Method for treating a subterranean formation by injecting an aqueous gelling solution comprising an aluminate

Abstract

The invention relates to a method for sealing and / or consolidating a subterranean formation, wherein an aqueous gelling solution containing an alkaline potassium silicate solution, an acetic acid and an aluminate is prepared and subsequently injected into the underground formation.

Description

[0001] METHOD FOR TREATING AN UNDERGROUND FORMATION BY INJECTION OF A GELIFYING AQUEOUS SOLUTION COMPRISING AN ALUMINATE

[0002] technical field

[0003] The present invention relates to the field of treatment of an underground formation in order to seal and / or consolidate the underground formation and / or to seal a well, in particular in the field of geological storage of acid gases, for example carbon dioxide CO2.

[0004] The term "sealing" an underground formation refers to a process aimed at reducing the permeability of at least a portion of the underground formation, particularly with respect to a given fluid, such as oil or water. The term "consolidating" an underground formation refers to a process aimed at improving its mechanical properties. It should be noted that both of these applications can be achieved with a single process. The term "sealing" a well refers to a process aimed at sealing cracks present in the material, such as cement, that forms the well.

[0005] In various applications of underground formations, it is often useful to seal and / or consolidate the formation and / or seal a well to facilitate its subsequent use, for example, for the geological storage of acid gas. For instance, fragile or clayey soils must be consolidated to address swelling or shrinkage. As another example, water channels in soils often need to be sealed, particularly to create a preferential flow path for a fluid by reducing the permeability of adjacent areas to that fluid (the fluid could be, for example, water or oil).

[0006] Previous technique

[0007] Several methods have been developed to seal and / or consolidate underground formations.

[0008] For example, patent application EP 0597735 describes the preparation of a grout (i.e., a fluid mortar that can flow into cavities; such a grout contains solid particles) for sealing and / or consolidating soils and construction materials. Such a grout does not have a viscosity suitable for injection into an injection well to treat a deep underground formation. Furthermore, there is patent application WO 2010 / 0107219 A1, which describes a method for treating the areas surrounding acid gas storage wells. This method involves injecting a washing fluid into the rock, followed by a reactive solution adapted to react with acid gases; this reactive solution contains basic oxides. However, this method proposes the use of materials that can be expensive, can pollute the underground formation, and may require specific preparation, particularly to adjust the viscosity.

[0009] Furthermore, patent application FR 3049642 (WO 2017 / 174243) also describes a method for treating wellheads, in which a gelling aqueous solution comprising an alkaline potassium silicate solution and acetic acid is prepared and then injected into an underground formation. This gelling aqueous solution, thanks to its gelling properties, seals the wellheads in a cost-effective and low-polluting manner. However, under certain conditions, this gelling aqueous solution can undergo syneresis after the acetic acid-induced gelation. This mechanism is an evolution of the chemical bonds present in the polymers constituting the gel's structural network. The syneresis mechanism results in the expulsion of water from the gel. This expulsion of water from the gel therefore prevents the sealing and / or consolidation of the underground formation in a stable manner over time.

[0010] Summary of the invention

[0011] The present invention aims to seal and / or consolidate an underground formation and / or plug a well at depth, without contaminating the underground formation and in a stable manner over time (with a limited syneresis mechanism). To this end, the present invention relates to a method for sealing and / or consolidating an underground formation, in which an aqueous gelling solution comprising an alkaline potassium silicate solution, acetic acid, and an aluminate is prepared and then injected into the underground formation. The aqueous gelling solution seals and / or consolidates the underground formation and / or plugs a well penetrating the underground formation.The aluminate present in the aqueous gelling solution limits the syneresis mechanism, thus limiting the expulsion of water from the gel. This promotes a stable, long-term sealing and / or consolidation of the underground formation and / or prevents the well from clogging. The invention relates to a method for treating an underground formation, said formation being traversed by at least one injection well. This method involves the following steps: a) Preparing an aqueous gelling solution comprising an alkaline potassium silicate solution, acetic acid, and an aluminate; and b) Injecting said aqueous gelling solution into said underground formation through said injection well to seal and / or consolidate said underground formation.

