FR3053690A1 - STABILIZATION OF FOAMS WITH CLAY PARTICLES - Google Patents

Abstract

The invention relates to a method for forming a stabilized foam adapted especially for the enhanced recovery of oil, by expansion of a foaming composition with at least one gas and / or water vapor, wherein said foaming composition comprises, in an aqueous medium: a surfactant or a mixture of surfactants suitable for forming a foam, under the effect of the introduction of gas and / or steam, and clay particles. The formed foam is advantageously subjected to a thermal treatment step, subsequent to or simultaneous with its formation, at a temperature above the temperature of the thermolysis of said surfactant or mixture of surfactants.

Description

Holder (s): RHODIA OPERATIONS Simplified joint-stock company, IFP ENERGIES NOUVELLES Public establishment.

Extension request (s)

Agent (s): RHODIA OPERATIONS.

PA) STABILIZATION OF FOAMS BY CLAY PARTICLES.

FR 3 053 690 - A1 (5 /) The invention relates to a process for forming a stabilized foam suitable in particular for enhanced recovery of petroleum, by expansion of a foaming composition with at least one gas and / or steam. of water, wherein said foaming composition comprises, within an aqueous medium:

a surfactant or a mixture of surfactants capable of forming a foam, under the effect of the introduction of gas and / or steam; and

- clay particles.

The foam formed is advantageously subjected to a heat treatment step, subsequent to or simultaneous with its formation, at a temperature higher than the thermolysis temperature of said surfactant or mixture of surfactants.

STABILIZATION OF FOAMS BY CLAY PARTICLES

The present invention relates to aqueous foams which are in particular usable for the enhanced recovery of crude oil in underground formations, and more particularly to the problems of stability of the foams in such cases of enhanced oil recovery.

During the extraction of petroleum from a hydrocarbon reservoir (petroleum reservoir such as a rock formation, consolidated or not, or a sand, for example), according to a first stage called "primary recovery", petroleum is driven out of the tank via a production well by the overpressure prevailing naturally within the tank. This primary recovery only gives access to a small quantity of the oil contained in the reservoir, typically of the order of 10 to 15% at most.

To allow further extraction of the oil following this primary recovery, so-called "secondary" production methods are used, when the reservoir pressure becomes insufficient to move the oil still in place. Typically, a fluid is injected (re-injection of the water produced diluted or not, injection of sea or river water, or injection of gas, for example) into the hydrocarbon tank, with a view to exerting within the tank an overpressure capable of entraining the oil towards the production well (s). A common technique in this context is the injection of water (also known as flooding or “waterflooding”), in which large volumes of water are injected under pressure into the reservoir via injector wells. The injected water entrains part of the oil it encounters and pushes it towards one or more producing wells. Secondary production methods such as water injection, however, only extract a relatively small part of the hydrocarbons in place (typically around 30%). This partial sweeping is due in particular to the trapping of the oil by capillary forces, to the differences in viscosity and density existing between the injected fluid and the hydrocarbons in place, as well as to heterogeneities on micro- or macroscopic scales (scale pores and also tank scale).

To try to recover the rest of the oil, which remains in the underground formations at the end of the implementation of the primary and secondary methods of production, it has been proposed different techniques called "enhanced oil recovery" (or enhanced recovery (or improved) of RAH hydrocarbons), or even "EOR" (for "Enhanced OU Recovery"),

Examples of EOR techniques include, but are not limited to, methods employing the formation of foam, which are intended to entrain entrained oil trapped in pore constrictions.

In particular in the case of so-called “heavy” oils, which are particularly viscous, so-called thermal EOR methods consisting in heating the oil to facilitate its flow have been developed, which advantageously use foams. Examples of thermal EOR methods include, for example, so-called SAGD recovery methods (for English: "Steam Assisted Gravity Drainage"), CSS (for English : “Cyclic Steam Stimulation >>: cyclic stimulation by steam),“ Steam Flooding >> (or “flooding >> by steam,), or even air injection processes, in particular those called type LTO (for English: “Low Temperature Oxydization”: oxidation at low temperature where air is used to generate, by combustion of light oils, a combustion gas which induces displacement of the oil) or ISC (for English: "ln-situ

Combustion >>: in situ combustion operated at a higher temperature than the LTO where effective combustion is carried out capable of generating heat, typically making it possible to reduce the viscosity of heavy oils and therefore improve their displacement, this method being able to produce water vapor). In all these so-called thermal methods, water vapor and / or other gases introduced and / or generated in situ are used. In this context, the use of foams allows better control of the movement of these gases and ultimately improves their efficiency. These foams are generated by the expansion of water vapor or the gases used from a foaming composition.

