Synergistic Blend of Fluorine and Mineral Acids for Removing Sediments and Stimulating Geothermal Wells

Abstract

The present disclosure relates to the treatment of formation rock or scale. The rock or scale may be located in a geothermal well. The rock or scale may be treated with a stimulation fluid. The stimulation fluid includes a salt of a nitrogen base having a fluoroinorganic anion and an acid component. The rock may include quartz. The acid component may include hydrochloric acid.

Description

[Technical field]

[0001] The present disclosure relates generally to methods and fluids for treating formation rock and / or scale associated with geothermal systems. [Background technology]

[0002] Geothermal energy is energy in the form of heat inside the Earth, which is harvested by geothermal wells. The Earth's interior contains a huge potential energy supply due to its extremely high temperatures. However, there are many technical and economic challenges in optimizing the harvesting of this energy source. Nevertheless, the use of geothermal energy as a renewable energy source is gaining importance as other energy sources are becoming scarcer and more expensive.

[0003] Geothermal energy travels towards the surface by thermal conduction through rock. Thermal energy may also be transferred towards the surface by the movement of lava or the circulation of fluids (H2O as steam or water) through interconnected fractures and pores. This may provide a thermal reservoir closer to the surface and therefore more available locations for drilling wells to extract geothermal energy.

[0004] Natural geothermal reservoirs, in which many commercial geothermal wells are located, contain volumes of rock with high temperatures (up to about 350°C or more, depending on the depth of the well and the geographic location of the resource), high porosity and high permeability to fluids. A well is drilled into such a reservoir, and the thermal energy in the rock is transferred by conduction to a fluid (H2O as water or steam) that subsequently flows into the well and then to the surface. Summary of the Invention [Problem to be solved by the invention]

[0005] Geothermal power plants remain attractive from an environmental standpoint, but well sizing and associated equipment remain issues that must be addressed. In addition to generating electricity from these sources, the resources may also be used for process and district heating. Additionally, geothermal wells may need to be stimulated to improve the porosity of the formations and increase the productivity of the resource. [Means for solving the problem]

[0006] The present disclosure provides methods and fluids for treating formation rock and / or scale associated with geothermal systems. In some embodiments, a method of treating formation rock includes introducing a stimulation fluid into a wellbore of a well, the well including formation rock, and contacting the formation rock with the stimulation fluid, the stimulation fluid including a salt of a nitrogen base having a fluoro inorganic anion and an acid component.

[0007] The well may be a geothermal well and the fluoro-inorganic anion may be selected from the group consisting of tetrafluoroborate, hexafluorophosphate, and any combination thereof.

[0008] The nitrogen base may be selected from the group consisting of urea, biuret, alkylurea, alkanolamine, alkylamine, dialkylamine, trialkylamine, alkyldiamine, alkyltriamine, alkyltetramine, polyamine, acrylamide, polyacrylamide, vinylpyrrolidone, polyvinylpyrrolidone, and any combination thereof. In some embodiments, the nitrogen base comprises urea. In some embodiments, the salt of the nitrogen base with a fluoro inorganic anion is urea tetrafluoroborate.

[0009] In some embodiments, the acid component is selected from the group consisting of hydrochloric acid, hydrobromic acid, hydrofluoric acid, formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, methylsulfonic acid, and any combination thereof. In some embodiments, the acid component is hydrochloric acid. In some embodiments, the acid component does not include hydrofluoric acid.

[0010] The stimulation fluid may include from about 1% to about 50% by weight of a salt of a nitrogen base having a fluoro inorganic anion, and from about 1% to about 50% by weight of an acid component.

[0011] According to the method, treating the formation rock may include dissolving at least a portion of the formation rock with a stimulation fluid. In some embodiments, the formation rock includes a member selected from the group consisting of quartz, calcite, silica, silicates, aluminosilicates, calcium, magnesium, iron, iron oxide, iron sulfide, lead, arsenic, antimony, and any combination thereof. In some embodiments, the formation rock includes quartz.

[0012] The stimulation fluid may include an aqueous carrier fluid and a corrosion inhibitor. The stimulation fluid may be introduced into the well using a chemical injection pump, drip techniques, spray techniques, immersion techniques, or any combination thereof.