[0012] According to one embodiment, said aluminate is selected from sodium aluminate in powder form and potassium aluminate in powder form.

[0013] According to one aspect, the gelling aqueous solution is prepared according to characteristics of the underground formation, such as porosity, permeability, surrounding temperature and / or surrounding pH.

[0014] Advantageously, a gelling aqueous solution is prepared having a viscosity between 1 and 10 cP.

[0015] In accordance with an implementation procedure, a gelling aqueous solution is prepared with a setting time of between 3 and 20 hours.

[0016] According to one option, said acetic acid has a concentration between 0.1 and 5 mol / L, preferably between 0.5 and 2 mol / L.

[0017] According to one embodiment, said alkaline potassium silicate solution comprises a silicon concentration (Si) of 0.5 to 7 mol / L, preferably from 0.5 to 3 mol / L. Advantageously, said alkaline potassium silicate solution comprises a molar ratio of silicon dioxide (SiO2) to potassium oxide (K2O) of between 0.5 and 10, preferably between 1 and 5.

[0018] According to one implementation, said aqueous gelling solution comprises between 1 and 30% by mass of acetic acid, preferably between 5 and 30%.

[0019] Advantageously, the aqueous gelling solution may comprise between 0.1 and 1% by mass of aluminate, preferably between 0.3 and 0.8%, most preferably between 0.4 and 0.6%, substantially 0.5% by mass of aluminate.

[0020] According to one feature, a washing fluid is injected from said injection well into said subsurface formation prior to the injection of said aqueous gelling solution. According to one embodiment, said treatment of the subsurface formation is a sealing of said subsurface formation, and / or a consolidation of said subsurface formation, and / or a sealing of a well in said subsurface formation.

[0021] In one embodiment, the well is a storage well, in particular for storing acid gas in the underground formation. In one aspect, the acid gas is stored prior to the injection of the aqueous gelling solution.

[0022] Advantageously, the said underground formation has a surrounding pH of less than 9.

[0023] Other features and advantages of the process according to the invention will become apparent from the following description of non-limiting examples of implementations, with reference to the figures attached and described below.

[0024] List of figures

[0025] Figure 1 illustrates different configurations of aluminum substitution in the silica gel formed within the aqueous gelling solution.

[0026] Figure 2 illustrates a comparative curve of the water fraction contained in the gel used for a process according to the prior art and for the process according to the invention.

[0027] Description of the implementation methods

[0028] The principle of the invention is based on the introduction of a solution into an underground formation to significantly reduce the permeability of the reservoir rock, and / or to consolidate it and / or to seal a well. Thus, the injected solution makes it possible, in particular, to limit or even prevent fluid leaks and / or to improve the mechanical properties of the underground formation. The term "underground formation" refers to the soil and subsoil; the depth of the underground formation can range from a few meters (for example, for soil consolidation applications under buildings or dwellings) to several kilometers (for example, for hydrocarbon well or gas storage applications).

[0029] The present invention therefore relates to a method of treating an underground formation, the underground formation being crossed by at least one injection well or injector (the well or injector can be made at a depth of a few meters to several kilometers, the depth can depend in particular on the application of the method of treating an underground formation), for which the following steps are carried out: a gelling aqueous solution comprising an alkaline solution of potassium silicate, acetic acid, and an aluminate is prepared on the surface; the gelling aqueous solution is injected from the injection well or injector into the underground formation to seal and / or consolidate the underground formation.

[0030] The treatment of the underground formation may consist in particular of sealing the underground formation and / or consolidating the underground formation and / or sealing a shaft in the underground formation.

[0031] The process according to the invention may comprise several successive steps, for example two, of injecting the aqueous gelling solution. Preferably, the injection process may comprise a single injection.