The present invention relates to foams which can be used for these methods of enhanced oil recovery, which are typically formed and used under relatively extreme conditions within underground formations (high temperature, pressure, pH, salinity, etc.). One problem encountered with these foams is that of their stability under these conditions. In particular, a number of surfactants tend to lyse under these conditions, in particular under the effect of temperature and pH.

An object of the present invention is to provide a method of foam formation improving their stability.

To this end, it is proposed according to the present invention to use a particular agent for stabilizing the foam, namely clay particles, the work of the inventors of which has now made it possible to demonstrate that they allow not only good stabilization, in particular at high temperature, but also other advantages described in more detail below.

Thus, according to a first aspect, the subject of the present invention is a process for forming a stabilized foam comprising:

a expansion step of a foaming composition by means of an expansion fluid formed by at least one gas and / or water vapor, where said foaming composition comprises, within an aqueous medium:

a surfactant or a mixture of surfactants capable of forming a foam, under the effect of the introduction of said expansion fluid; and

- clay particles;

preferably, a step of thermal treatment of the foam formed, which may be subsequent to or simultaneous with the aforementioned step of forming the foam by expansion, at a temperature higher than the thermolysis temperature of said surfactant or mixture of surfactants.

Typically, the swelling fluid used in the process of the invention contains water vapor, optionally in admixture with a gas or mixture of gases such as nitrogen. In this case, the foam is designated by "steam foam". Other foams can nevertheless be envisaged according to the invention, which are expanded by an expansion fluid that does not contain water vapor (foam based on air for example, or based on another gas).

The thermal expansion and thermal treatment steps of the process of the invention can typically be carried out as part of an oil extraction operation, in particular enhanced oil recovery. In this context, the stabilized foam formed is used for the extraction of hydrocarbons, advantageously in an underground formation where the conditions for thermolysis of said surfactant or mixture of surfactants are met. When it is used for the extraction of hydrocarbons, the process of the invention is typically carried out (i) by injecting the foaming composition into an underground formation where the temperature is between 30 to 350 ° C., and preferably at a temperature higher than the thermolysis temperature of said surfactant or mixture of surfactants; and (ii):

- By co-injecting into said underground formation all or part of the expansion fluid together with the foaming composition;

and or

- by forming in situ all or part of the expansion fluid in said underground formation into which the composition is injected, typically by forming hydrocarbon combustion gases and / or water vapor in the underground formation (for example according to the LTO or ISC techniques mentioned above).

Whatever the nature of the expansion fluid used, the process of the invention, which specifically implements the clay particles, leads to the formation of a particular foam, of gelled type. The aqueous foam formed during the expansion step can be described as a particular heterogeneous medium which comprises a plurality of gas bubbles joined together, separated from each other by liquid films, called lamellae, which are based on the foaming composition. Without wishing to be linked to a particular theory, it can be considered that the clay particles present within the lamellae are organized in a network and form there a microstructure of the physical gel type which confers interesting rheological properties on the fluid constituting the lamellae that of a fluid with a flow threshold which makes it possible to slow down, even to inhibit, the phenomena of water drainage out of the lamellae and therefore to increase the resistance of the foam to coalescence and to ripening.

