Aqueous fluid composition and method for removing barite scale using same

Abstract

Barite (barium sulfate) scale may be a problem in subterranean formations, wellbores, pipelines and other locations, and may be difficult to remove in many cases. An aqueous fluid composition effective to remove barite scale may include a concentrated mineral acid, a first salt including an iodide anion, and a second salt including an anion that forms a water-soluble barium salt. A suitable aqueous fluid composition may include concentrated hydriodic acid, an alkali metal iodide, and an alkali metal hypophosphite. The aqueous fluid composition may be used in combination with a second treatment stage comprising a fluid composition comprising at least one acid gas trapping agent. The at least one acid gas trapping agent may comprise a first component reactive to hydrogen sulfide and optionally a second component reactive to carbon dioxide.

Description

Technical Field

[0001] The present disclosure relates generally to scale dissolution and, more particularly, to aqueous fluid compositions effective for at least partially dissolving barite scale in specific locations, such as in subterranean formations and pipelines. Background Art

[0002] Barium sulfate (BaSO4), also commonly referred to as barite in its mineral form, is a commonly used weighting agent used to produce high-density drilling fluids to maintain hydrostatic pressure when drilling in subterranean formations. While effective for the above purposes, the presence of barite can become a problem once it is introduced into a wellbore. Residual barite can be difficult to remove from a wellbore due to its relatively low solubility in aqueous fluids (approximately 2.5 mg / L at 25°C), including aqueous acids commonly used downhole. In addition, when dissolving the barite to affect its removal, it is also easy to exceed the solubility limit, causing the barite to reprecipitate as barite scale. Reprecipitated barite scale can be even more difficult to remove due to its increased hardness and crystallinity compared to natural or synthetic barite, which is often the result of barite scale binding to formation water impurities (e.g., monovalent and divalent cations, minerals, and other dissolved solids). Barite scale formation can result in a number of serious consequences including, for example, formation damage, increased and potentially unplanned workovers of downhole equipment and formation areas, equipment or pipeline downtime, production losses, high costs to replace unrepairable equipment, and the like.

[0003] Baryte scale can be removed from the location where it occurs by chemical, mechanical and / or physical treatment methods. Mechanical and physical treatment methods involve removing barite scale from the surface and may be expensive, time-consuming and complex to operate. In some cases, the injection of aqueous fluids can also be used to help remove barite scale. Chemical methods for removing barite scale can utilize acids or chelating agents to promote the dissolution of barite scale. Excessive use of acid may be undesirable due to the cost of acid, waste disposal issues (especially for acid solutions that are not completely exhausted), and the potential corrosiveness of metal surfaces in downhole, near-well areas and pipelines. In addition, since the chemical form of barite remains unchanged after dissolution in acid, the reprecipitation of barite scale remains a significant risk even if the dissolution conditions are carefully controlled. Chelating agents can alleviate this difficulty to a certain extent, but chelating agents may be expensive, and effective chelation of barium ions may not easily occur under all conditions where barite scale forms. For example, in some cases, the local pH environment near barite scale or in a fluid that promotes the dissolution of barite scale may be ineffective for barium ion chelation to occur.

[0004] In some cases, it may not be feasible to avoid conditions that lead to barite scale formation. For example, it may not be possible to avoid exposure of dissolved barite to incompatible formation water, and / or it may not be possible to add sufficient aqueous fluid to keep the barite concentration below the solubility limit. In view of the foregoing, further strategies for removing barite and barite scale in various locations would be highly desirable. Summary of the invention

[0005] Various details of the present disclosure are summarized below to provide a basic understanding. The present disclosure is not a comprehensive review of the present disclosure, and is neither intended to identify certain elements of the present disclosure nor to limit the scope of the present disclosure. On the contrary, the main purpose of the present disclosure is to present some concepts of the present disclosure in a simplified form before the more detailed description presented below.

[0006] According to various embodiments consistent with the present disclosure, an aqueous fluid composition can include: a concentrated inorganic acid; a first salt including an iodide anion; and a second salt including an anion that forms a water-soluble barium salt.

[0007] In other embodiments consistent with the present disclosure, the scale dissolution system may include: a first treatment stage comprising an aqueous fluid composition, the aqueous fluid composition comprising: a concentrated inorganic acid; a first salt comprising an iodide anion; and a second salt comprising an anion that forms a water-soluble barium salt; and a second treatment stage, the second treatment stage comprising a fluid composition containing at least one acidic gas capture agent.

[0008] In other embodiments consistent with the present disclosure, a scale dissolution method may include: introducing an aqueous fluid composition into a location containing barite scale, the aqueous fluid composition comprising: a concentrated inorganic acid; a first salt comprising an iodide anion; and a second salt comprising an anion that forms a water-soluble barium salt; and contacting the barite scale with the aqueous fluid composition for a sufficient time to dissolve at least a portion of the barite scale.

[0009] Any combination of the various embodiments and implementations disclosed herein may be used in another embodiment consistent with the present disclosure.These and other aspects and features may be understood from the following description of certain embodiments presented herein, in light of the present disclosure and the accompanying drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a SEM image of synthetic industrial-grade barite.

[0011] Figure 2 This is a SEM image of barite scale underground.

[0012] Figure 3 is a graph of barite solubility as a function of immersion time under various conditions.

[0013] Figure 4 The solubility of synthetic industrial grade barite is compared with the solubility of downhole barite scale at 100°C and 130°C with an 8-hour soak time.

[0014] Figure 5 is a graph comparing the solubility of downhole barite scale alone at 130°C with the solubility measured under similar conditions in the presence of formation water or crude oil.

[0015] Figure 6 is a graph showing the progression of barite scale dissolution and subsequent generation and capture of acid gas at 130°C. DETAILED DESCRIPTION

[0016] The present disclosure relates generally to scale dissolution and, more particularly, to aqueous fluid compositions effective for at least partially dissolving barite scale in specific locations, such as in subterranean formations and pipelines.