[0032] Such a gelling aqueous solution is stable and unalterable, especially when the surrounding pH (of the underground formation) is less than 9. Therefore, the process according to the invention can preferably be implemented for an underground formation having a pH less than 9, which is the case in general.

[0033] The term "gelling agent" indicates that the aqueous solution is formulated as a non-gelled, low-viscosity liquid that gels in situ; in other words, it completes its gelation once injected into the subsurface formation (the pH and shear stress within the subsurface formation promote the gelling of the aqueous gelling agent). The composition of the aqueous gelling agent is therefore chosen to form a gel after a sufficiently long period to allow the liquid to be transported from the surface to the subsurface formation. Thus, thanks to its gelling properties, the aqueous solution can fulfill its role of limiting the permeability and porosity of the subsurface formation.

[0034] The aqueous gelling solution prepared in the process according to the invention is a mineral (non-organic) solution. Furthermore, the aqueous gelling solution contains no solid particles, nor any salts other than aluminate and silicate.

[0035] An alkaline solution is a basic solution that has a pH greater than 7.

[0036] It is worth noting that silica is highly soluble in alkaline solutions, particularly those with a pH of approximately 10 and above. Furthermore, a decrease in pH causes the precipitation of silica in the alkaline solution: from a liquid phase in which the silica is in its ionic form, oligomers are created and then condense to form a gel. This gel tends to adhere to mineral surfaces by forming chemical bonds. Thus, in a porous underground formation, the injection of such substances can significantly reduce permeability and porosity, or even completely block the porous network after precipitation. In addition, the minerals precipitated by the gelling aqueous solution also form a protective layer for well equipment against stored acidic gases. Various forms of silicates exist: sodium, potassium, lithium, etc.Potassium silicate (K₂O₅Si₂) is a water-soluble silicate with the general formula K₂O₅Si₂. This silicate has the advantage of making the alkaline solution less viscous than sodium silicate (Na₂O). Therefore, potassium silicate requires less dilution, simplifying the preparation of the aqueous gelling solution. Furthermore, since alkaline silicate solutions do not contain particles, there are virtually no limits to injectivity with respect to the pore size of the porous medium in the underground formation. In particular, such a solution can be injected into compact media with nanometric pore sizes, further improving their barrier capacity. Moreover, the alkaline potassium silicate solution has the advantage of being inexpensive, costing only a few hundred euros per ton.For example, potassium silicate can be used in the commercial products Betol K 35 T™, Betol K 48 T™, Betol K 54 T™, or Betol K 28 T™ marketed by Woellner (Germany). As a non-limiting example, the composition of the potassium silicates Betol K 35 T™ and Betol K 28 T™ is described in Table 1. In this table, density, which is dimensionless, corresponds to the mass per unit volume of water.

[0037] [Table 1]

[0038] Acetic acid, also called ethanoic acid, is a simple carboxylic acid with a theoretical C2 carbon chain, analogous to ethane, with a molar mass of 60 g / mol and a molecular formula of C2H4O2 or CH3COOH. Vinegar is an example of an acetic acid solution: it can be a mixture of water and acetic acid. Unlike other acids, acetic acid has the advantage of not being polluting or dangerous, either during its preparation or when injected into underground formations.

[0039] An aluminate is a compound containing an aluminum oxyanion. The addition of aluminate does not significantly alter the viscosity of the aqueous gelling solution. Furthermore, aluminate has no environmental impact. Aluminum in the form of aluminate is preferred due to its solubility in aqueous solution (for example, pure aluminum is insoluble and therefore unsuitable for the process according to the invention). The addition of aluminum to the aqueous gelling solution generates a reaction whereby an aluminum atom substitutes a silicon atom in the silica network formed within the specific composition. The location of this substitution depends, in particular, on the pH conditions and the concentration of aluminum ions. Figure 1 illustrates, schematically and without limitation, different configurations of aluminum substitution in the silica network.The figure labeled "pure-silica stab" represents the silica network before substitution (in the absence of aluminum). Figures labeled "type (i)" through "type (iv)" represent the different configurations. The most effective configuration for limiting syneresis is "type (iv)," since aluminum replaces silica at the center of the tetrahedron, altering the length of all chemical bonds and thus limiting water expulsion from the gel.