The heat treatment, when carried out in the process of the invention (which is most often unavoidable in the case of petroleum extraction), induces a lysis of all or part of the surfactants which does not call into question the stabilization by clay particles. In other words, when the process of the invention comprises a heat treatment which lyses all or part of the surfactants, it makes it possible to obtain a stabilized foam which has the advantage of containing a reduced amount of surfactants. This reduction in the surfactant content (“replaced” in some way in whole or in part by clay particles) has interesting repercussions: on the one hand, it makes it possible, in general, to limit any potential “pollution” underground formations by surfactants, which constitutes an advantage in terms of repercussions on the environment; on the other hand, and more fundamentally, it leads to a reduction in the content of surfactants in the water / hydrocarbon mixtures extracted from the underground formation, which ultimately allows better separation of the hydrocarbons contained in these mixtures. In fact, the more the water / hydrocarbon mixture is rich in surfactants, the more difficult it is to separate this mixture, given the formation of an emulsion which is all the more stable as there are surfactants. The clay particles have the advantage of leading to effective stabilization of the foam due to their effect on rheology, but not to stabilization of the water / hydrocarbon emulsions recovered in fine.

The work which has been carried out by the inventors in the context of the present invention has also made it possible to highlight that the foam stabilization effects described above are observed even when the foam is formed in a medium comprising species salines. This opens the possibility of forming mosses according to the invention from any source of water available near the place of drilling (sea water for example) or even to form mosses in most underground formations. .

Different preferred embodiments of the invention will now be described in more detail.

Clay particles

The clay used in the context of the present invention is a synthetic or natural clay. It can for example be a bentonite, a hectorite or a montmorillonite. Advantageously it is a hectorite.

The clays according to the invention can optionally be treated for example with compounds of quaternary ammonium type. Untreated clays can however also be used.

According to an interesting embodiment, the clay used according to the invention is a laponite, typically synthetic. As a non-restrictive example of laponite suitable for the invention, reference may be made to Laponite XLG® available from the company Safic Alcan, which is the subject of the examples given at the end of this description.

Whatever its exact nature, clay is used in the compositions of the invention in the form of "particles", namely in the form of small dispersed objects, typically less than a millimeter, and generally much less. The clay particles consist of more or less aggregated elementary sheets whose aggregation state can be measured in particular by transmission electron microscopy (Cryo MET) or by light scattering techniques which give access to the hydrodynamic diameter means of the particles in the foaming composition.

In particular in order to obtain the highest possible stabilizing effect, it is preferable that the foaming composition used according to the invention comprises at least 0.001%, typically at least 0.01%, for example at least 0.05% by mass relative to to the total mass of the foaming composition. Interesting results are notably obtained when the clay content is greater than 0.1%, for example at least equal to 0.15% by mass relative to the total mass of the foaming composition. In general, the more the amount of clay increases, the more the stabilizing effect increases.

It should however be noted that clays have a noticeable thickening character and that, for most applications, it is preferable to limit their content in order to avoid obtaining excessively high viscosities. In the context of the present invention, it is preferable that the clay content in the foaming composition remains less than or equal to 5%, and more preferably less than 1%, or even 0.5% by mass relative to the total mass of the foaming composition, in particular for applications in the field of petroleum extraction.

Thus, according to an advantageous embodiment, well suited in particular to the use of the foams according to the invention for enhanced oil recovery operations, the foaming composition used comprises clay with a content between 0.01 and 1% in mass relative to the total mass of the foaming composition, for example between 0.02 and 0.5%, in particular between 0.05 and 0.2%.

Surfactants usable in the foaming composition

Any surfactant or surfactant system capable of forming a foam can be used according to the invention. Advantageously, the surfactants will also be chosen so that they can be degraded in whole or in part after or during the formation of the foam. For this purpose, it will be interesting to choose surfactants degrading at the lowest possible temperature, in particular at a temperature less than or equal to 250 ° C., or even at a temperature less than or equal to 200 ° C., or even less than or equal to 150 ° C. .

Whatever the nature of the surfactants, in the foaming compositions used in the present invention, the mass ratio of surfactant (s) / clay is preferably between 1 and 2000.

Furthermore, the foaming composition preferably comprises from 0.005 to 5% of surfactants or of mixture of surfactant, preferably between 0.1 and 1%, by mass relative to the total mass of the foaming composition.

According to a particular embodiment, the surfactant or mixture of surfactants present in the foaming composition used according to the invention comprises a surfactant of the alkyl sulfate or alkyl ether sulfate type where the alkyl chain advantageously comprises from 8 to 18 carbon atoms, for example from 10 to 16, such as for example sodium Laureth sulfate. An example of such a surfactant is Rhodapex® ESB-70 / A2 available from the company Solvay illustrated in the examples given below. Typically, a surfactant of the alkyl sulfate or alkyl ether sulfate type can be used in an amount of 0.1 to 1% by mass relative to the total mass of the foaming composition.