[0017] As described above, barite scale can lead to many serious consequences in oil and gas production, including the potential closure of a work site or the need for expensive and time-consuming workover operations. Removal of barite scale can be very difficult, whether by mechanical, physical or chemical methods. Chemical methods to dissolve barite scale may be effective in some cases, but they may present a significant risk of reprecipitation of barite scale when solubility limits are exceeded and / or when exposed to incompatible formation waters. Reprecipitated barite scale may form unexpectedly and may form in locations that are even more difficult to remove. Therefore, removal of barite scale remains an ongoing problem in oil and gas production.

[0018] In response to the above needs, the present disclosure provides an aqueous fluid composition that can effectively dissolve barite or barite scale in various working environments, such as in underground formations, wellbores penetrating underground formations, factories or pipelines. In particular, the aqueous fluid composition disclosed herein can include a concentrated mineral acid, a first salt (iodide salt) containing an iodine anion, and a second salt containing an anion that forms a water-soluble barium salt. In a more specific example, the concentrated mineral acid can include concentrated hydroiodic acid, and the second salt can also be a reducing agent. Hypophosphite, such as sodium hypophosphite monohydrate (NaH2PO2·H2O), can be a particularly desirable second salt that is both a reducing agent and can provide anions for forming a water-soluble barium salt. Without being limited by theory or mechanism, it is believed that sodium hypophosphite monohydrate relaxes the topmost unit cell layer of the barite crystal, thereby causing the destruction of the bond distance between the oxygen atoms in the barium ion and the sulfate anion, and promoting dissolution, as further described below.

[0019] The use of hydroiodic acid in combination with an iodide salt and sodium hypophosphite monohydrate may provide many advantages for dissolving barite. At a minimum, these reagents may interact with each other in a complementary manner to promote barite dissolution. Without being limited by theory or mechanism, dissolution of barite using the aforementioned reagents is believed to occur via reactions 1 to 3. The net reaction is shown in reaction 4.

[0020] BaSO 4(s) +2NaH2PO 2(aq) →Na2SO 4(aq) +Ba(H2PO2) 2(aq) (Reaction 1)

[0021] Na2SO 4(aq) +2HI (aq) →H2SO 4(aq )+2NaI (aq) (Reaction 2)

[0022] H2SO 4(aq) +8HI (aq) →H2S (aq) +4I 2(aq) +4H2O (Reaction 3)

[0023] BaSO 4(aq) +2NaH2PO 2(aq) +10HI (aq) →Ba(H2PO2) 2(aq) +2NaI (aq) +4I 2(aq) +H2S (aq) +4H2O (Reaction 4)

[0025] Considering the above reactions, the dissolution of barite is driven by two complementary factors: 1) sulfate anions (SO4 2- ) and hypophosphite (H2PO2 - ) exchange to form a soluble barium salt, and 2) the resulting free sulfate anions are converted to hydrogen sulfide (H2S). The conversion of sulfate to hydrogen sulfide can significantly reduce the risk of converting water-soluble barium salts into insoluble barite scale. In addition, the amount of sodium hypophosphite monohydrate in the aqueous fluid composition can at least partially determine the amount of barium hypophosphite formed and potentially dissolved (if the solubility limit of the salt is not exceeded). Therefore, depending on the amount of barite that needs to be dissolved, the amount of sodium hypophosphite monohydrate in the aqueous fluid composition can be adjusted as needed to promote the desired solubility. That is, sodium hypophosphite monohydrate can be used as a limiting reagent in the barite scale dissolution process. If the sodium hypophosphite monohydrate salt is the limiting reagent (or if there is no second reducing agent), the NaI and I2 formed in the above reaction may further form triiodide ions (I3- ) as a subsequent reaction product. However, if an excess of sodium hypophosphite monohydrate remains (or if a second reducing agent is present), any triiodide ions formed may subsequently be reduced to iodide ions, which may continue to promote the reduction of sulfate according to the aforementioned reactions. It should be further understood that the phase equilibrium of various iodine-containing species between the liquid and gas phases may additionally affect any subsequent reactions that occur after the barite scale is dissolved (for clarity, the phase equilibrium is not shown in reactions 1 to 4). In addition, at reservoir temperatures above about 72°C, any triiodide ions that are hypothetically formed may be converted to hypoiodous acid (HIO), which is unstable and may subsequently disproportionate to iodate (IO3 - ) ions and iodine ions, further promoting the dissolution of barite scale.

[0026] In addition to the above characteristics, hydroiodic acid is an advantageous mineral acid for use in conjunction with dissolving barite because hydroiodic acid can provide a high concentration of iodide ions to facilitate the reduction of sulfate anions. The iodide ions provided by hydroiodic acid can be further supplemented with iodide ions provided by iodide salts. Therefore, hydroiodic acid can reduce the amount of iodide salts required to provide a sufficient amount of iodide anions to reduce sulfate anions.

[0027] Compared to other inorganic acids, hydroiodic acid is also advantageous in other respects. Although other inorganic acids, such as concentrated hydrochloric acid or concentrated hydrobromic acid, can also effectively promote the conversion of sulfate anions to hydrogen sulfide (if sufficient iodide anions are present and provided by an iodide salt), as shown in Reaction 2 and Reaction 3, other concentrated inorganic acids have much lower hydrogen halide concentrations than hydroiodic acid and therefore contain more water relative to the amount of dissolved hydrogen halide present. For example, the concentrations of concentrated hydrochloric acid and concentrated hydrobromic acid are about 36% and 48% w / v, respectively, while commercially available concentrated hydroiodic acid solutions can be as high as about 67% w / v. In accordance with the disclosure herein, limiting the amount of water present when dissolving barite can reduce the occurrence of side reactions that can reform sulfate anions from hydrogen sulfide, which can lead to the re-precipitation of barite scale if not carefully controlled.

[0028] In addition to promoting the formation of water-soluble barium salts, sodium hypophosphite monohydrate can also provide further advantages when used in combination with hydroiodic acid, particularly with respect to the reducing properties of the salt. Hydroiodic acid can partially degrade into elemental iodine and the unstable acid hydrogen triiodic acid. Elemental iodine can form triiodide anions when reacting with iodide anions provided by iodide salts, thereby reducing the total amount of iodide ions available for sulfate reduction. Sodium hypophosphite monohydrate can reduce triiodide anions or other oxidized iodine species back to iodide anions to promote the reductive dissolution of sulfate salts according to the present disclosure.