[0013] The present disclosure also provides a method of treating a formation rock comprising contacting the formation rock with a stimulation fluid, the stimulation fluid comprising a salt of a nitrogen base having a fluoro inorganic anion, and an acid component.

[0014] The fluoro inorganic anion may be selected from the group consisting of tetrafluoroborate, hexafluorophosphate, and any combination thereof.

[0015] The nitrogen base may be selected from the group consisting of urea, biuret, alkylurea, alkanolamine, alkylamine, dialkylamine, trialkylamine, alkyldiamine, alkyltriamine, alkyltetramine, polyamine, acrylamide, polyacrylamide, vinylpyrrolidone, polyvinylpyrrolidone, and any combination thereof.

[0016] The acid component may be selected from the group consisting of hydrochloric acid, hydrobromic acid, hydrofluoric acid, formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, methylsulfonic acid, and any combination thereof.

[0017] The formation rock may include a member selected from the group consisting of quartz, calcite, silica, silicate, aluminosilicate, calcium, magnesium, iron, iron oxide, iron sulfide, lead, arsenic, antimony, and any combination thereof.

[0018] The present disclosure also provides a method of treating scale comprising contacting the scale with a stimulation fluid, the stimulation fluid comprising a salt of a nitrogen base having a fluoro inorganic anion and an acid component. The method may also include introducing the stimulation fluid into a wellbore of a well, the well comprising the scale, and contacting the scale with the stimulation fluid.

[0019] In some embodiments, the scale is located on a member selected from the group consisting of a pipeline, a heat exchanger, an evaporator, a rock formation, a heating unit, and any combination thereof.

[0020] The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the present disclosure that form the subject matter of the claims of this application will be described below. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present disclosure. It should also be recognized by those skilled in the art that such equivalent embodiments do not depart from the spirit and scope of the present disclosure as set forth in the appended claims. [Brief description of the drawings]

[0021] A detailed description of the invention is set forth herein below with specific reference to the following drawings:

[0022] [Figure 1] 1 is a graph showing results from various dissolution tests using different fluids. [Diagram 2] 1 is a graph showing results from various dissolution tests using different fluids. [Diagram 3] 1 is a graph showing results from various dissolution tests using different fluids. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present disclosure provides stimulation fluids, methods of treating rocks using stimulation fluids, methods of treating wells, such as geothermal wells, and methods of treating scales using stimulation fluids. According to the present disclosure, with respect to scales, "treatment" may include prevention, dissolution, removal, reduction, any combination of the above, and any other effect that may occur by contacting scales with the stimulation fluids of the present disclosure. With respect to rocks, "treatment" may include dissolution, removal, reduction, any combination of the above, and any other effect that may occur by contacting rocks with the stimulation fluids of the present disclosure. Furthermore, the terms "rocks," "formation rocks," "reservoir rocks," and the like, are used interchangeably and are intended to include all solid mineral materials, such as quartz, and any other rocks found, for example, in geothermal wells. In some embodiments, "stimulation" refers to a process used to increase the flow of brine from a geothermal well.

[0024] The stimulation fluid disclosed herein may include various components. For example, the stimulation fluid may include an aqueous carrier fluid as a continuous phase. The aqueous carrier fluid may be selected from, but is not limited to, fresh water, acid water, salt water, sea water, produced water, or any combination thereof. In some embodiments, the stimulation fluid may also include one or more organic solvents.

[0025] The stimulation fluid disclosed herein also includes a salt of a nitrogen base having a fluoro inorganic anion, and an acid component. In some embodiments, the fluoro inorganic anion is selected from the group consisting of tetrafluoroborate, hexafluorophosphate, and any combination thereof. In some embodiments, the fluoro inorganic anion includes tetrafluoroborate. Moreover, the stimulation fluid may include hydrolysis products of tetrafluoroborate and / or hexafluorophosphate that contain fluorine atoms.