[0040] According to one embodiment of the invention, the aluminate can be sodium aluminate (formula NaAlO2) or potassium aluminate (formula KAlO2). These aluminates are soluble in aqueous solution. Furthermore, the ionic potential of sodium and potassium is low, and consequently, these atoms attract fewer anions to form minerals and precipitate, thus allowing the formation of a precipitate-free, gelling aqueous solution. Preferably, the process according to the invention can utilize sodium aluminate. This aluminate increases the long-term impermeability of the underground formation.

[0041] In addition, preferably, the aluminate is added in powder form to the aqueous gelling solution, for example sodium aluminate powder or potassium aluminate powder.

[0042] According to one embodiment of the invention, the aqueous gelling solution is prepared at room temperature, and the products (e.g., water or powder) are preferably added gradually to the silicate solution. Thus, the step of preparing the aqueous gelling solution can be carried out by adding the aluminate to the water used to dilute the alkali silicate, before adding the acetic acid. In other words, the preparation can be carried out as follows: the aluminate is mixed with water, the potassium silicate is diluted with this water, and then the acetic acid is added, taking the temperature into account.

[0043] According to one embodiment of the invention, the composition of the aqueous gelling solution is determined essentially as a function of the temperature of the underground formation. For example, during preparation, the proportions of water and acid can be modified to adjust the gelling time while maintaining low viscosity.Indeed, the usual main constraints for the injection of solutions into an underground formation are as follows: a moderate viscosity so that the injection pressures are well below the fracturing pressures of the formation, advantageously, the viscosity of the aqueous gelling solution can be between 1 and 10 cP, and a setting time, also called gelation time, (i.e. the time required between the preparation of the solution and its gelation) sufficient to allow the injection of the solution when it is prepared on the surface, then injected into the formation, advantageously, the gelation time can be between 3 and 20 hours.

[0044] According to one embodiment of the invention, the acetic acid can have a concentration of between 0.1 and 5 mol / L, preferably between 0.5 and 2 mol / L, within the solution used for preparation. This concentration range makes it possible, in particular, to prepare the gelling solution without the risk of generating aggregates and a non-homogeneous solution. For example, the acetic acid can have a concentration of approximately 1 mol / L, that is to say, a concentration substantially identical to that of vinegar. It is the concentration of pure acid in the gelling solution that determines the gelling time. Thus, the initial silicate solution can be diluted with a larger quantity of water if a more concentrated acid is used.

[0045] According to one embodiment of the invention, the alkaline potassium silicate solution may comprise a silicon concentration (Si) of 0.5 to 7 mol / L, preferably 0.5 to 3 mol / L. This concentration range makes it possible, in particular, to obtain stable, irreversible gels. For example, a commercial alkaline potassium silicate solution may comprise a silicon concentration of between 4 and 5 mol / L, approximately 4.7 mol / L. It can then be diluted with water to achieve a concentration of between 0.5 and 3 mol / L, for example, approximately 1.8 mol / L. This dilution also reduces the viscosity of the solution to values ​​close to that of pure water.

[0046] According to one feature of the invention, the alkaline potassium silicate solution may comprise a molar ratio (SiO2 / K2O) of silicon dioxide SiO2 to potassium oxide K2O of between 0.5 and 10, preferably between 1 and 5. For example, the alkaline potassium silicate solution may comprise a molar ratio of silicon dioxide SiO2 to potassium oxide K2O substantially equal to 4.

