WO2011083421A1

WO2011083421A1 - Method for treating water and producing steam and steam-production facility

Info

Publication number: WO2011083421A1
Application number: PCT/IB2011/050022
Authority: WO
Inventors: Hung-Minh Dang; Bernard Gauthier; Pierre Pedenaud
Original assignee: Total S.A.
Priority date: 2010-01-06
Filing date: 2011-01-04
Publication date: 2011-07-14
Also published as: CA2785216A1; FR2954950A1; FR2954950B1

Abstract

The invention relates to a method for treating water and producing steam, which includes: providing feed water containing carbonate and/or bicarbonate ions, treating the feed water, feeding a boiler (8) with the treated feed water and generating steam in the boiler, in which the treatment of the feed water includes placing the feed water in contact with a gaseous composition including carbon dioxide. The invention also relates to a facility suitable for implementing said method, as well as to a method for extracting hydrocarbons implementing the above method.

Description

METHOD FOR WATER TREATMENT AND STEAM PRODUCTION AND STEAM PRODUCTION PLANT

FIELD OF THE INVENTION

The present invention relates to a water treatment process for the production of steam, as well as its application in the context of enhanced oil recovery. The invention also relates to a water treatment plant for the production of steam adapted to the implementation of the method above.

TECHNICAL BACKGROUND

The exploitation of global reserves of heavy stationary oils or high-viscosity mobile oils whose situation in the underground formations is too deep for open-pit extraction requires the use of thermal processes. These provide heat to the tank to heat the hydrocarbons, reduce their viscosity and make them more mobile for their production. The main thermal processes are:

- Gravity drainage assisted by steam;

- drainage by steam; and

cyclic stimulation by steam.

Steam Assisted Gravity Drainage (SAGD) is a thermal recovery technique in which horizontal pairs of injectors and generators are drilled into the formation with a typical spacing of about 5 m. The steam is injected to heat the hydrocarbons and mobilize them, so that they flow to the producing wells under the effect of gravity, assisted by a steam zone of increasing size. It is the most widely used thermal recovery technique for extra-heavy oils found in oil sands tanks.

Steam drainage is another method by which steam is continuously injected into dedicated wells (vertical, inclined, or horizontally) located around or adjacent to producing wells in a predetermined arrangement.

Cyclic Steam Stimulation is a single-well process in which steam is injected for a period of time and then allowed to permeate the subsurface formation and heat the hydrocarbons. Finally, the heated hydrocarbons and the condensation water are produced by the same well for a certain duration.

For all these processes, water is used to generate the steam, and the water consumption associated with the steam generation typically represents about three water bodies per mass of hydrocarbons produced. Thermal production may involve the consumption of clean water, but significant efforts are made to maximize the recycling of water from producing wells. In general, 85 to 95% of the water produced from production wells is recycled.

Steam generating devices can take many forms, which typically include one-pass boiler and conventional balloon boilers. It is necessary to have water of acceptable quality to supply the boilers and the steam generators.

One of the problems with steam generation is the presence of mineral contaminants in the water, mainly carbonates, sulphates and silica. When water is heated and converted to steam in a boiler, some mineral contaminants such as silica or sulphates tend to remain in the boiler. The boiler functions as a distillation unit, producing pure vaporized water while the concentrated mineral contaminants remain in the boiler and tend to form incrustations. These incrustations act as an insulator and reduce the efficiency of the boiler. They can thus lead to a failure of the boiler by overheating. In addition, the carbonates and bicarbonates can promote the phenomenon of priming water, that is to say the driving drops of boiler water in the steam. These can pollute the steam and make it eroding with respect to the walls it can meet. Carbonates and bicarbonates can also decompose to carbon dioxide as a result of the high temperature in the boiler, thus giving rise to acid corrosion phenomena.

Typical methods of removing mineral contaminants from the boiler feed water include precipitation ion exchange, reverse osmosis, electrodialysis, distillation and freezing.

With particular reference to the removal of carbonates and bicarbonates, the acidification of water by hydrochloric acid injection is generally used to convert carbonates and bicarbonates to carbon dioxide and / or lime injection (" softening lime ") for precipitating carbonates and bicarbonates in the form of calcium carbonate.