[0029] Even in conventional barite dissolution processes, acidic gases (e.g., carbon dioxide and hydrogen sulfide) are often formed or encountered downhole in the process of removing barite scale. For each unit amount of barite that reacts to form a water-soluble barium salt, the reaction chemistry described herein further produces an equimolar amount of hydrogen sulfide. Advantageously, acidic gases generated (or otherwise present in the downhole) in the process of dissolving barite according to the disclosure herein can be easily repaired by a second stage treatment with a fluid containing an acidic gas capture agent. The second stage treatment can be applied after the barite dissolution is complete or partially complete, or the second stage treatment can be added to an aqueous fluid composition that promotes the dissolution of barite. In either case, the release of acidic gases can be eliminated or significantly reduced. According to the above disclosure, the second stage treatment containing an acidic gas capture agent is not considered to significantly affect the reaction chemistry that promotes the dissolution of barite. As another advantage, by capturing hydrogen sulfide with an acidic gas capture agent, hydrogen sulfide reforms sulfate anions through a side reaction with water, thereby increasing the possibility of the risk of reprecipitating barite scale can be significantly reduced.

[0030] Because hydrogen sulfide is obtained as a result of the above-mentioned reaction chemistry, the second stage treatment disclosed herein can include at least one acidic gas capture agent reactive to hydrogen sulfide. Depending on whether carbonate minerals are present in the well, resulting in the production of carbon dioxide, at least one acidic gas capture agent reactive to carbon dioxide can be optionally present. Suitable acidic gas capture agents reactive to carbon dioxide can include various amines, such as aliphatic cyclic amines or acyclic amines. In some cases, amines can also be suitable for capturing hydrogen sulfide. Other suitable acidic gas capture agents reactive to hydrogen sulfide can include compounds that react with hydrogen sulfide through nucleophilic aromatic substitution. 4-bromotoluene (p-bromotoluene) is a representative example of aromatic compounds that can react with hydrogen sulfide to promote its interception in the aforementioned manner. 4-bromotoluene may be advantageous in this regard because it is relatively cheap, widely available and compatible with other components of the aqueous fluid composition disclosed herein. Other halogenated aromatic compounds, such as fluorinated aromatic compounds and halogenated heteroaromatic compounds, can also be suitable for capturing hydrogen sulfide. By contacting hydrogen sulfide with a halogenated aromatic compound under basic conditions, the hydrogen sulfide can be at least partially deprotonated, thereby increasing its nucleophilicity to react with the halogenated aromatic compound via nucleophilic aromatic substitution.

[0031] As used herein, the term "concentrated mineral acid" refers to an aqueous solution of a hydrogen halide, wherein the hydrogen halide is at or near saturation concentration in the aqueous solution. In a non-limiting example, the concentrated mineral acid used in the disclosure herein may include concentrated hydrochloric acid, concentrated hydrobromic acid, or concentrated hydroiodic acid. Concentrated hydroiodic acid may be particularly advantageous for the reasons discussed above. The concentration of concentrated hydroiodic acid may be from about 55% w / v to about 67% w / v, including about 57% w / v or about 67% w / v in a specific example.

[0032] In a non-limiting example, the first salt may include an alkali metal iodide. Alkali metal iodides suitable for use in the present disclosure may include lithium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, and any combination thereof. Sodium iodide and potassium iodide may be desirable because they are relatively low in cost relative to other alkali metal iodides.

[0033] In non-limiting examples, the second salt may include a hypophosphite, preferably an alkali metal hypophosphite or a hydrate thereof. Suitable alkali metal hypophosphites may include, for example, lithium hypophosphite, sodium hypophosphite, potassium hypophosphite, rubidium hypophosphite, cesium hypophosphite or any combination thereof. Sodium hypophosphite monohydrate may be desirable because such alkali metal hypophosphites are easily available. Hypophosphites may be particularly advantageous because they can simultaneously promote the formation of water-soluble barium salts and promote the reduction of sulfates.

[0034] In aqueous fluid compositions of the present disclosure, iodide ion can be provided by concentrated mineral acid (if concentrated hydroiodic acid is used), the first salt (iodide salt) or its arbitrary combination.If concentrated hydroiodic acid is used, hydroiodic acid can provide most of iodide ions on a molar basis.Optionally, if hydroiodic acid can provide enough iodide ions separately, the first salt can be omitted.Any ratio of hydroiodic acid and iodide salt can be used to provide iodide ion, and condition is that there are enough acids to provide enough hydrogen ions for the occurrence of reaction 2 and reaction 3.In non-limiting examples, the mol ratio of hydroiodic acid to the second salt (for example, hypophosphite) in aqueous fluid compositions can be about 5 or larger (in moles), and / or the mol ratio of total iodide ion to the second salt (for example, hypophosphite) in aqueous fluid compositions can be about 5 or larger.Total iodide ion in aqueous fluid compositions can be determined by the mole number of iodide ion in the hydroiodic acid (if present) of selected amount and the mole number of iodide ion in the first salt of selected amount. A molar ratio of 5 or more of total iodide ions relative to the second salt is the minimum stoichiometric ratio required to promote complete formation of a water-soluble barium salt according to reaction 1 and complete conversion of sulfate anions to hydrogen sulfide according to reactions 2 and 3. However, as described above, the actual reaction stoichiometric ratio may differ from the theoretical stoichiometric ratio due to phase equilibrium of various iodine-containing species. In order to provide a margin of error, the molar ratio of total iodide ions relative to the second salt may optionally be about 6 or more, or about 7 or more, or about 8 or more, or about 9 or more, or about 10 or more, for example, about 6 to about 10, or about 6 to about 8, or about 7 to about 10 relative to the second salt (e.g., hypophosphite). A molar ratio of less than 5 may also be effective, although in some cases the barite dissolution may be less complete. Any amount of the first salt and the second salt may be present in the concentrated mineral acid, up to the solubility limit in the concentrated mineral acid.