[0047] According to one embodiment of the invention, the aqueous gelling solution may comprise between 1 and 30% by mass of acetic acid, preferably between 10 and 20% by mass of acetic acid relative to the total mass of the aqueous gelling solution. Thus, it is possible to control the pH of the aqueous gelling solution. For example, the aqueous gelling solution may comprise approximately 16% by mass of acetic acid.

[0048] According to one aspect of the invention, the aqueous gelling solution may comprise between 0.1 and 1% by mass of aluminate, preferably approximately 0.5% relative to the total mass of the aqueous gelling solution. These ranges limit the syneresis mechanism within the gel without reaching a solubility limit for aluminate in water.

[0049] According to one embodiment of the invention, the aqueous silicate solution can be prepared by a 50 / 50 dilution of water and silicate. Thus, for this embodiment, the concentration of silicon (Si) can range from 0.25 to 3.5 mol / L, preferably from 0.25 to 1.5 mol / L, within the gelling aqueous solution.

[0050] According to a non-limiting example, the aqueous gelling solution can be prepared from:

[0051] 12.3% by mass of acetic acid at 2 mol / L

[0052] - 43.6% by mass of potassium silicate solution,

[0053] - 0.5% by mass of sodium aluminate,

[0054] - 43.6% by mass of water.

[0055] In this example, this aqueous gelling solution comprises:

[0056] - 85.5% by mass of water (of the aqueous gelling solution),

[0057] - 8.9% silica by mass,

[0058] - 3.6% potassium by mass,

[0059] 1.5% by mass of acetic acid, and

[0060] - 0.5% by mass of sodium aluminate.

[0061] This preferred embodiment allows for a compromise between gelation time, viscosity, and limiting the syneresis mechanism, with the composition adjusted according to the parameters of the underground formation (notably a temperature of 15°C, etc.). However, the aqueous gelling solution, which must be adapted to the underground formation, may have other compositions.

[0062] When useful, and particularly when the temperature of the target formation is high, the gelation time can be further increased by using another weak acid, such as boric acid. The aqueous gelling solution may include any other compound that allows for its adaptation to underground formations.

[0063] To seal a porous formation around a well, the following procedure can be used:

[0064] - A gelling aqueous solution is prepared on the surface from an alkaline solution of potassium silicate, water, acetic acid, and an aluminate. Preferably, these mixtures are prepared gradually to avoid localized precipitation due to excessive concentration. Such gradual mixing devices are readily available, for example, for preparing gels from polymers. At surface temperatures lower than the expected temperature in the underground formation (e.g., 20°C compared to 40°C), the gelation kinetics are significantly slowed, thus increasing the time available for mixing. Preferably, the preparation can be carried out as follows: the aluminate is mixed with water, the potassium silicate is diluted with this water, and then the acetic acid is added, taking the temperature into account.For example, at a temperature of 15°C, 2M acetic acid can be used, and at a temperature of 40°C, 1M acetic acid can be used. The gelling mixture (the aqueous gelling solution) is injected into the formation, typically using conventional pumping methods. Upstream of the injected volume (the fluid contained in the well), water can be used without causing precipitation. Downstream of the injected volume, water can be used in the same way.

[0065] The order of magnitude for the gelling time of the aqueous gelling solution at 40°C is approximately 500 minutes, or 8.5 hours. This order of magnitude is sufficient to allow the aqueous gelling solution to be placed in the porous structure before gelling. For example, for a porous volume of approximately 10 m³ 3 within a 1 m radius around a well and to a height of 10 m with a porosity of 30% - using a typical pumping flow rate of 10 m 3The injection time for the aqueous gelling solution is 1 hour. To this must be added the time it takes for the solution to travel through the well, which can last approximately 3 hours depending on the technique used and the diameter of the injection tube. For example, a few liters of the aqueous gelling solution can be used to cement a well.

[0066] To wash the underground formation, the process may include a step of injecting a buffer fluid, such as fresh water, prior to injecting the aqueous gelling solution. Furthermore, the washing fluid may contain viscosifying additives to improve washing.