However, these methods involve the use of large quantities of chemicals.

There is therefore a real need to improve the treatment of water for the production of steam and in particular the treatment of carbonates and bicarbonates, reducing the consumption of chemicals. SUMMARY OF THE INVENTION

The invention relates primarily to a method of water treatment and steam production comprising:

supply of a feed water containing carbonate and / or bicarbonate ions;

- the treatment of the feed water;

feeding a boiler with the treated feed water;

- steam generation in the boiler;

wherein the treatment of the feedwater comprises contacting the feedwater with a gaseous composition comprising carbon dioxide.

In one embodiment, the boiler produces a flue gas that provides the gaseous composition comprising carbon dioxide.

According to one embodiment, the boiler operates in oxyfuel combustion.

According to one embodiment, the contacting of the feed water with the gaseous composition is carried out at a temperature greater than or equal to 60 ° C, preferably greater than or equal to 70 ° C, more particularly preferably higher or equal to 80 ° C, and ideally between 85 ° C and 95 ° C.

According to one embodiment, the gaseous composition comprises at least 5% by volume of carbon dioxide, preferably at least 10% by volume of carbon dioxide, more particularly preferably at least 20% by volume of carbon dioxide, and ideally at least 35% by volume of carbon dioxide.

According to one embodiment, the treatment of the feedwater also comprises:

- skimming of water; and or

- the deoiling of the water; and or

the treatment of mineral contaminants contained in the water by:

^■ ion precipitation in the water and removing the precipitated material, preferably comprising softening of water by injection of lime; and or

^■ reducing the mineral content of the water by ion exchange on an ion exchange resin; and or

^■ reverse osmosis water treatment; and or

^■ water treatment by evaporation; and or

^■ Injection crystallization agents and recovering crystallized species; and or

^■ Injection silica deposition inhibiting agents.

The invention also relates to a steam production plant comprising:

- a boiler ;

- a water supply system connected to the inlet of the boiler;

a steam withdrawal line connected at the outlet of the boiler;

the water supply system comprising a water decarbonation unit, which comprises means for contacting the water with a gaseous composition comprising carbon dioxide.

According to one embodiment, the installation comprises:

- A combustion gas withdrawal line connected to the output of the boiler and feeding the decarbonation unit.

According to one embodiment, the decarbonation unit comprises:

- a water storage container;

- Gaseous composition injection means comprising carbon dioxide in the water storage container;

means for recovering emitted gas.

According to one embodiment, said means for bringing water into contact with a gaseous composition comprising carbon dioxide comprise a packed or packed column and / or a cyclonic device and / or an ejector and / or venturi device.

According to one embodiment, the water supply system comprises:

- a skimming unit; and or

- a deoiling unit; and or

means for treating mineral contaminants, comprising:

^■ ion precipitation means in the water and removing the precipitated material, preferably comprising means for softening of water by injection of lime; and or

an ion exchange resin; and or

^■ a reverse osmosis unit; and or

■ an evaporation unit; and or

^■ means for injecting agents crystallization and recovery of crystalline species and / or

^■ the injection means of silica scale inhibitors.

In one embodiment, the vapor withdrawal line is connected to an inlet of an injection well disposed in a subterranean formation containing hydrocarbons.

According to one embodiment, the water supply system is fed at least partially by a water recycling pipe, connected at the outlet of a water recovery system of a hydrocarbon production facility.

According to one embodiment, the installation comprises a purge line connected at the outlet of the boiler, said purge duct optionally supplying the water supply system.

The subject of the invention is also a process for extracting hydrocarbons in an underground formation, comprising:

the production of steam according to the process described above;

- The injection of steam produced in at least one injection well disposed in the subterranean formation;

the recovery of hydrocarbons and production water in at least one extraction well disposed in the underground formation; de-oiling of the production water and the use of de-oiled production water as feed water in the steam production process.

The present invention overcomes the disadvantages of the state of the art. More particularly, it provides an improved process for treating water intended for the production of steam, and in particular for treating carbonates and bicarbonates, which results in reduced consumption of chemicals.