[0035] The amount of water in aqueous fluid composition as herein described can be limited as much as possible, to reduce the possibility of side reaction with hydrogen sulfide to reform sulfate anion. In non-limiting examples, except the trace moisture introduced from other sources, the water from concentrated mineral acid can be a unique water source in the aqueous fluid composition. In other non-limiting examples, other water can be added to the aqueous fluid composition with about 10 vol.% or less, or about 8 vol.% or less, or about 6 vol.% or less, or about 4 vol.% or less, or about 2 vol.% or less amount.

[0036] The aqueous fluid composition disclosed herein may comprise, consist of, or consist essentially of a concentrated mineral acid, a first salt comprising an iodide anion, and a second salt comprising an anion that forms a water-soluble barium salt. For example, the aqueous fluid composition may comprise, consist of, or consist essentially of concentrated hydroiodic acid, a first salt comprising an alkali metal iodide, and a second salt comprising an alkali metal iodide. It should be understood that additional components may be present in the aqueous fluid composition in response to specific conditions that may be present in a given location containing barite scale. Other components that may be optionally present (in the form of being dissolved in the aqueous fluid composition or suspended in the aqueous fluid composition) may include, but are not limited to, other salts, other acids (e.g., one or more organic acids), fluid loss control additives, gases, foaming agents, defoamers, corrosion inhibitors, scale inhibitors, catalysts, biocides, friction reducing polymers, iron control agents, bridging agents, dispersants, hydrogen sulfide scavengers, carbon dioxide scavengers, oxygen scavengers, lubricants, viscosity enhancers, crushers, weighting agents, inert solids, emulsifiers, emulsion diluents, emulsion thickeners, surfactants, circulation loss additives, pH control additives, buffers, cross-linking agents, stabilizers, chelating agents, mutual solvents, consolidating agents, complexing agents, particulate materials, and any combination thereof. If additional components are present, they may be selected so that they do not interfere with or react with the inorganic acid, the first salt, or the second salt.

[0037] As described above, removing barite scale with the aqueous fluid composition described herein can produce one or more acidic gases (e.g., hydrogen sulfide and carbon dioxide). When using the aqueous fluid composition, hydrogen sulfide may be produced due to chemical reactions to promote barite dissolution by sulfate reduction. In contrast, if the barite contains mixed carbonate minerals (e.g., limestone / calcium carbonate, dolomite, iron carbonate or other carbonate minerals) or the carbonate minerals are in contact with the aqueous fluid composition in the process of promoting the dissolution of barite scale, carbon dioxide may be produced.

[0038] Therefore, the present disclosure also provides a scale dissolution system, which can simultaneously or sequentially promote the dissolution of barite scale and capture the acidic gas produced together with the dissolution of barite scale. The scale dissolution system may include a first treatment stage and a second treatment stage, wherein the first treatment stage includes any of the above-mentioned aqueous fluid compositions, and the second treatment stage includes a fluid composition comprising at least one acidic gas capture agent. In various embodiments, at least one acidic gas capture agent in the second treatment stage may include at least a first component reactive to hydrogen sulfide. If carbon dioxide is encountered or expected to be produced, the at least one acidic gas capture agent in the second treatment stage may further include a second component reactive to carbon dioxide. That is, the second component that reacts with carbon dioxide may be optional in some cases.

[0039] The fluid composition limiting the second treatment stage can be aqueous or non-aqueous in nature. Although aqueous or non-aqueous fluid compositions can be used in the second treatment stage, the second treatment stage can be more desirably non-aqueous in nature, to limit the amount of water present, thereby reducing the possibility of the side reaction that may re-form sulfate anion, as discussed in more detail above with reference to the first treatment stage. In a non-limiting example, the second treatment stage can include a water-miscible organic solvent, such as methanol, ethanol, ethylene glycol, propylene glycol, glycol dimethyl ether, acetone, butanone, etc. The amount of the water-miscible organic solvent can make the at least one acidic gas capture agent remain dissolved once the second treatment stage has contacted the aqueous fluid composition associated with the first treatment stage. That is, the second treatment stage can promote the liquid-liquid interception of at least one acidic gas.

[0040] Suitable acid gas capture agents for sequestering carbon dioxide may include at least one amine, which may be cyclic or acyclic in nature. Suitable amines may include at least one primary amino group and / or at least one secondary amino group, each of which contains a replaceable hydrogen atom to promote the formation of a reaction product with carbon dioxide. Specifically, when carbon dioxide is contacted with the at least one amine, the primary or secondary amino groups may form a carbamate reaction product. Suitable amines for capturing carbon dioxide may include, but are not limited to, pyrrolidine, piperazine, piperidine, morpholine, N-methylpiperazine, N-ethylpiperazine, N-(2-hydroxyethyl)piperazine, N-(2-aminoethyl)piperazine, ethanolamine, diethanolamine, ethylaminoethanol, 1-amino-2-methylpropan-2-ol, 2-amino-1-butanol, 2-(2-aminoethoxy)ethanol, 2-(2-aminoethoxy)ethylamine, hexamethylenediamine (1,6-diaminohexane), pentamethylenediamine (1,5-diaminopentane), tetramethylenediamine (1,4-diaminobutane), 1,3-diaminopropane, 3-(methylamino)propylamine, N-(2-hydroxyethyl)ethylenediamine, 3-(dimethylamino)propylamine, 3-(diethylamino)propylamine, N,N'-bis(2-hydroxyethyl)-ethylenediamine, and the like.

[0041] In a more specific example, the acidic gas capture agent reactive to carbon dioxide may include piperazine. Piperazine is advantageous in this regard due to its low cost, ready availability, and high thermal stability. Reaction 5 below shows how piperazine is believed to react with carbon dioxide to promote its sequestration.