[0067] In the case of an acid gas storage well, the volume of injected scrubbing fluid is preferably sufficient to push the acid gas to a radial distance of at least a few meters from the wellhead. This rinsing, preferably with water, subsequently ensures good injectivity of the aqueous gelling solution containing the reactive material around the wellhead. Without rinsing, the method could be less effective because there is a risk of rapid formation of surface mineral compounds (carbonates and / or sulfides) that could locally clog the pores, thus limiting the penetration of the reactive formulation into the wellhead.

[0068] The process may also include a well-sealing step after injection of the gelling aqueous solution.

[0069] For example, the operation may conclude with the injection of a cement plug, or other sealing compound, to hold the reactive material in place. Once this initial step is complete, the same procedure can be repeated in other areas, particularly on the tank roof, after perforating the lining and primary cement to allow for injection.

[0070] The process according to the invention can be applied to an acid gas storage well in an underground formation. It can also be applied to a production or exploration well in an underground formation containing hydrocarbons. It can also be applied to a well used for hydrocarbon recovery by fracturing, particularly hydraulic fracturing. In this case, the aqueous gelling solution seals the perforation and / or fractures created by the process. Alternatively,

[0071] It can be applied to any type of storage in an underground formation, for example, for the storage of radioactive materials. For all applications, the process according to the invention makes it possible, in particular, to limit gas leaks through the well, thanks to the sealing and / or consolidation of the underground formation.

[0072] The invention can also be applied to the closure of an injection well that has been decided to be decommissioned, which can be likened to the abandonment of an oil well. However, the invention can also be implemented during the construction of a well specifically drilled for the geological storage of acid gases, whether in reservoir rocks, aquifers, or coal seams.

[0073] The invention also applies to the consolidation of clay soils on which houses, or any type of building, are constructed, and to the consolidation of sandy soils with low mechanical resistance. For this application, the method according to the invention is particularly advantageous for houses and buildings where the behavior of the clay soil has caused damage. In this context, the method may comprise the following steps:

[0074] - at least one well or injector is dug beneath the dwelling or building, for example at a depth of a few meters below the dwelling or building,

[0075] - A gelling aqueous solution is prepared on the surface from an alkaline solution of potassium silicate, water, acetic acid, and an aluminate. Preferably, these mixtures are prepared gradually to avoid localized precipitation due to excessive concentration. Such gradual mixing devices are readily available, for example, for preparing gels from polymers. At surface temperatures lower than the expected temperature in the underground formation (e.g., 20°C compared to 40°C), the gelation kinetics are significantly slowed, thus increasing the time available for mixing. Preferably, the preparation can be carried out as follows: the aluminate is mixed with water, the potassium silicate is diluted with this water, and then the acetic acid is added, taking the temperature into account.For example, for a temperature of 15°C, we can use 2M acetic acid, and for a temperature of 40°C, we can use 1M acetic acid.

[0076] - The gelling mixture (the aqueous gelling solution) is injected into the well or injector, typically using conventional pumping methods; upstream of the injected volume (the fluid contained in the well), water can be used without causing precipitation. Downstream of the injected volume, water can also be used in the same way.

[0077] Example

[0078] The characteristics and advantages of the process according to the invention will become clearer upon reading the comparative example below.

[0079] For this example, we compare the syneresis mechanism implemented for a gel formed by the prior art process described in patent application FR 3049642 (WO 2017 / 174243), i.e. without aluminate, to the syneresis mechanism for a gel formed by the process according to the invention, i.e. with aluminate.

[0080] The aqueous gelling solution of the prior art process is prepared at room temperature with an alkali silicate (Betol K 28 T), fresh water, and 2 mol / L acetic acid.

[0081] The aqueous gelling solution of the process according to the invention is prepared with the addition of sodium aluminate. It can be noted that, with the quantities used, the amount of silicon substituted by aluminum is at most 10% in the gel thus formed. The aqueous gelling solution thus formed comprises 43.6% by mass of water, 43.6% by mass of silicate, 12.3% of acetic acid, and 0.5% by mass of sodium aluminate.