This is accomplished by contacting the boiler feed water with a gaseous flow comprising carbon dioxide, which results in acid decarbonation of the water without necessarily using hydrochloric acid. The gaseous flow comprising carbon dioxide can be obtained from gases emitted by the steam generation process itself, in particular from a combustion gas, and especially from the combustion gas from the boiler. .

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

The invention makes it possible to concentrate the carbon dioxide emitted throughout the steam generation process, including the treatment of the water, at the end of the water decarbonation step, and to avoid a contrario the emission of two separate streams of carbon dioxide (one at the boiler and the other at the decarbonation). The presence of the carbon dioxide emitted in the form of a single concentrated stream makes it possible to facilitate the subsequent treatment of this carbon dioxide by limiting the number of equipment required or their size, and by increasing the effectiveness of the treatment.

- The chlorinated, sulfur or fluorinated compounds present in the flue gas can be captured in the boiler feedwater instead of being discharged, which reduces the harmfulness of any releases into the atmosphere.

The invention can be implemented with a minimum modification of the existing installations.

The invention is particularly advantageous in the case where the feed water of the boiler contains a high content of carbonates and bicarbonates. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 schematically shows an embodiment of an installation according to the invention.

FIG. 2 is a diagram representing the evolution of the pH as a function of time (in minutes on the x-axis) of the production water during the decarbonation reaction carried out according to the invention, and for flow rates of gas of 10, 50 and 100 mL / min (see Example 2).

FIG. 3 is a diagram showing the concentration of bicarbonates (in mol / L) in the production water before the decarbonation reaction (checkerboard bars), at the end of the decarbonation reaction (white bars) and at Result of the decarbonation reaction after degassing the residual CO2 in water (black bars) for different experiments (see Example 2). DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is now described in more detail and without limitation in the description which follows.

Steam generation

According to the present invention, and with reference to FIG. 1, steam is produced in a boiler 8, an outlet of which is connected to a vapor withdrawal pipe 9. The boiler 8 may be a conventional balloon boiler or an "ounce through" steam generator (OTSG).

"Once-through" steam generators typically produce

80% of steam and 20% of purge water, while the so-called conventional boilers (drum boilers or pulverized coal boilers or entrained fluidized bed boilers) have a vaporization efficiency close to 100%.

Depending on the type of boiler, a flow of purge water can be recovered at the outlet of the boiler 8, in a purge line 14.

The boiler 8 is supplied with water which has been previously treated in order to reduce the amount of carbonate and bicarbonate ions present in the water. Thus, there is provided a water supply system 13 for supplying water to the boiler.

The feed and water treatment system 13 comprises at least one water supply pipe 1. The water flowing in the water feed pipe 1 contains CO 3 ² and / or bicarbonate carbonate ions. HCO3 ^". For example, the water flowing in the pipe water supply 1 may comprise between 50 and 10,000, preferably between 100 and 5000 mg / L of carbonate and bicarbonate ions. In general, this water also contains other mineral species, including silica, magnesium and calcium ions ...

In a schematic manner, the water supply system 13 comprises a decarbonation unit 6, and possibly other (complementary) means of water treatment. These other means of water treatment can include:

- A skimming unit 2 (which allows a first deoiling);

a deoiling unit 3 of flotation type;

means for treating inorganic contaminants 4, comprising, for example, precipitation means, ion exchange resins and / or evaporation means.

In general, and taking as reference the direction of flow of water, there is upstream downstream: first the skimming unit 2 (if present), then the de-oiling unit 3 ( if it is present) and finally the means for treating the mineral contaminants 4 and the decarbonation unit 6. Depending on the case, the means for treating the inorganic contaminants 4 may be arranged upstream of the decarbonation unit 6 (like this is shown in Figure 1), or downstream of the decarbonation unit 6, or even partially upstream and partially downstream of the decarbonation unit 6 when the mineral contaminants treatment means 4 comprises several parts.

So, in general, the water first undergoes a skimming step

(optional) in skimming unit 2, during which suspended materials (suspended solids and hydrocarbon drops) are removed from the water. A hydrocarbon recovery line 11 may thus be provided at the outlet of the skimming unit 2. Said hydrocarbon recovery line 11 is advantageously directed towards a system for treating and collecting hydrocarbons (not shown). .

