WO2018007305A1

WO2018007305A1 - Stabilisation of foams by clay particles

Info

Publication number: WO2018007305A1
Application number: PCT/EP2017/066474
Authority: WO
Inventors: Mikel Morvan; Max Chabert; Amandine CUENCA
Original assignee: Rhodia Operations; IFP Energies Nouvelles
Priority date: 2016-07-08
Filing date: 2017-07-03
Publication date: 2018-01-11
Also published as: FR3053690A1; CA3030057A1; EP3481912A1; FR3053690B1

Abstract

The invention concerns a method for forming a stabilised foam suitable, in particular, for enhanced oil recovery, by expanding a foaming composition by means of at least one gas and/or steam, in which said foaming composition comprises, within an aqueous medium: - a surfactant or a mixture of surfactants suitable for forming a foam, under the effect of the introduction of the gas and/or the steam; and - clay particles. The foam formed is advantageously subjected to a heat treatment step, subsequent or simultaneous to the formation of same, at a temperature higher than the thermolysis temperature of said surfactant or mixture of surfactants.

Description

STABILIZATION OF FOAMS WITH CLAY PARTICLES

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

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

To allow oil extraction to continue 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 diluted or non-diluted produced water, injection of sea or river water, or injection of gas, for example) into the hydrocarbon reservoir, with a view to exerting a positive overpressure in the tank to drive the oil to the production well (s). A common technique in this context is the injection of water (also referred to as flooding or "waterflooding"), in which large volumes of water are injected under pressure into the reservoir via injection wells. The injected water causes some of the oil it meets and pushes it to one or more producing wells. However, secondary production methods such as water injection can extract only a relatively small portion of the hydrocarbons in place (typically around 30%). This partial sweep is due in particular to the trapping of the oil by the capillary forces, to the viscosity and density differences existing between the injected fluid and the hydrocarbons in place, as well as to heterogeneities at micro- or macroscopic scales (scale pores and also tank scale).

To try to recover the remaining oil, which remains in the underground formations after the implementation of primary and secondary production methods, it has been proposed various techniques called "enhanced oil recovery" (or enhanced recovery). (or improved) hydrocarbons RAH), or even "EOR" (for English "Enhanced OR Recovery"), Among the techniques of the EOR are, among others, methods employing the formation of foams, which aim at ensuring entrainment of the oil entrapped in the constrictions of pores.

Particularly in the case of so-called "heavy" oils, particularly viscous, so-called thermal EOR methods of heating the oil to facilitate its flow have been developed, which advantageously implement foams. As examples of thermal EOR methods, the so-called SAGD (Steam Assisted Gravity Drainage), CSS (for example: "Cyclic Steam Stimulation", "Steam Flooding", or even air injection methods, especially those of the LTO type (for the first time). English: "Low Temperature Oxydization": low-temperature oxidation where air is used to generate, by burning light oils, a combustion gas that induces a displacement of oil) or ISC (for English: " In-situ Combustion: In-situ combustion operated at a higher temperature than the LTO where effective combustion is achieved to generate heat, typically reducing the viscosity of heavy oils and thus improving their displacement, this method being e can produce water vapor). In all these so-called thermal methods, water vapor and / or other gases introduced and / or generated in situ are employed. In this context, the use of foams allows better control of the movement of these gases and ultimately improve their efficiency. These foams are generated by the proliferation of water vapor or gases used from a foaming composition.

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

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

For this purpose, it is proposed according to the present invention to employ a particular agent for the stabilization of the foam, namely clay particles, whose work the inventors have now made it possible to highlight that they allow not only good stabilization, especially at high temperature, but also other advantages described in more detail below.

Thus, according to a first aspect, the present invention relates to a method of forming a stabilized foam comprising:

^■ an expansion step of a foamable composition by means of an expansion fluid formed by at least one gas and / or steam, wherein said foamable composition comprises, in 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 heat treatment step of the foam formed, which may be subsequently or simultaneously with said step of the foam forming expansion at a temperature higher than the temperature of thermolysis of said surfactant or surfactant mixture.