[0082] For this comparative example, the two gels are generated in test tubes. Indeed, in a test tube, it is possible to distinguish between water inside and outside the gel (supernatant), thus allowing the kinetics of the mechanism to be evaluated. This measurement of water is implemented using magnetic resonance imaging by measuring the transverse relaxation times T2, which allows the water to be distinguished within and outside the gel.

[0083] The monitoring of water content in and out of the gel was carried out at a high temperature (60°C) in order to accelerate these transformations, which can take several weeks at lower temperatures. Figure 2 is a dimensionless graph of the water fraction in the gel, Fw (the value 1 representing the initial state during gel formation), as a function of time T in hours. In this figure, the AA curve corresponds to the gel formed by the prior art process, and the INV curve corresponds to the gel formed by the process according to the invention. Thus, this graph clearly shows the effect of adding sodium aluminate (INV) on the amount of water in the gel as a function of time. It should be noted that, in this example, the amount of aluminate added is practically at the limit of its solubility in water. Time t=0 corresponds to the formation of the gel at a low temperature (15°C). It is then heated to 60°C.At t=100 h, the amount of water in the gel for the process according to the invention is stabilized (being essentially constant between 100 and 900 h) and much greater than in the absence of aluminate according to the prior art (a water fraction in the gel of approximately 0.65 for the process according to the invention compared to a water fraction of approximately 0.3 for the process according to the prior art). Consequently, the process according to the invention limits the syneresis mechanism of the gel formed in the underground formation, which ensures good sealing and consolidation of the underground formation.

Claims

A method of treating a subterranean formation, said subterranean formation being traversed by at least one injection well, characterized in that the following steps are carried out:a) preparing a gelling aqueous solution comprising an alkaline solution of potassium silicate, acetic acid and an aluminate, andb) injecting from said injection well, into said subterranean formation, said gelling aqueous solution to seal or to consolidate said subterranean formation.The method as claimed in claim 1, wherein said aluminate is selected from among sodium aluminate in powder form and potassium aluminate in powder form. The method as claimed in claim 1, wherein said gelling aqueous solution is prepared based on characteristics of said subterranean formation. The method as claimed in claim 1, wherein a gelling aqueous solution with a viscosity of between 1 and 10 cP is prepared. The method as claimed in claim 1, wherein a gelling aqueous solution having a setting time of between 3 and 20 hours is prepared. The method as claimed in claim 1, wherein said acetic acid has a concentration of between 0.1 and 5 mol / L. The method as claimed in claim 1, wherein said alkaline solution of potassium silicate has a concentration of silicon Si of between 0.5 and 7 mol / L. The method as claimed in claim 1, wherein said alkaline solution of potassium silicate has a molar ratio of silicon dioxide SiO2 to potassium oxide K2O of between 0.5 and 10.The method as claimed in claim 1, wherein said gelling aqueous solution comprises between 1 and 30 mass % of acetic acidThe method as claimed in claim 1, wherein the gelling aqueous solution can comprise between 0.1 and 1 mass % of aluminate.The method as claimed in claim 1, wherein a washing fluid is injected from said injection well into said subterranean formation prior to injecting said gelling aqueous solution.The method as claimed in claim 1, wherein said subterranean formation treatment is sealing of said subterranean formation and / or consolidation of said subterranean formation or plugging of a well of said subterranean formation.The method as claimed in claim 1, wherein said well is a storage well.A method according to claim 13 wherein said well is storage wellfor storing acid gas in said subterranean formation.The method as claimed in claim 14, wherein said acid gas is stored prior to the step of injecting said gelling aqueous solution.The method as claimed in claim 12, wherein said subterranean formation treatment is a consolidation of a clay soil on which a house or a building is constructed.The method as claimed in claim 1, wherein said subterranean formation has a surrounding pH value below 9.

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