[0026] A nitrogen base (e.g., urea) can react with a fluoroinorganic acid (e.g., fluoroboric acid) to form a salt of the nitrogen base with a fluoroinorganic anion (e.g., urea tetrafluoroborate). In some embodiments, the nitrogen base is selected from the group consisting of urea, biuret, alkylurea, alkanolamine, alkylamine, dialkylamine, trialkylamine, alkyldiamine, alkyltriamine, alkyltetramine, polyamine, acrylamide, polyacrylamide, vinylpyrrolidone, polyvinylpyrrolidone, and any combination thereof. In some embodiments, the nitrogen base comprises urea.

[0027] Unless otherwise indicated, the "alkyl" groups described herein, alone or as part of another group, are optionally substituted straight-chain saturated monovalent hydrocarbon groups or optionally substituted branched saturated monovalent hydrocarbon groups. Straight-chain or branched-chain alkyl groups can have from 1 to 32 carbon atoms. Examples of unsubstituted alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, i-pentyl, s-pentyl, t-pentyl, and the like.

[0028] In some embodiments, tetrafluoroboric acid, commonly referred to as fluoroboric acid (HBF4), is combined with a nitrogen base to form the corresponding tetrafluoroborate salt. Consistent with the broader aspects of the present disclosure, one or more substantially equivalent bases in terms of basic strength, or compounds that impart basic functionality, can be used in place of or in combination with urea.

[0029] In some embodiments, the stimulation fluid can include a molar ratio of the nitrogen base (such as urea) and the fluoro-inorganic acid (such as tetrafluoroboric acid) used to prepare the salt, for example, from about 1:3 to about 5:1, from about 1:3 to about 3:1, or from about 1:2 to about 3:1. The nitrogen base, e.g., the urea component, can react with an inorganic acid, such as tetrafluoroboric acid, to form a salt of the nitrogen base, such as urea tetrafluoroborate.

[0030] The concentration of the salt of the nitrogen base (such as urea) and the inorganic acid (tetrafluoroboric acid) in the stimulation fluid may be, for example, about 1% by weight to about 50% by weight, about 1% by weight to about 30% by weight, about 1% by weight to about 15% by weight, about 5% by weight to about 50% by weight, about 5% by weight to about 30% by weight, about 5% by weight to about 15% by weight, about 5% by weight to about 90% by weight, about 10% by weight to about 80% by weight, about 50% by weight to about 70% by weight, about 50% by weight to about 60% by weight, about 60% by weight to about 90% by weight, about 60% by weight to about 80% by weight, about 60% by weight to about 70% by weight, about 70% by weight to about 90% by weight, about 80% by weight to about 90% by weight, or about 70% by weight to about 80% by weight.

[0031] The stimulation fluid disclosed herein also includes an acid component. In some embodiments, the acid component may be selected from the group consisting of hydrochloric acid, hydrobromic acid, hydrofluoric acid, formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, methylsulfonic acid, and any combination thereof. However, the acid component is not limited to the above. In addition, the stimulation fluid of the present disclosure may not include any of the above acids, such as hydrofluoric acid. In general, any component explicitly disclosed herein may or may not be included in the stimulation fluid.

[0032] In some embodiments, the stimulation fluid comprises about 1% to about 50% by weight of a salt of a nitrogen base having a fluoro inorganic anion, and about 1% to about 50% by weight of an acid component. For example, the stimulation fluid may comprise about 15% by weight of an acid component and about 30% by weight of a salt of a nitrogen base having a fluoro inorganic anion, or the stimulation fluid may comprise about 5% to about 15% by weight of an acid component and about 5% to about 15% by weight of a salt of a nitrogen base having a fluoro inorganic anion. As an additional example, the stimulation fluid may comprise about 5% by weight of an acid component and about 5% by weight of a salt of a nitrogen base having a fluoro inorganic anion. The remainder of the stimulation fluid may comprise, for example, an aqueous carrier fluid, a solvent, additional additives, and the like.