Then, the water undergoes an (optional) de-oiling step in the de-oiling unit 3 (of the flotation type) in order to continue and refine the withdrawal of the suspended materials (mainly the drops of hydrocarbons and possibly solids in suspension). The deoiling unit 3 is preferably an induced gas flotation unit, in which a gas is degassed in water. The gas bubbles adhere to the suspended materials and bring them to the surface where they can be removed with the means skimming. An additional hydrocarbon recovery line 12 may thus be provided at the outlet of the deoiling unit 3. Said additional hydrocarbon recovery line 12 is advantageously directed towards a hydrocarbon treatment and collection system (not shown).

According to the invention, the treatment of water to remove dissolved mineral contaminants includes the decarbonation of water within the decarbonation unit 6.

This decarbonation is carried out by contacting the water with a gaseous composition comprising carbon dioxide. According to the preferred embodiment illustrated, this gaseous composition is derived from the combustion gas coming from the boiler 8. Preferably, all of the combustion gas coming from the boiler 8 is brought into contact with the water during the decarbonation .

The decarbonation of water is induced by the carbon dioxide contained in the gaseous composition: the carbon dioxide dissolves in water to form carbonic acid H2CO3; and bicarbonate ions HCO3 ^- react with carbonic acid to produce carbon dioxide according to the following reaction:

HCO3 ^" + H2CO3 H ₂ O + OH ^" + 2 CO ₂

In addition, the carbonate ions are converted to bicarbonate ions under acidic conditions. Thus, in the end, the presence of carbon dioxide makes it possible to reduce the content of carbonate and bicarbonate ions in water, and to enrich the gaseous composition with carbon dioxide.

It is estimated that for an example of an installation whose boiler produces

1350000 Nm ³ / h of fumes, it is possible to treat 270000 m ³ of water containing 2 g / L of HCO3 if the reaction has an efficiency of 100%. Since this theoretical quantity of water that can be treated is much greater than the real needs of the installation, the decarbonation according to the invention functions even if the reaction efficiency is much less than 100% (depending on the contact time water / gas).

The decarbonation unit 6 may take the form of any device for contacting a liquid with a gas flow. For example, it may take the form of a packed or packed column in which a downward flow of water intersects an upward flow of gaseous composition; or it may comprise a cyclonic device; or it may comprise an ejector or venturi device. But according to a preferred embodiment simpler to implement, the decarbonation unit 6 may simply comprise a water storage container (such as a storage tank) and gas composition injection means in the water storage container. In all cases, a gas recovery pipe 7 is provided.

Thus, according to the preferred embodiment, the invention requires few modifications compared to a conventional installation, since the conventional installation generally already comprises a water storage container upstream of the boiler 8. It is therefore sufficient to put implement the invention to provide gaseous composition injection means in the water storage container, preferably constituted by a gas diffuser (for example of the same type as used in the induced gas flotation unit) ) which is disposed towards the bottom of the storage container; providing a combustion gas withdrawal line 10 from the boiler 8 and supplying the aforementioned injection means; and finally to provide the water storage container of the above-mentioned emitted gas recovery line 7.

Preferably, the water storage container has a retention time greater than or equal to 30 minutes, or even greater than or equal to 1 hour, in order to allow the decarbonation to be carried out with sufficient effectiveness. In general, the water storage containers in existing installations have retention times of 5 to 8 hours, and they are therefore perfectly compatible with the invention.

So that the carbon dioxide injected and produced during the decarbonation does not remain dissolved in the water and is properly degassed before entering the boiler 8, it is important to work at high temperature. Thus, the decarbonation step is preferably carried out at a temperature greater than or equal to 60 ° C, in particular greater than or equal to 70 ° C, more preferably greater than or equal to 80 ° C, and ideally between 85 ° C and 95 ° C. According to a preferred embodiment, it is unnecessary to provide heating water at the decarbonation stage or before it, because the water used naturally has a high temperature. This is particularly the case when the water is at least partially recycled from steam previously generated.

If the water temperature is not high enough, it is possible to improve the degassing of carbon dioxide by providing a slight depression in the decarbonation unit 6.

When the boiler 8 is operating in normal combustion, the combustion gas typically comprises about 10% of carbon dioxide, 15% water by volume and about 75% nitrogen by volume and traces of oxygen. Nitrogen is an inert gas with respect to decarbonation.