Alkyl sulphate or alkyl ether sulphate are particularly interesting because they are both good foaming agents and they are generally quite thermally sensitive. Typically, by forming a foam from these agents at a temperature above 100 ° C., in particular at 150 ° C., for example of the order of 200 ° C., the formation of the foam and the thermolysis according to invention. Other interesting surfactants that degrade in the same temperature ranges are:

- sulfosuccinates

- sulfosuccinamates,

- taurates

- amine oxides

- alkylamido alcohols

- alkyl polyglucosides

- quaternary alkylammoniums

- alkyl ampho dipropionates

- mixtures of two or more of these compounds and mixtures of these compounds with alkyl sulfates or alkyl ether sulfate.

According to a possible embodiment, the surfactant or mixture of surfactants present in the foaming composition used according to the invention comprises a zwitterionic surfactant, in particular an alkylamidobetaine, an alkylamidohydroxysultaine, an alkylbetaine, or an alkylhydroxysultaine, where the alkyl chain advantageously comprises from 8 with 18 carbon atoms, such as for example cocoamidohydroxypropyl sultaine illustrated in the examples, which are fairly thermally sensitive.

Mixtures of interesting surfactants according to the invention, in particular when it is desired to obtain a thermal degradation effect at relatively low temperature (typically below 250 ° C., for example between 150 and 200 ° C.) with a good foaming effect are the mixtures of alkyl ether sulfate and zwitterionic surfactants of the aforementioned type, in particular of the amido type; and mixtures of alkyl ether sulfate with alkyl poly glycoside.

According to another embodiment, the surfactant or mixture of surfactants present in the foaming composition used according to the invention comprises a surfactant of the alkyl sulfonate type, where the alkyl chain advantageously comprises from 8 to 18 carbon atoms, for example from 10 to 16, such as for example C14-16 alfa olefin sulfonate. These agents are good foaming agents, but generally require higher temperatures to be thermally degraded (typically at least 250 ° C). the alkyl sulfonates are preferably used in admixture with alkyl sulfates.

According to a particular aspect, the invention relates to foaming compositions for implementing the process of the invention, comprising:

- At least one surfactant, preferably degrading at a temperature less than or equal to 250O, more advantageously less than or equal to 200O, preferably of one of the aforementioned types; and

- particles of clay.

The example below illustrates a non-limiting embodiment of the invention and some of its advantages.

EXAMPLE

In this example, the stability was tested for foams produced at 200 ° C. and at 25 bars (2.5 × 10 ^e Pa) from different foaming solutions including clay particles.

By way of comparison, foams obtained under the same conditions with the same compositions but devoid of clay were also tested.

The stability of each foam was evaluated by measuring its half-life time according to the following protocol:

In a tubular glass bottle, equilibrated at the working pressure of 25 bars (2.5 × 10 ^e Pa) and at the working temperature of 200 ° C., previously filled with the foaming composition, it was co-injected through a frit ensuring the role of aerator:

- foaming solution brought to 200 ° C and injected at working pressure via a high-pressure liquid pump with a constant flow rate of 3.2 mL / min,

- nitrogen brought to 200 ° C and injected at working pressure via a high pressure gas pump with a constant flow rate of 4.8 mL / min

The foam formed at the outlet of the sinter is injected into the bottle from above. A tube immersed in the bottle and opening at the bottom of the latter ensures an exit of the liquid overflow from below. The tube that opens on one side to the bottom of the tube has been connected at its other end to a back pressure regulator, which keeps the pressure constant in the bottle.

The gas used is nitrogen to avoid artifacts related to vapor recondensation.

A CCD camera allows the temporal acquisition of the images of formed mosses which are observed through the transparent tube. The analysis of the images thus makes it possible to follow the evolution of the height of foam as a function of time. At the start of foam injection, the foam height increases and reaches a maximum (initial foam volume) then the foam height decreases over time.