[0033] In addition to the above components, the stimulation fluid of the present disclosure may include one or more additional additives. The additives include, but are not limited to, surfactants, gel stabilizers, antioxidants, permeability modifiers, scale inhibitors, corrosion inhibitors, foaming agents, defoaming agents, antifoaming agents, emulsifiers, demulsifiers, iron adjusters, proppants or other particulates, particulate diverters, salts, acids, fluid loss control additives, gases, catalysts, clay adjusters, dispersants, flocculants, scavengers (e.g., H2S scavengers, CO2 scavengers, or O2 scavengers), gelling agents, lubricants, friction reducers, crosslinkers, thickeners, weighting agents, solubilizers, pH adjusters (e.g., buffers), hydrate inhibitors, caking agents, bactericides, catalysts, clay stabilizers, breakers, delayed release breakers, and the like. Combinations of any of these additives may also be used.

[0034] The above salts of urea and tetrafluoroboric acid are disclosed in US Pat. Nos. 8,389,453 and 8,796,195, the contents of which are incorporated herein by reference in their entireties.

[0035] The relative amounts and / or concentrations of the various components / additives in a stimulation fluid can vary widely depending on the desired function of the fluid, the amount of rock being treated, the level of scale being treated, etc.

[0036] As previously mentioned, the rocks disclosed herein may include many different minerals. In some embodiments, the rocks include one or more components selected from the group consisting of quartz, calcite, silica, silicates, aluminosilicates, calcium, magnesium, iron, iron oxide, iron sulfide, lead, arsenic, antimony, amorphous silica, and any combination thereof. In some embodiments, the rocks include quartz, calcite, amorphous silica, and any combination thereof. In some embodiments, the rocks include quartz and / or calcite.

[0037] According to the present disclosure, the term "scale" is used to refer to a deposit / coating that includes mineral solids and / or sediment. The deposit / coating may form on a variety of surfaces, such as rock surfaces, or on the surface of a piece of equipment, such as a heat exchanger or pipeline. In some embodiments, the scale comprises a member selected from the group consisting of calcium salts, magnesium salts, silica, stibnite (antimony sulfide), and any combination thereof.

[0038] The stimulation fluids disclosed herein may be used to treat rocks, where the treatment may include dissolving some or all of the rock. In some embodiments, the rocks are present in wells, such as, but not limited to, geothermal wells, oil wells, gas wells, injection wells, and / or production wells. The stimulation fluid is injected downhole to contact and treat the rock. By treating the rock, the stimulation fluid may dissolve the rock or portions of the rock to form veins, pores, etc., for example, to enhance the flow of geothermal fluids or oil. The stimulation fluid may be injected into the wellbore of the well using a chemical injection pump. Other methods known in the art may be used to introduce the stimulation fluid into the well. Such other methods include, for example, the use of various pressure devices, dripping, spraying, and / or immersion, including both online or offline. The stimulation fluids of the present disclosure may be used to treat rocks found in wells / subterranean formations, or may be used to treat rocks removed from the earth's surface, such as rocks located in a process plant.

[0039] In some embodiments, the scale is present at a location or piece of equipment in contact with the geothermal fluid. For example, the scale may be present in a wellbore at the rock surface, in a pipeline, or on a turbine. The method may include, for example, contacting scale deposits on the turbine with a stimulating fluid disclosed herein, or contacting scale deposits in a pipeline with a stimulating fluid disclosed herein. Additionally or alternatively, the stimulating fluid disclosed herein may be added to the geothermal fluid to prevent scale deposits from forming.

[0040] Certain aspects of the disclosure relate to a method of treating rock. The method includes introducing a stimulation fluid into a wellbore of a well containing rock and contacting the rock with the stimulation fluid to treat the rock. The stimulation fluid includes a salt of a nitrogen base having a fluoro-inorganic anion and an acid component. The well can be a geothermal well. The salt of a nitrogen base having a fluoro-inorganic anion can be urea tetrafluoroborate. The acid component can be free of hydrofluoric acid. The stimulation fluid can include an aqueous carrier fluid and a corrosion inhibitor. The stimulation fluid can be used to dissolve the rock, thereby opening more fractures, veins, and pores within the rock, thereby creating additional space and lowering resistance to the flow of brine.

