. Also, the distance between the intermediate unit 103 and the hydrocarbon upgrading unit 105 may be greater than 1 km, or even greater than 10 km and even greater than 100 km.

According to a first embodiment, illustrated in Fig. 2, the set of means described above allowing separation of the oil and of the water as well as supply, circulation and recycling of the liquid solvent, are comprised in the intermediate unit 103. Tn particular, the intermediate unit 103 comprises the liquid/gas separation unit 12 and the line for recycling liquid solvent 106.

Therefore, it is within the intermediate unit 103 that the initial stream of hydrocarbons is mixed with the liquid solvent, the intermediate stream of hydrocarbons is separated into an oleic phase and an aqueous phase, that the oleic phase is decompressed and separated into a gaseous hydrocarbon phase and a liquid hydrocarbon phase, and that the gaseous hydrocarbon phase is recycled in order to partly provide the liquid solvent.

According to a second embodiment, illustrated in Fig. 3, the set of means described above allowing separation of the oil and of the water as well as supply, circulation and recycling of the liquid solvent, are distributed between the intermediate unit 103 and the hydrocarbon upgrading unit 105. More specifically, the separation by gravity is carried out in the intermediate unit 103, but the recovery of the compounds forming the liquid solvent is only carried out in the hydrocarbon upgrading unit 105, which comprises the liquid/gas separation unit 12. The liquid solvent recycling line 106 then leaves the upgrading unit 105 and feeds the intermediate unit 103.

Therefore it is within the intermediate unit 103 that the initial stream of hydrocarbons is mixed with the liquid solvent, that the intermediate stream of hydrocarbons is separated into an oleic phase and an aqueous phase. Next, it is within the hydrocarbon upgrading unit 105 that the oleic phase is decompressed and separated into a gaseous hydrocarbon phase and a liquid hydrocarbon phase, and that the gaseous hydrocarbon phase is recycled in order to partly provide the liquid solvent. The liquid solvent is then returned towards the intermediate unit 103. Tn this embodiment, the second hydrocarbon transport conduit 104 coincides with the line for drawing off an oleic phase 8.

According to a third embodiment, illustrated in Fig. 4, the set of means described above allowing separation of the oil and of the water as well as supply, circulation and recycling of the liquid solvent, are distributed between the intermediate unit 103 and the hydrocarbon production unit 101. More specifically, separation by gravity is carried out in the intermediate unit 103, as well as the recovery of the compounds forming the liquid solvent (the intermediate unit 103 comprising the liquid/gas separation unit 12). The liquid solvent recycling line 106 then leaves the intermediate unit 103 and opens out into the hydrocarbon production unit 101 (preferably at the head of the well) or into the first hydrocarbon transport conduit 102 (preferably towards the beginning of this conduit, i.e. at the outlet of the hydrocarbon production unit 101).

Therefore it is preferably at the hydrocarbon production unit 101 that the initial stream of hydrocarbons is mixed with the liquid solvent. Next, it is within the intermediate unit 103 that the intermediate stream of hydrocarbons is separated into an oleic phase and an aqueous phase, that the oleic phase is decompressed and separated into a gaseous hydrocarbon phase and a liquid hydrocarbon phase, and that the gaseous hydrocarbon phase is recycled in order to partly provide the liquid solvent. The liquid solvent is then returned towards the hydrocarbon production unit 101. In this embodiment, the first hydrocarbon transport conduit 102 essentially conveys the intermediate stream of hydrocarbons described above.

According to a fourth embodiment, illustrated in Fig. 5, the set of means described above allowing separation of the oil and of the water as well as circulation and recycling of the liquid solvent, are distributed between the hydrocarbon production unit 101, the intermediate unit 103 and the upgrading unit 105. More specifically, the liquid solvent is mixed with the initial stream of hydrocarbons at the outlet of the hydrocarbon production unit 101, separation by gravity is carried out in the intermediate unit 103 and recovery of the compounds forming the liquid solvent is carried out in the upgrading unit 105 (which comprises the liquid/gas separation unit 12). The liquid solvent recycling line 106 then leaves the upgrading unit 105 and opens out into the hydrocarbon production unit 101 (preferably at the head of the well), or into the first hydrocarbon transport conduit 102 (preferably towards the beginning of this conduit, i.e. at the outlet of the hydrocarbon production unit 101).