The half-life time measured for the foams formed with each of the foaming compositions tested in the present example is the time at the end of which the foam height is equal to half of the initial foam height (the section of the tube being constant, this also corresponds to the time it takes for the initial volume of foam to decrease by half).

The foaming compositions tested, the compositions of which are given below, comprise the following products:

Surfactants:

Rhodapex® ESB-70 / A2 (alkyl ether sulfate - source: Solvay) Mackam® CBS (sulfobetaine - source: Solvay)

- Clay:

Laponite XLG ® (source: Safic Alcan)

Each foaming solution was prepared as follows:

The surfactant is dissolved in demineralized water at a total mass concentration of 0.5% by mass of active material, then stirred for 24 hours at room temperature.

Except in the case of comparative compositions (controls), clay is added to the solution; in all cases, the pH is adjusted to pH = 7 by adding citric acid and the solution is again stirred for 24 hours.

The table below gives the details of the foaming compositions tested (nature of the surfactant and content in the composition, in percentage by mass relative to the total mass of the composition - clay content (Laponite XLG) in percentage by mass relative to the total mass of the composition) and the half-life time (t _1/2 ) measured for each of them.

Composition foaming Surfactant clay ti / ₂ (min) Witness 1 Rhodapex ESB-70 / A2 - 0.5% - 8 C1.1 Rhodapex ESB-70 / A2 - 0.5% 0.05% 34 C1.2 Rhodapex ESB-70 / A2 - 0.5% 0.1% 38 C1.3 Rhodapex ESB-70 / A2 - 0.5% 0.125% 94 Witness 2 Mackam CBS - 0.5% - 3 C2 Mackam CBS - 0.5% 0.125% 20

Under the experimental conditions, the surfactants used degrade by thermolysis, which is not the case with clays. Whatever the nature of the surfactants, the addition of clay improves stability.

Claims (10)

1. Method for forming a stabilized foam comprising: a expansion step of a foaming composition by means of an expansion fluid formed by at least one gas and / or water vapor, where said foaming composition comprises, within an aqueous medium: - a surfactant or a mixture of surfactants capable of forming a foam, under the effect of the introduction of said swelling fluid; and - clay particles; - Preferably, a step of heat treatment of the foam formed, which may be subsequent or simultaneous with the formation of the foam, at a temperature higher than the thermolysis temperature of said surfactant or mixture of surfactants. 2. The method of claim 1, wherein the stabilized foam is used for the extraction of hydrocarbons, and wherein the foaming composition is injected into an underground formation where the temperature is between 30 to 350 O, and preferably at a temperature higher than the thermolysis temperature of said surfactant or mixture of surfactants; and - In lequektout or part of the expansion fluid is co-injected into said underground formation together with the foaming composition; and or - All or part of the expansion fluid is formed in situ in said underground formation where the composition is injected, typically by forming hydrocarbon combustion gases and / or water vapor in said underground formation. 3. Method according to claim 1 or 2, wherein the clay is a laponite. 4. Method according to one of the preceding claims, wherein the foaming composition comprises clay at a content of 0.001 to 5%, preferably between 0.01 and 5% by mass relative to the total mass of the foaming composition . 5. Method according to one of the preceding claims, wherein the surfactant or mixture of surfactants comprises an alkyl! ether sulfate 6. Method according to one of the preceding claims, wherein the surfactant or mixture of surfactants comprises a zwitterionic surfactant, in particular an alkylamidobetaine, an alkylamidohydroxysultaine, an alkylbetaine, or an alkylhydroxysultaine 7. Method according to one of the preceding claims, wherein the surfactant or mixture of surfactants comprises an alkyl sulfonate, preferably in admixture with an alkyl ether sulfate. 8. Method according to one of the preceding claims, wherein the mass ratio surfactant (s) / clay is between 1 and 2000 9. Method according to one of the preceding claims, wherein the foaming composition comprises from 0.005 to 5% of surfactants or mixture of surfactant, by mass relative to the total mass of the foaming composition. 10. - Foaming composition for the implementation of the method of one of claims 1 to 9, comprising: - At least one surfactant, preferably degrading at a temperature less than or equal to 250 ° C, more advantageously less than or equal to 200 ° C; and - particles of clay.