[0041] Certain aspects of the present disclosure relate to a method of treating scale. The method includes introducing a stimulation fluid into a wellbore of a well containing scale and contacting the scale with the stimulation fluid to thereby treat the scale. The stimulation fluid includes a salt of a nitrogen base having a fluoro inorganic anion and an acid component. The well may be a geothermal well. The salt of a nitrogen base having a fluoro inorganic anion may be urea tetrafluoroborate. The acid component may be free of hydrofluoric acid. The stimulation fluid may include an aqueous carrier fluid and a corrosion inhibitor.

[0042] The corrosion inhibitor that can be used according to the present disclosure is not particularly limited. In some embodiments, the corrosion inhibitor is an imidazoline, a quaternary amine, a fatty acid, a phosphate ester, a carboxylic acid, an amine, a phosphate, a polyphosphate, a heavy metal, or a combination thereof.

[0043] In some embodiments, the corrosion inhibitor may be selected from quaternary salts of alkyl, hydroxyalkyl, alkylaryl, arylalkyl, or arylamines; monocyclic or polycyclic aromatic amine salts; imidazoline derivatives; mono-, di-, or trialkyl, or alkylaryl phosphate esters; hydroxylamine phosphate esters; polyol phosphate esters; and monomeric or oligomeric fatty acids.

[0044] One of ordinary skill in the art may select an appropriate amount of corrosion inhibitor to include in the stimulation fluid. In some embodiments, the stimulation fluid may include about 0 to about 10 wt. % of the corrosion inhibitor, such as about 0 to about 5 wt. %, about 0 to about 3 wt. %, or about 0 to about 1 wt. %. In some embodiments, the stimulation fluid includes about 0.1 to about 5 wt. % of the corrosion inhibitor, such as about 0.1 to about 3 wt. %, about 0.1 to about 1 wt. %, or about 0.1 to about 0.5 wt. %.

[0045] Over time, wells, such as geothermal wells, can lose productivity. The loss of productivity can be due to physical changes in the reservoir and / or the buildup of scale minerals that plug veins, fractures, and pores in the rock, thereby reducing the void space through which the brine can flow. The stimulation fluid of the present disclosure treats the scale, and once the scale is treated, the stimulation fluid can also treat any underlying rock.

[0046] The present disclosure also provides a method of treating rock comprising contacting the rock with a stimulation fluid, the stimulation fluid comprising a salt of a nitrogen base having a fluoro inorganic anion and an acid component. The rock does not have to be located in a well. The rock can be located, for example, in a process plant.

[0047] Moreover, the present disclosure provides a method of treating scale comprising contacting the scale with a stimulation fluid, the stimulation fluid comprising a salt of a nitrogen base having a fluoro inorganic anion and an acid component. The scale does not have to be located within the well. The scale can be located on a portion of equipment used in connection with a geothermal process, such as, for example, equipment used within the geothermal well or equipment used outside the geothermal well, such as pipelines, turbines, heat exchangers, evaporators, heating units, and any combination thereof. EXAMPLES

[0048] Working Example

[0049] Drill cuttings were obtained and analyzed by X-ray fluorescence and diffraction. The composition of the cuttings can be seen in Table 1.

[0050] [Table 1]

[0051] The cuttings were dried at about 105°C for about 24 hours. A known amount of cuttings was added to a sample bottle and the weight of the bottle was recorded. A known amount of fluid was then added to the bottle and the weight of the bottle was again recorded. The bottle was then placed in a shaking bath. Tests used various water temperatures in the bath ranging from about 40°C to about 90°C. Shaking was performed at about 100 rpm to about 500 rpm. The bottles were left in the bath for about 4 hours to about 168 hours. At the end of each test, the bottles were removed from the bath and about 5 mL of fluid was withdrawn from the bottle, filtered and submitted for ion chromatography analysis of a 1% solution (cation). Table 2 shows the filtrate analysis results.

[0052] [Table 2]

[0053] If all of the cuttings were dissolved, a calculation of the maximum concentration was made for any cation. This concentration was compared to the analyzed concentration. The remainder of the solution and cuttings were filtered. The remaining cuttings were weighed to assess the weight percent of dissolution.

[0054] The samples tested in Figures 1-3 had the following properties shown in Table 3.