[0042]

[0043] Amines can also be used to trap hydrogen sulfide, particularly by acid-base reactions that protonate the amines and deprotonate the hydrogen sulfide. Therefore, it should be understood that amines can also be used to trap hydrogen sulfide in the second stage of treatment. However, it is more desirable that the second treatment stage can promote the trapping of hydrogen sulfide in a manner other than by acid-base reactions. In particular, the second treatment stage used in the disclosure herein may include at least one acid gas capture agent that is reactive to hydrogen sulfide by nucleophilic aromatic substitution. Suitable acid gas capture agents that react with hydrogen sulfide by nucleophilic aromatic substitution under suitable conditions may include various halogenated benzenes, such as 4-bromotoluene, 4-fluorotoluene, 4-fluoronitrobenzene, etc. Halogenated heteroaromatic compounds such as 2-fluoropyridine and 2-chloro-1,3,5-triazine can also be used similarly. Although fluorinated aromatic compounds tend to be more reactive to nucleophilic aromatic substitution, 4-bromotoluene and similar bromobenzene and chlorobenzene compounds may be advantageous due to their lower cost and acceptable reactivity to hydrogen sulfide. Without being limited by theory or mechanism, it is believed that hydrogen sulfide undergoes deprotonation in the presence of an alkali metal base to become a hydrogen sulfide anion in the second processing stage. The hydrogen sulfide anion is a nucleophile, which can then displace the halogen atom from the halobenzene to form the corresponding thiol-substituted benzene. The thiol-substituted benzene can in turn undergo deprotonation in the presence of an alkali metal base, and the deprotonated thiol group can react as a nucleophile with a second equivalent of the halobenzene to form the corresponding thioether. Reaction 6 below shows the net reaction that occurs when hydrogen sulfide is sequestered with p-bromotoluene in the presence of an alkali metal base.

[0044]

[0045] In view of the foregoing, the present disclosure also provides a method for treating a location containing barite scale to promote dissolution of at least a portion of the barite scale therefrom. More specifically, such a method may include introducing an aqueous fluid composition as described herein to a location containing barite scale, and contacting the barite scale with the aqueous fluid composition for a sufficient time to dissolve at least a portion of the barite scale.

[0046] It should be understood that the dissolution rate of barite scale may depend at least in part on the temperature of the location where the barite scale exists. In a non-limiting example, the temperature of the location may be in the range of from room temperature (23°C) to a maximum of about 200°C, or from about 50°C to about 180°C, or from about 80°C to about 150°C, or from about 95°C to about 135°C, or from about 100°C to about 125°C. The suitable time (immersion time) for contact of the barite scale with the aqueous fluid composition may be from about 30 minutes to about 1 hour, or from about 1 hour to about 12 hours, or from about 2 hours to about 10 hours, or from about 4 hours to about 8 hours. The selected time for contact of the aqueous fluid composition with the barite scale may be selected to obtain a saturated or unsaturated concentration of a water-soluble barium salt in the aqueous fluid composition when at least partial dissolution of the barite scale occurs.

[0047] The contact of the barite scale with the aqueous fluid composition can occur under static or non-static (flowing) conditions. When non-static contact is performed, the aqueous fluid composition can be recycled to the barite scale if desired, as long as the aqueous fluid composition still retains the ability to promote additional dissolution of the barite scale.

[0048] The method of the present disclosure may also include carrying out a second stage treatment at a location containing barite scale to capture at least a portion of at least one acid gas present therein. More specifically, the method of the present disclosure may further include introducing a fluid composition comprising at least one acid gas capture agent into the location, and reacting the at least one acid gas capture agent with at least a portion of at least one acid gas present at the location. The acid gas captured at this location may contain at least hydrogen sulfide, optionally further combined with carbon dioxide. The hydrogen sulfide captured at the location may be derived from sulfate in the aqueous fluid composition reduced with iodide. Optionally, the additional hydrogen sulfide at the location may be derived from a source different from the barite that undergoes dissolution with the aqueous fluid composition.

[0049] The second stage treatment containing at least one acid gas capture agent can be separately introduced into the position containing barite scale (optionally, after the dissolution of barite scale is basically completed), or the second stage treatment can be combined with the aqueous fluid composition at a certain time before the barite scale dissolution is completed. In non-limiting examples, the second stage treatment can be introduced into the position after the aqueous fluid composition has begun to contact barite scale for about 1 hour, or about 2 hours, or about 3 hours, or about 4 hours, or about 5 hours, or about 6 hours. The selected time for introducing the second stage treatment can be selected in response to how much barite scale dissolution and acid gas generation have occurred. For example, the acid gas level during the initial stage of barite dissolution can be maintained at a level without problems, until a greater degree of barite dissolution occurs or until the extraction of wastewater fluid composition needs to be carried out.

[0050] In another case, the first treatment stage and the second treatment stage can be combined with each other before contacting the barite scale. Such a combined fluid can include a concentrated mineral acid (e.g., hydroiodic acid), a first salt including an iodide anion (e.g., an alkali metal iodide), a second salt including an anion that forms a water-soluble barium salt (e.g., a hypophosphite salt), and at least one acid gas capture agent (e.g., a halogenated benzene, an amine, or any combination thereof).

[0051] The location containing the barite scale is not particularly limited and may include any of a formation, a wellbore penetrating the formation, a downhole tool within a wellbore penetrating the formation, a factory, a pipeline, or any combination thereof.

[0052] It should also be understood that the barite scale dissolution in the disclosure herein can occur with the aqueous fluid composition in the presence of formation water, crude oil, or any combination thereof. If desired, the concentration of the active component in the aqueous fluid composition can be increased to promote the effective dissolution of barite scale in the presence of formation water and / or crude oil.

[0053] Embodiments disclosed herein include:

[0054] A. An aqueous fluid composition effective for dissolving barite scale. The aqueous fluid composition comprises: a concentrated inorganic acid; a first salt comprising an iodide anion; and a second salt comprising an anion that forms a water-soluble barium salt.

[0055] B. Scale dissolution system. The scale dissolution system comprises: a first treatment stage comprising an aqueous fluid composition comprising: a concentrated mineral acid; a first salt comprising an iodide anion; and a second salt comprising an anion that forms a water-soluble barium salt; and a second treatment stage comprising a fluid composition comprising at least one acidic gas capture agent.