Typically, the expansion fluid employed in the process of the invention contains water vapor, optionally mixed with a gas or mixture of gases such as nitrogen. In this case, the foam is referred to as "steam foam". Other foams are nevertheless conceivable according to the invention, which are overrun by an expansion fluid containing no water vapor (air-based foam for example, or based on another gas).

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

co-injecting into said subterranean 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 subterranean formation where the composition is injected, typically by forming hydrocarbon combustion gases and / or water vapor in the subterranean formation (for example according to LTO or ISC techniques mentioned above). Whatever the nature of the expansion fluid used, the method of the invention, which specifically implements the clay particles, leads to the formation of a particular foam, 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 contiguous to one another, separated from each other by liquid films, which are called lamellae, which are based on the foaming composition. Without wishing to be bound to a particular theory, it can be considered that the clay particles present within the lamellae are organized into a network and form a microstructure of the physical gel type which confers interesting rheological properties on the constituent fluid of the lamellae, typically that of a fluid with a threshold of flow which makes it possible to slow, or even to inhibit, the phenomena of drainage of water out of the lamellae and thus 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 a petroleum extraction), induces 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 of the surfactant content ("replaced" in some way in whole or in part by clay particles) has interesting repercussions: on the one hand, it allows, in a general way, to limit any potential "pollution" of the formations underground by tensiocatives, which is an advantage in terms of environmental impact; on the other hand, and more fundamentally, it leads to a reduction of the surfactant content in the water / hydrocarbon mixture extracted from the formation underground, which ultimately allows a better separation of the hydrocarbons contained in these mixtures. Indeed, the more the water / hydrocarbon mixture is rich in surfactants and the more this mixture is difficult to separate in view of the formation of an emulsion that is more stable as there are surfactants. The clay particles have the advantage of leading to an effective stabilization of the foam by their effect on the rheology, but not to a stabilization of water / hydrocarbon emulsions recovered in fine.

The work carried out by the inventors in the context of the present invention has furthermore 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 salt. This opens up the possibility of forming foams according to the invention from any source of water available near the location of a borehole (seawater for example) or to form foams in most underground formations .

Various 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 may for example be a bentonite, a hectorite or a montmorillonite. Advantageously it is a hectorite.

The clays according to the invention may optionally be treated for example with quaternary ammonium compounds. 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 adapted to the invention, reference may be made to Laponite XLG® available from Safic Alcan which is the subject of the examples given at the end of the present description.

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

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

It should be noted, however, that the clays have a significant thickening character and that for most applications it is preferable to limit their content to avoid obtaining excessive 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 weight relative to the total mass of the foam. 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 foams according to the invention for enhanced oil recovery operations, the foaming composition employed comprises the clay at a content between 0.01 and 1% by weight. mass relative to the total mass of the foaming composition, for example between 0.02 and 0.5%, especially between 0.05 and 0.2%.

Surfactants that can be used in the foaming composition

Any surfactant or surfactant system suitable for forming a foam may be used according to the invention. Advantageously, the surfactants will be further selected to be able to 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 that degrade at the lowest possible temperature, especially at a lower temperature or equal to 250 ° C, or even at a temperature less than or equal to 200 ° C, or even lower than or equal to 150 ° C.

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

Moreover, the foaming composition preferably comprises from 0.005 to 5% of surfactants or of a surfactant mixture, preferably from 0.1 to 1% by weight relative to the total weight 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 tensiaoctif of alkyl sulphate or alkyl ether sulphate type where the alkyl chain advantageously comprises from 8 to 18 carbon atoms, for example from 10 to 16, such as sodium laureth sulfate. An example of a surfactant of this type is Rhodapex® ESB-70 / A2 available from the company Solvay illustrated in the examples given below. Typically, a surfactant of the alkyl sulphate or alkyl ether sulphate type may be employed at a level of 0.1 to 1% by weight relative to the total weight of the foaming composition.

The 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., especially at 150 ° C., for example of the order of 200 ° C., the formation of the foam and the thermolysis according to US Pat. invention. Other interesting surfactants that degrade in the same temperature ranges are:

- sulfosuccinates

sulfosuccinamates,

- the taurates

- amine oxides

alkylamido alcohols

alkyl polyglucosides

the quaternary alkylammoniums

alkyl ampho dipropionates mixtures of two or more of these compounds and mixtures of these compounds with alkyl sulphates or alkyl ether sulphates.