[0055] [Table 3]

[0056] As can be seen in Figures 1-3, different fluids were tested as well as different elements (Ca, SiO2, Mg, Al, and Fe). Each element in the figures contains five columns as described above. The first column for each element in all drawing figures is water and the value is shown as 0 on the x-axis (meaning no dissolution occurred). The second column is a 4 wt% solution of GEO991, a tetrafluoroborate neutralized with urea. The third column is a 16 wt% solution of GEO991, and the fourth column is a 16 wt% HCl solution. The fifth column is a fluid containing about 4 wt% GEO991 and about 12 wt% HCl.

[0057] The results shown in Figures 1-3 indicate that certain components of the stimulation fluids disclosed herein exhibit synergistic effects. For example, a salt of a nitrogen base with a fluoro inorganic anion (such as urea tetrafluoroborate) and an acid component (such as hydrochloric acid) exhibit synergistic effects when used to dissolve rock and / or scale. For example, with respect to Figure 2, when a 16% HCl solution was used to treat the SiO2, 0% dissolution occurred. When a 4% solution of urea tetrafluoroborate was used to treat the SiO2, approximately 25% dissolution occurred. However, when a fluid containing approximately 4 wt% urea tetrafluoroborate and approximately 12 wt% HCl was used, approximately 56% dissolution occurred, which is unexpected since HCl had no effect on dissolution when used alone.

[0058] The components of the stimulation fluid disclosed herein act synergistically to treat scale and / or rock and enlarge openings, pores, veins, etc. found within the rock, thereby increasing geothermal productivity (including increased production flows and / or increased reinjection flows).

[0059] Advantageously, the stimulation fluid of the present disclosure does not emit gases during operation, as opposed to other processes, such as those involving the use of hydrofluoric acid, which generates harmful vapors. The stimulation fluid of the present disclosure is also much less corrosive than hydrofluoric acid.

[0060] Any fluid disclosed herein may comprise, consist of, or consist essentially of any of the components / additives disclosed herein. In accordance with the present disclosure, phrases such as "consist essentially of," "consists essentially of," "consisting essentially of," and the like limit the scope of the claims to particular materials or steps, and to materials or steps that do not materially affect the basic and novel characteristics of the claimed invention.

[0061] As used herein, the term "about" refers to a cited value that is within error resulting from the standard deviation found in their respective testing measurements, and where such error cannot be determined, "about" refers to within 10% of the cited value.

[0062] All of the fluids and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. The invention may be embodied in many different forms, and certain preferred embodiments of the invention are described in detail herein. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.

[0063] Additionally, unless expressly stated to the contrary, use of the term "a" is intended to include "at least one" or "one or more." For example, "a corrosion inhibitor" is intended to include "at least one corrosion inhibitor" or "one or more corrosion inhibitors."

[0064] Any ranges given in either absolute or approximate terms are intended to be inclusive of both, and any definitions used herein are intended to be illustrative, not limiting. Although the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein should be understood to encompass any subranges (including all fractional and whole values) subsumed therein.

[0065] Moreover, the present invention encompasses all possible combinations of any or all of the various embodiments described herein. It should also be understood that various changes and modifications to the preferred embodiments of the present invention described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. Accordingly, such changes and modifications are intended to be covered by the appended claims. Examples of embodiments of the present disclosure are listed in the following items [1] to

[23] . [1] 1. A method for treating formation rock, comprising: introducing a stimulation fluid into a wellbore of a well, the well including the formation rock; contacting the formation rock with the stimulation fluid, the stimulation fluid comprising a salt of a nitrogen base having a fluoro inorganic anion, and an acid component. [2] 2. The method of claim 1, wherein the well is a geothermal well. [3] 2. The method of claim 1, wherein the fluoro inorganic anion is selected from the group consisting of tetrafluoroborate, hexafluorophosphate, and any combination thereof. [4] 2. The method of claim 1, wherein the nitrogen base is selected from the group consisting of urea, biuret, alkyl urea, alkanolamine, alkyl amine, dialkyl amine, trialkyl amine, alkyl diamine, alkyl triamine, alkyl tetramine, polyamine, acrylamide, polyacrylamide, vinyl pyrrolidone, polyvinyl pyrrolidone, and any combination thereof. [5] 2. The method of claim 1, wherein the nitrogen base comprises urea. [6] 2. The method of claim 1, wherein the salt of the nitrogen base with the fluoro inorganic anion is urea tetrafluoroborate. [7] 2. The method of claim 1, wherein the acid component is selected from the group consisting of hydrochloric acid, hydrobromic acid, hydrofluoric acid, formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, methylsulfonic acid, and any combination thereof. [8] 2. The method of claim 1, wherein the acid component is hydrochloric acid. [9] 2. The method of claim 1, wherein the acid component does not comprise hydrofluoric acid.