[0056] C. A method for removing barite scale. The method comprises: introducing an aqueous fluid composition into a location containing barite scale, the aqueous fluid composition comprising: a concentrated inorganic acid; a first salt comprising an iodide anion; and a second salt comprising an anion that forms a water-soluble barium salt; and contacting the barite scale with the aqueous fluid composition for a sufficient time to dissolve at least a portion of the barite scale.

[0057] Each of embodiments A, B and C may have one or more of the following additional elements in any combination:

[0058] Element 1: wherein the concentrated inorganic acid comprises hydroiodic acid.

[0059] Element 2: wherein the second salt is a reducing agent.

[0060] Element 3: wherein the second salt comprises hypophosphite.

[0061] Element 4: wherein the molar ratio of hydroiodic acid to hypophosphite in the aqueous fluid composition is about 5 or greater, and / or the molar ratio of total iodide ions to hypophosphite in the aqueous fluid composition is about 5 or greater.

[0062] Element 5: wherein the first salt comprises an alkali metal iodide.

[0063] Element 6: wherein the second salt comprises an alkali metal hypophosphite.

[0064] Element 7: wherein the first salt comprises an alkali metal iodide, and the second salt comprises an alkali metal hypophosphite.

[0065] Element 7A: wherein the first salt comprises an alkali metal iodide, the second salt comprises an alkali metal hypophosphite, and the concentrated inorganic acid comprises hydroiodic acid.

[0066] Element 7B: wherein the concentrated inorganic acid comprises hydroiodic acid and the second salt comprises hypophosphite.

[0067] Element 7C: wherein the concentrated inorganic acid comprises hydroiodic acid and the first salt comprises an alkali metal iodide.

[0068] Element 8: wherein the at least one acid gas capture agent in the second processing stage comprises at least one first component reactive with hydrogen sulfide.

[0069] Element 9: wherein at least one acid gas capture agent in the second process stage further comprises a second component reactive to carbon dioxide.

[0070] Element 10: wherein the second component comprises at least one amine.

[0071] Element 11: wherein the first component is reactive toward hydrogen sulfide by nucleophilic aromatic substitution.

[0072] Element 12: wherein the first component comprises para-bromotoluene.

[0073] Element 13: wherein the method further comprises: introducing a fluid composition comprising at least one acid gas capture agent into the location; and reacting the at least one acid gas capture agent with at least a portion of the at least one acid gas present at the location.

[0074] Element 14: wherein the at least one acid gas comprises hydrogen sulfide, carbon dioxide or any combination thereof.

[0075] Element 15: wherein the at least one acid gas comprises at least hydrogen sulfide, and at least a portion of the hydrogen sulfide is formed when barite scale contacts the aqueous fluid composition.

[0076] Element 16: wherein at least one acid gas capture agent in the fluid composition comprises a first component reactive to hydrogen sulfide and optionally a second component reactive to carbon dioxide.

[0077] Element 17: wherein the location is a subterranean formation, a wellbore penetrating a subterranean formation, a pipeline, or any combination thereof.

[0078] Non-limiting exemplary combinations that may be applied to A, B, and C include, but are not limited to: 1 and 2; 1 and 3; 1 and 4; 1 and 5; 1 and 6; 1 and 7, 7A, 7B, or 7C; 2 or 3, and 4; 2 or 3, and 5; 2 or 3, and 6; 2 or 3, and 7, 7A, 7B, or 7C; 4 and 5; 4 and 6; and 4 and 7, 7A, 7B, or 7C. Other non-limiting exemplary combinations suitable for B include, but are not limited to: 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 8; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 8 and 9; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 8 to 10; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 8 and 11; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 8, 11 and 12; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 8 and 12; 8 and 9; 8 to 10; 8, 9 and 11; 8 and 11; 8, 11 and 12; and 8 and 12. Other non-limiting exemplary combinations suitable for C include, but are not limited to, 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 13; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 13 and 14; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 13 and 15; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 13 and 16; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 13 and 17; 1, 3, 4, 5, 6, 7, 7A, 7B or 7C, and 13 and 17; 13 and 14; 13 and 15; 13 and 16; 13 and 17; 10, 13 and 16; 11, 13 and 16; and 10, 11, 13 and 16.

[0079] In order to facilitate a better understanding of the disclosure herein, the following examples of various representative embodiments are given. The following examples should not be understood as limiting or defining the scope of the present disclosure.

[0080] Example

[0081] Materials and reagents. All glassware used in chemical preparations were cleaned with 10% (v / v) HCl and rinsed three times with sterile 18 MΩ water before use. Industrial or synthetic grade barite (BaSO4-98.5%) scale crystals were purchased from Chemi-Enterprise, India. Typical reservoir or backhole barite scale was obtained from a representative oil well of Saudi Aramco. The downhole barite scale contained 96.2% barite and 3.8% quartz, CaCO3 and FeCO3 by weight. Reagent grade hydroiodic acid (HI, 67% by weight), potassium iodide (KI, 99%), sodium hypophosphite monohydrate (NaH2PO2·H2O, ≥99%), sodium hydroxide (NaOH, 99%) and isopropanol were purchased from Sigma-Aldrich. Bromotoluene (C7H7Br, 98%) and piperazine (C4H 10 N2, 97%) was purchased from Fischer Scientific.

[0082] Stage 1 treatment: Preparation of a representative aqueous fluid composition for barite scale removal. Potassium iodide (KI, 46 g, 0.28 mol) was placed in a 1 L two-necked round bottom flask equipped with a reflux condenser, a magnetic stirrer, a glass thermometer and an inlet funnel. Hydroiodic acid (HI, 67% w / v, density = 1.95-2.02 g / cm 3 , 400mL, about 4.13mol iodide ion). The flask was placed on a heating mantle and the mixture was subjected to reflux distillation at a temperature of 128°C while continuously stirring with a magnetic stirring bar to remove non-condensable and volatile iodine-containing substances, respectively. Sodium hypophosphite monohydrate (NaH2PO2·H2O, 82g, 0.77mol) was then added to the reaction mixture. A stream of N2 was continuously bubbled into the reaction mixture to prevent the ingress of oxygen. During the 3-hour reflux distillation in the presence of sodium hypophosphite monohydrate, the reaction mixture changed from the initial dark yellow to a colorless state (thought to be due to I2 or I3 - Restore to I - The reaction mixture was then cooled under N2 flow for 1 hour and used directly in the following further experiments. Other aqueous fluid compositions containing different amounts of the aforementioned components were similarly prepared.