It is possible to operate the boiler 8 with an excess of air. It is also possible to operate the boiler 8 in oxycombustion, that is to say using almost pure oxygen in place of air as an oxidizer. In this case, the flue gas comprises a higher proportion of carbon dioxide, for example about 35% by volume (about 65% by volume of water and traces of nitrogen and oxygen). This is advantageous both for the efficiency of decarbonation and for the concentration effect of the carbon dioxide at the outlet of the decarbonation unit.

Furthermore, the flue gas also usually contains small amounts of additional compounds, including sulfur compounds, fluorinated or chlorinated. These compounds tend to be captured in the water during the decarbonation step which avoids their direct discharge into the atmosphere. In addition, some of these compounds contribute to the acidification of water and thus improve the decarbonation yield.

These include sulfur dioxide, which dissolves in water as sulfuric acid which itself generates sulfate ions. Likewise hydrochloric acid or hydrofluoric acid help to acidify the water. The lower the pH, the more dissolved carbon dioxide tends to be released from the water and into the gas phase. On the other hand, the ionic species generated by the other acid components of the flue gas (SO ₄ ^{2 ~} , CI ^" , F ^" ...) tend to remain stable in the water and help to keep the water close to the water. neutrality, given their low proportion to the majority of carbon dioxide.

According to a particular embodiment, in order to improve the efficiency of the decarbonation, it is possible to provide a humidification step of the gas composition comprising carbon dioxide prior to its contact with the water to be treated. This humidification can consist of a simple degassing of the gaseous composition through a reserve or a stream of water, in order to add saturation water in the gaseous composition. Thus, the carbon dioxide is partially dissolved even before it comes into contact with the water to be treated, which improves the kinetics of the reaction.

The gas collected at the outlet of the decarbonation unit 6 in the emitted gas recovery line 7 can be discharged into the atmosphere, or preferably treated, in particular to recover the concentrated carbon dioxide that it contains. For this purpose, it is possible in particular to use a method capture of carbon dioxide, post-capture type by washing with an amine-based solution or directly repressing this gas for transport and storage.

Preferably, the water content of carbonates and bicarbonates at the inlet of the boiler 8 is less than or equal to 1 ppm. If the decarbonation step described above is not sufficient to ensure that the water content of carbonates and bicarbonates is sufficiently low, additional treatments are provided to further reduce the carbonates and bicarbonates content. Similarly, if the content of silica, calcium, magnesium, sulphates or other inorganic contaminants must be reduced before arrival in the boiler 8, additional treatment of the water is provided with means for treating the contaminants. minerals 4.

Said complementary treatment of water may comprise:

the passage of water over an ion exchange resin, in particular to reduce the hardness of the water (content of calcium and magnesium ions);

an injection of acid (for example hydrochloric acid) and a degassing of the carbon dioxide emitted, in order to complete the decarbonation described above;

- softening of the water by lime injection, in order to complete the decarbonation described above;

reverse osmosis treatment;

- evaporation treatment;

the addition of crystallization agents and the recovery of crystallized species, by decantation or by means of ceramic membranes, for example as described in applications WO 2009/029651 and WO 2009/029653;

the addition of silica deposition inhibitors, for example as described in application CA 2475048.

According to one embodiment, the purge water from the boiler 8 is discharged into the environment, possibly after separation of the suspended solids; alternatively, this purge water can be recycled via the purge line 14 to the water supply system 13, after separation of suspended solids by evaporation / crystallization and / or by decantation. This is particularly advantageous when using silica deposition inhibitors, as described in detail in WO 2009/071981. According to a preferred embodiment, the circulating water of the water supply system 13 is partially (or mainly) recycled water, that is to say obtained by condensation of the steam generated in the boiler 8, after using said vapor. In this case, the water supply pipe 1 is a water recycling pipe 1. A supply of complementary water 5, for example fresh water taken from the environment, is then generally provided. Depending on the chemical composition of this water, some treatments may be unnecessary for this water, and the complementary water supply 5 is connected to a location chosen accordingly in the water supply system 13. Typically, the arrival 5 is connected downstream of the skimming unit 2 and the de-oiling unit 3, as shown in FIG. Hydrocarbon extraction

The method and installation described above for steam generation can be used in all situations where steam generation is useful. For example, they can be used in the context of petroleum refining, to perform functions of heating, cleaning or even electrical generation. But according to a preferred embodiment, they are used for the implementation of a method, respectively in the context of an installation, hydrocarbon extraction in a subterranean formation.