[10] 2. The method according to claim 1, wherein the stimulation fluid comprises about 1% by weight to about 50% by weight of the salt of the nitrogen base having the fluoro inorganic anion, and about 1% by weight to about 50% by weight of the acid component.

[11] 2. The method of claim 1, wherein treating the formation rock comprises dissolving at least a portion of the formation rock with the stimulating fluid.

[12] 2. The method of claim 1, wherein the formation rock comprises a member selected from the group consisting of quartz, calcite, silica, silicate, aluminosilicate, calcium, magnesium, iron, iron oxide, iron sulfide, lead, arsenic, antimony, and any combination thereof.

[13] 2. The method of claim 1, wherein the formation rock comprises quartz.

[14] 2. The method of claim 1, wherein the stimulating fluid comprises an aqueous carrier fluid and a corrosion inhibitor.

[15] 2. The method of claim 1, wherein the stimulation fluid is introduced into the well using a chemical injection pump, a drip technique, a spray technique, a submersion technique, or any combination thereof.

[16] 1. A method for treating formation rock, comprising: The method includes contacting the formation rock with a stimulation fluid, the stimulation fluid including a salt of a nitrogen base having a fluoro inorganic anion, and an acid component.

[17] Item 17. The method of item 16, wherein the fluoro inorganic anion is selected from the group consisting of tetrafluoroborate, hexafluorophosphate, and any combination thereof.

[18] 17. The method of claim 16, wherein the nitrogen base is selected from the group consisting of urea, biuret, alkyl urea, alkanolamine, alkyl amine, dialkyl amine, trialkyl amine, alkyl diamine, alkyl triamine, alkyl tetramine, polyamine, acrylamide, polyacrylamide, vinyl pyrrolidone, polyvinyl pyrrolidone, and any combination thereof.

[19] Item 17. The method of item 16, wherein the acid component is selected from the group consisting of hydrochloric acid, hydrobromic acid, hydrofluoric acid, formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, methylsulfonic acid, and any combination thereof.

[20] 17. The method of claim 16, wherein the formation rock comprises a member selected from the group consisting of quartz, calcite, silica, silicate, aluminosilicate, calcium, magnesium, iron, iron oxide, iron sulfide, lead, arsenic, antimony, and any combination thereof.

[21] A method for processing scale, comprising the steps of: The method includes contacting the scale with a stimulation fluid, the stimulation fluid including a salt of a nitrogen base having a fluoro inorganic anion, and an acid component.

[22] 22. The method of claim 21, further comprising the steps of: introducing the stimulation fluid into a wellbore of a well, the well containing the scale; and contacting the scale with the stimulation fluid.

[23] 22. The method of claim 21, wherein the scale is located on a member selected from the group consisting of a pipeline, a heat exchanger, an evaporator, a rock formation, a heating unit, and any combination thereof.

Claims

1. 1. A method for treating formation rock, comprising: introducing a stimulation fluid into a wellbore of a well, the well including the formation rock; contacting the formation rock with the stimulation fluid, the stimulation fluid including a salt of a nitrogen base having a fluoro inorganic anion and an acid component; dissolving at least a portion of the silica contained in the formation rock with the stimulation fluid; the nitrogen base is selected from the group consisting of urea, biuret, alkyl urea, alkanolamine, alkyl amine, dialkyl amine, trialkyl amine, alkyl diamine, alkyl triamine, alkyl tetramine, polyamine, acrylamide, polyacrylamide, vinyl pyrrolidone, polyvinyl pyrrolidone, and any combination thereof; the acid component is hydrochloric acid, The method, wherein the stimulation fluid comprises 1% to 15% by weight of the salt of the nitrogen base having the fluoro inorganic anion, and 1% to 15% by weight of the acid component.