Therefore, it is preferably at the hydrocarbon production unit 101 that the initial stream of hydrocarbons is mixed with the liquid solvent. Next, it is within the intermediate unit 103 that the intermediate stream of hydrocarbons is separated into an oleic phase and an aqueous phase. Finally, it is within the upgrading unit 105 that the oleic phase is decompressed and separated into a gaseous hydrocarbon phase and a liquid hydrocarbon phase, and that the gaseous hydrocarbon phase is recycled in order to partly provide the liquid solvent. The liquid solvent is then returned towards the hydrocarbon production unit 101. In this embodiment, the first hydrocarbon transport conduit 102 essentially conveys the intermediate stream of hydrocarbons described above. Still in this embodiment, the second hydrocarbon transport conduit 104 coincides with the line for drawing off an oleic phase 8.

The embodiments of Figs. 3 and S have the advantage of facilitating transport of the hydrocarbons in the second hydrocarbon transport conduit 104 up to the upgrading unit 105, since the stream of hydrocarbons is mixed at this stage with the liquid solvent, which significantly reduces its viscosity.

Conversely, in the embodiments of Figs. 2 and 4, it is generally necessary to provide means for fluidifying the hydrocarbons circulating in the second hydrocarbon transport conduit 104. These may be heating means and/or an additive supply line 107 opening out into the second hydrocarbon transport conduit 104 and allowing injection into the hydrocarbons of an additive for reducing viscosity (or DRA) of the surfactant type combined with a composition of hydrocarbons with a low or moderate API degree, or even only with a composition of hydrocarbons with a low or moderate API degree, such as naphtha for example.

The embodiments of Figs. 4 and 5 have the advantage of facilitating the transport of the hydrocarbons in the first hydrocarbon transport conduit 102 as far as the intermediate unit 103, since the stream of hydrocarbons is mixed at this stage with the liquid solvent, which significantly reduces its viscosity.

Conversely, in the embodiments of Figs. 2 and 3, it may be necessary to provide means for fluidifying the hydrocarbons circulating in the first hydrocarbon transport conduit 102, of the same type as above. However, such means for fluidifying the hydrocarbons may be unnecessary when the extracted hydrocarbons are sufficiently hot (this for example may be the case within the scope of an extraction with the SAGD process) and/or when the first hydrocarbon transport conduit is relatively short, the intermediate unit 103 being positioned in proximity to the hydrocarbon production unit 101.