[0083] Second stage treatment: Preparation of a representative fluid composition for acid gas capture in conjunction with barite scale removal. An equimolar mixture of p-bromotoluene and piperazine was stirred in 350 mL of isopropanol in a 1 L flask at room temperature for 1 hour. A white solution was obtained. After the initial 1 hour stirring period, 10% sodium hydroxide solution was added to the white solution to form a colorless solution, which was then used directly in further experiments below.

[0084] Barite dissolution conditions. Barite dissolution tests were performed using double-jacketed glassware and a hot plate set to maintain static temperature conditions. Barite dissolution was performed at temperatures of 100°C and 130°C (representing shallow and deep oil and gas wells, respectively) with immersion times of 0, 2, 4, 6, 8, and 10 hours. Synthetic industrial grade barite ( Figure 1 SEM images shown in ) and downhole barite scale ( Figure 2 The SEM images shown in Figure 1 were obtained by cleaving the barite surface with a razor blade and polishing before each experiment. Additional dissolution experiments were conducted in the presence of 15% formation water or 15% crude oil to determine the effects of these components on barite dissolution. Barite dissolution under each set of conditions was determined gravimetrically.

[0085] Figure 3 is a graph of barite solubility as a function of immersion time under various conditions. Figure 3 The data shown is for synthetic industrial grade barite in the absence of formation water or crude oil hydrocarbons. As shown, the amount of dissolved barite increases with time, and dissolution also increases with temperature. At 130°C and 100°C, the maximum solubility is 90.5 g / L and 72.0 g / L, respectively. Figure 4 The figure is a comparison of the solubility of synthetic industrial grade barite with that of downhole barite scale at 100°C and 130°C with an 8-hour soak time. As shown in the figure, the barite solubility caused by downhole barite scale is lower than that of synthetic industrial grade barite at 100°C and 130°C. The maximum barite solubility of both samples at 130°C is 10%-12% higher than that at 100°C.

[0086] Figure 5 is a graph comparing the solubility of downhole barite scale alone at 130°C to the solubility measured under similar conditions in the presence of formation water or crude oil. The soak time was 10 hours and the barite scale was present at 70% w / v relative to the formation water or crude oil. The aqueous fluid compositions were tested at the concentrations prepared above at a set volume (1X volume) and twice the set volume (2X volume). As shown, both formation water and crude oil reduce the solubility of barite, but the reduction in solubility is less pronounced when the volume of the aqueous fluid composition is doubled (2X volume).

[0087] Acid Gas Release. When downhole barite scale is dissolved with the aqueous fluid composition disclosed above, about 5% H2S and about 3% CO2 by mass relative to the barite are released. The acid gas is captured using the second stage process described above. Briefly, acid gas capture is performed after contact between the barite scale and the first stage aqueous fluid composition described above at 130°C for 4 to 6 hours. During the barite dissolution process, H2S and CO2 concentrations are monitored in situ using an electrochemical analyzer, and acid gas capture is performed once both concentrations approach 2.5 mol%, such as Figure 6 After about 4 hours of soaking, when both acid gases reached the aforementioned threshold concentrations, the second stage treatment (67 mL) was added dropwise to the reaction mixture (1 L of the first stage treatment) via a peristaltic pump through the coil. The second stage treatment was effective in substantially preventing the release of acid gases, as shown by the subsequent decrease in acid gas concentrations over time. In the wellbore, the second stage treatment can be obtained during flowback to recover acid gases trapped therein.

[0088] The terms used herein are only for the purpose of describing specific embodiments, not for limiting the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that when the terms "comprise", "contain" and / or "include" and their variations are used in this specification, they specify the presence of the features, wholes, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements and / or parts.

[0089] The directional terms used herein are for convention and reference purposes only and should not be construed as limiting. However, it should be recognized that these terms may be used with reference to an operator or user. Therefore, no limitation is implied or inferred. In addition, the use of ordinal numbers (e.g., first, second, third) is for distinction rather than counting. For example, the use of "third" does not mean that there is a corresponding "first" or "second". Moreover, the words and terms used herein are for descriptive purposes and should not be considered limiting. "Include," "comprising," "having," "containing," "involving," and variations thereof as used herein are meant to cover the items listed thereafter and their equivalents as well as additional items.

[0090] Although the present disclosure has described several exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and that equivalents may be substituted for its elements without departing from the spirit and scope of the present disclosure. In addition, it will be appreciated by those skilled in the art that many modifications will adapt specific instruments, situations or materials to the embodiments of the present disclosure without departing from the essential scope of the present disclosure. Therefore, the present invention is not limited to the specific embodiments disclosed, or the best mode for carrying out the present invention, but the present invention will include all embodiments falling within the scope of the appended claims.

[0091] While the present disclosure has been described with reference to a limited number of embodiments, those skilled in the art having benefit of this disclosure will appreciate that other embodiments can be designed which do not depart from the scope of the present disclosure as described herein. Accordingly, the scope of the present disclosure should be limited only by the claims appended hereto.

[0092] All documents described herein are incorporated herein by reference for the purpose of all jurisdictions allowing such practice, including any priority documents and / or test procedures, as long as they do not contradict this article. As is apparent from the general description and specific embodiments above, although the form of the present disclosure has been illustrated and described, various modifications can be made without departing from the thought and scope of the present disclosure. Therefore, it is not intended to limit the present disclosure thereby. For example, the composition described herein may not contain any component or composition not explicitly listed or disclosed herein. Any method may lack any step not listed or disclosed herein. Similarly, the term "including" is considered to be synonymous with the term "comprising". As long as there is a transitional phrase "including" before a method, composition, element or element group, it should be understood that we also contemplate that the same composition or element group has a transitional phrase "substantially consisting of...", "consisting of...", "selected from a group consisting of..." or "is", before the narration of the composition, element or multiple elements, and vice versa.