2. The method of claim 1 , wherein the well is a geothermal well.

3. 2. The method of claim 1, wherein the fluoro inorganic anion is selected from the group consisting of tetrafluoroborate, hexafluorophosphate, and any combination thereof.

4. The method of claim 1 , wherein the nitrogen base comprises urea.

5. 2. The method of claim 1, wherein the salt of the nitrogen base with the fluoro inorganic anion is urea tetrafluoroborate.

6. 2. The method of claim 1, wherein the stimulation fluid comprises 1% to 5% by weight of the salt of the nitrogen base having the fluoro inorganic anion, and 5% to 15% by weight of the acid component.

7. 10. The method of claim 1, wherein the formation rock further comprises a member selected from the group consisting of quartz, calcite, silicate, aluminosilicate, calcium, magnesium, iron, iron oxide, iron sulfide, lead, arsenic, antimony, and any combination thereof.

8. The method of claim 1 , wherein the formation rock comprises quartz.

9. The method of claim 1 , wherein the stimulation fluid comprises an aqueous carrier fluid and a corrosion inhibitor.

10. 10. The method of claim 1, wherein the stimulation fluid is introduced into the well using a chemical injection pump, a drip technique, a spray technique, a submersion technique, or any combination thereof.

11. 1. A method for treating formation rock, comprising: contacting the formation rock with a stimulation fluid, the stimulation fluid including a salt of a nitrogen base having a fluoro inorganic anion and an acid component; dissolving at least a portion of the silica contained in the formation rock with the stimulation fluid; the nitrogen base is selected from the group consisting of urea, biuret, alkyl urea, alkanolamine, alkyl amine, dialkyl amine, trialkyl amine, alkyl diamine, alkyl triamine, alkyl tetramine, polyamine, acrylamide, polyacrylamide, vinyl pyrrolidone, polyvinyl pyrrolidone, and any combination thereof; the acid component is hydrochloric acid, The method, wherein the stimulation fluid comprises 1% to 15% by weight of the salt of the nitrogen base having the fluoro inorganic anion, and 1% to 15% by weight of the acid component.

12. 12. The method of claim 11, wherein the fluoro inorganic anion is selected from the group consisting of tetrafluoroborate, hexafluorophosphate, and any combination thereof.

13. 12. The method of claim 11, wherein the formation rock further comprises a member selected from the group consisting of quartz, calcite, silicate, aluminosilicate, calcium, magnesium, iron, iron oxide, iron sulfide, lead, arsenic, antimony, and any combination thereof.

14. A method for processing scale, comprising the steps of: contacting the scale with a stimulation fluid, the stimulation fluid including a salt of a nitrogen base having a fluoro inorganic anion and an acid component; Dissolving at least a portion of the silica contained in the scale with the stimulating fluid; the nitrogen base is selected from the group consisting of urea, biuret, alkyl urea, alkanolamine, alkyl amine, dialkyl amine, trialkyl amine, alkyl diamine, alkyl triamine, alkyl tetramine, polyamine, acrylamide, polyacrylamide, vinyl pyrrolidone, polyvinyl pyrrolidone, and any combination thereof; the acid component is hydrochloric acid, The method, wherein the stimulation fluid comprises 1% to 15% by weight of the salt of the nitrogen base having the fluoro inorganic anion, and 1% to 15% by weight of the acid component.

15. 15. The method of claim 14, further comprising the steps of: introducing the stimulation fluid into a wellbore of a well, the well containing the scale; and contacting the scale with the stimulation fluid.

16. 15. The method of claim 14, wherein the scale is located on a member selected from the group consisting of a pipeline, a heat exchanger, an evaporator, a rock formation, a heating unit, and any combination thereof.

17. the stimulation fluid comprises about 4% by weight of the salt of the nitrogen base having the fluoro inorganic anion and about 12% by weight of the acid component; 2. The method of claim 1, wherein the salt of the nitrogen base with the fluoro inorganic anion is urea tetrafluoroborate.

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