In this case, the steam produced is injected into the formation by at least one injection well. The vapor mobilizes the hydrocarbons contained in the formation, such as heavy oils or hydrocarbons contained in the oil sands, which are recovered by at least one collection well (which may be identical to or different from the injection well). ).

The extraction of hydrocarbons can thus be carried out in particular by steam assisted gravity drainage (SAGD) or by steam drainage or by cyclic stimulation by steam.

The produced water is also recovered in the collection well. Generally, the hydrocarbons and water produced are mainly in the form of a water / oil emulsion. The emulsion is separated into a hydrocarbon fraction and an aqueous fraction according to techniques known in the art. The hydrocarbon fraction undergoes downstream treatment steps, while the aqueous fraction can be reused to supply the boiler feed water. EXAMPLES

The following examples illustrate the invention without limiting it.

Example 1 - experimental device

A production water from an underground formation is treated in a laboratory pilot and according to the invention, said water being intended to supply a boiler. The water has the following characteristics:

Conductivity at 25 ° C: 841 mS / m

pH: 8.05

Measuring temperature: 20.1 ° C

Suspended matter: 360 mg / L

Total organic carbon: 21 1, 4 mg / L

Humidity: 99.32% (wt)

Mercaptans: 1 ppm

Hydrogen sulphide: <1 ppm

Alkalinity: 42.5 meq / L

Silicon: 12.5 mg / L

Manganese: <20 pg / L

Boron: 14.4 mg / L

Strontium: 3.2 mg / L

Aluminum: <20 pg / L

Barium: 2.05 mg / L

Calcium: 15.00 mg / L

Copper: <10 Mg / L

Iron: <20 Mg / L

Magnesium: 28.7 mg / L

Potassium: 46.9 mg / L

Sodium: 2021, 0 mg / L

Lithium: 0.32 mg / L

Ammonium: 7.90 mg / L

Chlorides: 2093 mg / L

Bromides: 9.2 mg / L

Phosphates: <0.5 mg / L Sulphates: <0.5 mg / L

Fluorides: <0.1 mg / L

HCO ₃ : 2.6 g / L

CO ₃ : <0.5 mg / L

The decarbonation of the water is carried out in a sealed jacketed reactor provided with a water heating system.

As a source of gaseous composition, a gas cylinder filled with a mixture comprising 10% carbon dioxide and 90% nitrogen (model of combustion gas obtained with normal combustion) is used.

The gas flow from the bottle is regulated with a pressure reducer and a needle valve and measured with a film flow meter. The gas from the bottle passes into a 100 ml container filled with distilled water and kept at 60 ° C to humidify it. Then the gas arrives at the bottom of the reactor, where it is dispersed in water (500 mL) with a sintered disc. Magnetic stirring is performed to facilitate the reaction.

The effectiveness of water decarbonation is assessed by measuring the pH at the beginning, at the end of the experiment, and during the experiment. A peristaltic pump is provided for the recirculation of water, to allow continuous pH measurement. The pH meter is set at the operating temperature.

A gas collection pipe is connected to the reactor cover and connected to a film flow meter that indicates if carbon dioxide is being produced.

Before the start of the reaction, the reactor is heated to the operating temperature, before filling it with water. Once the reactor is at the correct temperature, water is added (after degassing) and the reactor is sealed. The pump is turned on, and the pH is expected to stabilize. Then the gas bottle is opened, and the gas flow is adjusted by means of the valves, controlling it with the flowmeter. The magnetic stirring is started. The pH is noted every minute or every 5 minutes during the first hour, then every 10 or 15 minutes thereafter. The pH is also noted before reaction (after degassing with nitrogen) and after reaction and degassing at room temperature.

Example 2 - results

FIG. 2 represents the evolution of the pH during the reaction, for respective gas flow rates of 10 mL / min (triangles), 50 mL / min (squares) and 100 mL / min (circles), at an operating temperature of 60 ° C. It is found that the reaction is even faster than the flow of CO ₂ is important.