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, in which the alkyl chain advantageously comprises 8 to 18 carbon atoms, such as cocoamidohydroxypropyl sultaine illustrated in the examples, which are quite thermally sensitive. Interesting mixtures of surfactants according to the invention, in particular when it is desired to obtain a thermal degradation effect at a 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 sulphate and zwitterionic surfactants of the abovementioned type, in particular of the amido type; and mixtures of alkyl ether sulphate 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 an alkyl sulfonate tensiaoctif, in which 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 alkylsulfonates are preferably employed in admixture with alkyl sulfates.

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

at least one surfactant, preferably degraded at a temperature of less than or equal to 250 ° C, more preferably less than or equal to 200 ° C, preferably of one of the abovementioned types; and

- Clay particles. The following example illustrates a non-limiting embodiment of the invention and some of its advantages. EXAMPLE

In this example, the stability was tested for foams made at 200 ° C. and 25 bar (2.5 × 10 ⁶ Pa) from various 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 glass tubular flask, equilibrated at the working pressure of 25 bar (2.5 × 10 ⁶ Pa) and at the working temperature of 200 ° C., previously filled with the foaming composition, was co-injected through a sintered acting as a foamer:

the foaming solution brought to 200 ° C. and injected at the operating 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 the pressure of working 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 dipping into the bottle and opening at the bottom of it ensures an outlet of too much liquid from below. The tube which opens on one side at 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 the artifacts associated with the vapor recondensation.

A CCD camera allows the temporal acquisition of formed foam images observed through the transparent tube. The analysis of the images thus makes it possible to follow the evolution of the foam height as a function of time. At the start of the foam injection, the foam height increases and reaches a maximum (initial volume of foam) and the foam height decreases over time. The measured half-life time for the foams formed with each of the foaming compositions tested in the present example is the time at which the foam height is equal to half the initial foam height (the section of the tube being constant, this also corresponds to the time that the initial volume of foam to halve).

The foaming compositions tested, the compositions of which are given below, include 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 solubilized in demineralized water at a total mass concentration of 0.5% by weight 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 addition of citric acid and the solution is stirred again for 24 hours.

The following table shows the details of the foaming compositions tested (nature of the surfactant and content in the composition, in weight percentage 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 (ti _{/ 2} ) measured for each of them. Composition

Surfactant clay ti / ₂ (min) foaming

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 employed are degraded by thermolysis, which is not the case with clays. Whatever the nature of the surfactants, the addition of clay improves the stability.

Claims

1. A method of forming a stabilized foam comprising:

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

clay particles;

- Preferably, a heat treatment step of the formed foam, which may be subsequent to or simultaneous with the formation of the foam, at a temperature above the temperature of said surfactant or surfactant mixture thermolysis.

The process according to claim 1, wherein the stabilized foam is employed for hydrocarbon extraction, wherein the foaming composition is injected into a subterranean formation where the temperature is between 30 to 350 ° C, and preferably at a temperature greater than the temperature of thermolysis of said surfactant or mixture of surfactants; and wherein:

all or part of the expansion fluid is co-injected into said subterranean formation together with the foaming composition; and / or all or part of the expansion fluid is formed in situ in said subterranean formation where the composition is injected, typically forming hydrocarbon combustion gases and / or water vapor in said subterranean formation.

3. The method of 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 weight relative to the total weight of the foaming composition. .

5. Method according to one of the preceding claims, wherein the surfactant surfactant mixture 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 surfactant mixture comprises an alkyl sulphonate, preferably in admixture with an alkyl ether sulphate.

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% surfactant or surfactant mixture, by weight relative to the total weight of the foaming composition.

10. Foaming composition for carrying out the method of one of claims 1 to 9, comprising:

at least one surfactant, preferably degrading at a temperature of less than or equal to 250 ° C, more preferably less than or equal to 200 ° C; and

- Clay particles.