Claims

CLAIMS1. A method for treating hydrocarbons, said method comprising: -providing an initial stream of hydrocarbons comprising water, comprising the extraction of hydrocarbons from an underground formation; -adding a liquid solvent into the initial stream of hydrocarbons in order to provide an intermediate stream of hydrocarbons, said liquid solvent comprising a mass proportion of C3-C6 alkanes greater than or equal to 80%; -gravitationally separating the intermediate stream of hydrocarbons into an oleic phase and an aqueous phase; -decompression of the oleic phase and separation of the oleic phase into a gaseous hydrocarbon phase and a liquid hydrocarbon phase; -recycling the gaseous hydrocarbon phase in order to provide at least partly the liquid solvent; and -recovering the liquid hydrocarbon phase.
2. The method according to claim 1, wherein the initial stream of hydrocarbons has an API degree comprised between 5 and 25 and the intermediate stream of hydrocarbons has an API degree greater than or equal to 30, preferably greater than or equal to 35, most preferably greater than or equal to 40.
3. The method according to claim 1 or 2, wherein the liquid solvent comprises a mass proportion of C3 and C4 alkanes greater than or equal to 80% preferably greater than or equal to 85%, most preferably greater than or equal to 90%, ideally greater than or equal to 95%.
4. The method according to one of claims 1 to 3, wherein the recycling of the gaseous hydrocarbon phase in order to provide at least partly the liquid solvent comprises compression of the gaseous hydrocarbon phase and optionally a supplement of liquid solvent.
5. The method according to one of claims 1 to 4, wherein the steps for providing the initial stream of hydrocarbons comprises: -degassing of the extracted hydrocarbons; and/or -removing solid materials mixed with the extracted hydrocarbons.
6. The method according to one of claims 1 to 5, wherein the initial stream of hydrocarbons comprises less than 20,000 ppm of solid materials, preferably less than 10,000 ppm of solid materials, most preferably less than 5,000 ppm of solid materials, in a mass proportion.
7. The method according to one of claims 1 to 6, wherein: -separation by gravity of the intermediate stream of hydrocarbons is carried out at a pressure comprised between 3 and 15 bars, preferably between 5 and 10 bars; and/or -separation of the oleic phase into the gaseous hydrocarbon phase and into the liquid hydrocarbon phase is carried out at a pressure comprised between 1 and 3 bars, preferably between 1 and 2 bars.
8. The method according to one of claims ito 7 further comprising: -conveying the liquid hydrocarbon phase followed by upgrading of the liquid hydrocarbon phase; or -conveying the oleic phase followed by upgrading of the oleic phase, said upgrading comprising decompression of the oleic phase, separation of the oleic phase into a gaseous hydrocarbon phase and into the liquid hydrocarbon phase and recycling of the gaseous hydrocarbon phase in order to provide at least partly the liquid solvent.
9. The method according to one of claims 1 to 8, wherein more than 75%, preferably more than 85%, or more than 90%, or more than 95% in a molar proportion, of the hydrocarbons provided by the liquid solvent are recovered in the gaseous hydrocarbon phase.
10. An installation for treating hydrocarbons comprising: -a line for supplying a stream of hydrocarbons (1); -means for extracting hydrocarbons in an underground formation, from which stems the line for supplying a stream of hydrocarbons (1); -a line for supplying liquid solvent (5) opening out into the line for supplying a stream of hydrocarbons (1); -a water/hydrocarbons gravitational separation unit (6) fed by the hydrocarbon stream supply line (1); -a line for drawing off an oleic phase (8) and a line for drawing off an aqueous phase (7), connected at the outlet of the water/hydrocarbons gravitational separation unit (6); -decompression means (9) on the line for drawing off an oleic phase (8); -a liquid/gas separation unit (12), fed by the line for drawing off an oleic phase (8); -a line for drawing off a gaseous hydrocarbon phase (14) and a line for drawing off a liquid hydrocarbon phase (13) connected at the outlet of the liquid/gas separation unit (12); -the line for drawing off a gaseous hydrocarbon phase (14) feeding a liquid solvent recycling line (23), said liquid solvent recycling line (23) feeding at least partially the liquid solvent supply line (5).
11. The installation according to claim 10 comprising compression means (16, 18) on the line for drawing off a gaseous hydrocarbon phase (14) and in which the liquid solvent supply line (5) is fed by the liquid solvent recycling line (23) and by a line for supplying supplemental liquid solvent (24).
12. The installation according to claim 10 or 11, comprising: -means for removing solid materials mixed with the hydrocarbons; and/or -means (2) for degassing the hydrocarbons, on the hydrocarbon stream supply line (1).
13. The installation according to one of claims 10 to 12, comprising: -a unit for producing hydrocarbons (101); -an intermediate unit (103), comprising the water/hydrocarbons gravitational separation unit (6); -a unit for upgrading hydrocarbons (105); -a first hydrocarbon transport conduit (102) stemming from the hydrocarbon production unit (101) and feeding the intermediate unit (103); -a second hydrocarbon transport conduit (104) stemming from the intermediate unit (103) and feeding the unit for upgrading hydrocarbons (105).
14. The installation according to claim 13, wherein the intermediate unit (103) comprises the liquid/gas separation unit (12), the installation optionally also comprising an additive supply line (107) opening out into the second hydrocarbon transport conduit (104), and wherein: -the liquid solvent recycling line (106) is comprised in the intermediate unit (103); or -the liquid solvent recycling line (106) stems from the intermediate unit (103) and opens out into the first hydrocarbon transport conduit (102).
15. The installation according to claim 13, wherein the upgrading unit (105) comprises the liquid/gas separation unit (12), and wherein: -the liquid solvent recycling line (106) stems from the upgrading unit (105) and feeds the intermediate unit (103); or -the liquid solvent recycling line (106) stems from the upgrading unit (105) and opens out into the first hydrocarbon transport conduit (102).
16. The method according to one of claims 1 to 9, applied in an installation according to one of claims 10 to 15.