FIG. 3 represents the concentration of bicarbonates (in mol / L) determined as a function of the pH, before the decarbonation reaction (checkered bars), at the end of the decarbonation reaction (white bars) and at the end of the decarbonation reaction after degassing (black bars) to remove dissolved CO ₂ .

Different situations are illustrated:

- A and B: temperature of 90 ° C and flow rate of 10 mL / min;

- C: temperature of 90 ° C and flow rate of 100 mL / min;

- D: temperature of 60 ° C and flow rate of 100 mL / min;

- E: temperature of 60 ° C and flow rate of 50 mL / min;

- F: temperature of 60 ° C and flow rate of 10 mL / min.

These results confirm that the invention substantially reduces the carbonate / bicarbonate content in water.

Claims

A method of water treatment and steam production comprising:

supply of a feed water containing carbonate and / or bicarbonate ions;

- the treatment of the feed water;

feeding a boiler with the treated feed water;

- steam generation in the boiler;

The method of claim 1, wherein the boiler produces a flue gas which provides the gaseous composition comprising carbon dioxide.

Process according to claim 1 or 2, wherein the boiler operates in oxy-fuel combustion.

Method according to one of claims 1 to 3, wherein the contacting of the feed water with the gaseous composition is carried out at a temperature greater than or equal to 60 ° C, preferably greater than or equal to 70 ° C more preferably greater than or equal to 80 ° C, and most preferably 85 ° C to 95 ° C.

Process according to one of Claims 1 to 4, in which the gaseous composition comprises at least 5% by volume of carbon dioxide, preferably at least 10% by volume of carbon dioxide, more preferably at least 20% by weight. in volume of carbon dioxide, and ideally at least 35% by volume of carbon dioxide.

The process according to one of claims 1 to 5, wherein the treatment of the feedwater also comprises: - skimming of water; and or

- the deoiling of the water; and or

the treatment of mineral contaminants contained in the water by:

^■ reverse osmosis water treatment; and or

^■ water treatment by evaporation; and or

^■ Injection silica deposition inhibiting agents.

Steam production plant comprising:

- a boiler (8);

- a water supply system (13) connected to the inlet of the boiler (8);

a steam withdrawal line (9) connected at the outlet of the boiler (8);

the water supply system (13) comprising a water decarbonation unit (6), which comprises means for contacting the water with a gaseous composition comprising carbon dioxide.

Plant according to claim 7, comprising:

- A combustion gas withdrawal line (10) connected to the output of the boiler (8) and feeding the decarbonation unit (6).

Plant according to claim 7 or 8, wherein the decarbonation unit (6) comprises:

- a water storage container;

means for recovering emitted gas (7).

10. Installation according to claim 7 or 8, wherein the means for bringing water into contact with a gaseous composition comprising carbon dioxide comprises a tray or packed column and / or a cyclone device and / or a device ejector and / or venturi.

11. Installation according to one of claims 7 to 10, wherein the water supply system (13) comprises:

- a frothing unit (2); and or

- a deoiling unit (3); and or

means for treating inorganic contaminants (4), comprising:

an ion exchange resin; and or

^■ a reverse osmosis unit; and or

■ an evaporation unit; and or

^■ the injection means of silica scale inhibitors. 12. Installation according to one of claims 7 to 11, wherein the vapor withdrawal pipe (9) is connected to an inlet of an injection well disposed in a subterranean formation containing hydrocarbons. 13. Installation according to one of claims 7 to 12, wherein the water supply system (13) is fed at least partially by a water recycle line (1), connected at the output of a system of water water recovery from a hydrocarbon production facility.

14. Installation according to one of claims 7 to 13, comprising a purge pipe (14) connected at the outlet of the boiler (8), said purge line (14) optionally supplying the water supply system (13).

A method of extracting hydrocarbons in a subterranean formation, comprising:

the production of steam according to the process of one of claims 1 to 6;

the recovery of hydrocarbons and production water in at least one extraction well disposed in the underground formation; and

de-oiling of the production water and the use of de-oiled production water as feed water in the steam production process.