[0093] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and the like used in the specification and the associated claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and the appended claims are approximations that may vary depending upon the desired properties sought to be obtained by one or more of the embodiments described herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0094] When a numerical range with a lower limit and an upper limit is disclosed, any numerical value and any included range falling within the range are specifically disclosed. In particular, each numerical range disclosed herein (in the form of "from about a to about b", or equivalently, "from about a to b", or equivalently, "from about ab") should be understood to set forth each number and range contained within the wider numerical range. Moreover, the terms in the claims have their direct, ordinary meanings unless otherwise explicitly and clearly defined by the patentee. In addition, the indefinite article "a" used in the claims is defined herein as one or more than one of the elements it introduces.

[0095] One or more illustrative embodiments are presented herein. For the sake of clarity, all features of physical implementation are not described or shown in this application. It should be understood that in the development of the physical embodiments of the present disclosure, many implementation-specific decisions must be made to achieve the developer's goals, such as meeting system-related, business-related, government-related and other constraints, which vary with implementation and time. Although the developer's efforts may be time-consuming, this effort will be a routine task for those of ordinary skill in the art who benefit from the present disclosure.

[0096] Therefore, the present disclosure is well adapted to obtain the objects and advantages mentioned and inherent therein. The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art and with the benefit of the teachings herein. In addition, no limitation is intended to the details of construction or design shown herein except as described in the following claims. Therefore, it is apparent that the particular illustrative embodiments disclosed above may be altered, combined or modified, and all such variations are considered to be within the scope and spirit of the present disclosure. The embodiments disclosed herein for illustration purposes may be appropriately implemented in the absence of any element not specifically disclosed herein and / or in the absence of any optional element not disclosed herein.

Claims

1. An aqueous fluid composition comprising: concentrated mineral acids; a first salt comprising an iodide anion; and A second salt comprises an anion that forms a water-soluble barium salt.

2. The aqueous fluid composition according to claim 1, wherein The concentrated mineral acid includes hydroiodic acid.

3. The aqueous fluid composition according to claim 2, wherein The second salt is a reducing agent.

4. The aqueous fluid composition according to claim 2, wherein The second salt comprises a hypophosphite salt.

5. The aqueous fluid composition according to claim 4, wherein The molar ratio of hydroiodic acid to hypophosphite in the aqueous fluid composition is about 5 or greater, and / or the molar ratio of total iodide ions to hypophosphite in the aqueous fluid composition is about 5 or greater.

6. The aqueous fluid composition according to claim 1, wherein The first salt comprises an alkali metal iodide.

7. The aqueous fluid composition according to claim 6, wherein The second salt comprises an alkali metal hypophosphite.

8. The aqueous fluid composition according to claim 7, wherein The concentrated mineral acid includes hydroiodic acid.

9. The aqueous fluid composition according to claim 8, wherein The molar ratio of hydroiodic acid to alkali metal hypophosphite in the aqueous fluid composition is about 5 or greater, and / or the molar ratio of total iodide ions to alkali metal hypophosphite in the aqueous fluid composition is about 5 or greater.

10. A scale dissolving system comprising: A first processing stage comprising an aqueous fluid composition comprising: concentrated mineral acids; a first salt comprising an iodide anion; and a second salt comprising an anion that forms a water-soluble barium salt; and A second treatment stage includes a fluid composition comprising at least one acid gas capture agent.

11. The scale dissolving system according to claim 10, wherein: The concentrated mineral acid includes hydroiodic acid.

12. The scale dissolving system according to claim 11, wherein: The second salt comprises a hypophosphite salt.

13. The scale dissolving system according to claim 12, wherein: The molar ratio of hydroiodic acid to hypophosphite in the first treatment stage is about 5 or greater, and / or the molar ratio of total iodide ions to hypophosphite in the first treatment stage is about 5 or greater.

14. The scale dissolving system according to claim 11, wherein: The first salt comprises an alkali metal iodide, and the second salt comprises an alkali metal hypophosphite.

15. The scale dissolving system according to claim 10, wherein: The at least one acid gas capture agent in the second processing stage includes at least one first component reactive toward hydrogen sulfide.

16. The scale dissolving system according to claim 15, wherein: The at least one acid gas capture agent in the second process stage further comprises a second component reactive toward carbon dioxide.

17. The scale dissolving system according to claim 16, wherein: The second component includes at least one amine.

18. The scale dissolving system according to claim 15, wherein: The first component is reactive toward hydrogen sulfide by nucleophilic aromatic substitution.

19. The scale dissolving system according to claim 18, wherein: The first component includes para-bromotoluene.

20. A method comprising: An aqueous fluid composition is introduced into a location containing barite scale, the aqueous fluid composition comprising: concentrated mineral acids; a first salt comprising an iodide anion; and a second salt comprising an anion that forms a water-soluble barium salt; and The barite scale is contacted with the aqueous fluid composition for a sufficient time to dissolve at least a portion of the barite scale.

21. The method according to claim 20, wherein: The concentrated inorganic acid comprises hydroiodic acid, and the second salt comprises hypophosphite.

22. The method according to claim 21, further comprising: introducing a fluid composition comprising at least one acid gas capture agent into the location; as well as The at least one acid gas capture agent is reacted with at least a portion of at least one acid gas present at the location.

23. The method according to claim 22, wherein: The at least one acid gas includes hydrogen sulfide, carbon dioxide, or any combination thereof.

24. The method according to claim 23, wherein: The at least one acid gas includes at least hydrogen sulfide, and at least a portion of the hydrogen sulfide is formed when the barite scale contacts the aqueous fluid composition.

25. The method according to claim 22, wherein: The at least one acid gas capture agent in the fluid composition includes a first component reactive toward hydrogen sulfide and optionally a second component reactive toward carbon dioxide.

26. The method of claim 20, wherein: The location is a subterranean formation, a wellbore penetrating a subterranean formation, a pipeline, or any combination thereof.

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