Iron sulfide control using an alkali metal or alkaline earth metal peroxymonosulfate

Abstract

Disclosed herein are methods for controlling iron sulfide associated with a wellbore, downhole formation, reservoir or well, or infrastructure or equipment used in the extraction, production, processing, transportation, storage or disposal of a fluid, such as in pipelines and other infrastructure or equipment used in the oil and gas industries, as well as many other industries.

Description

[0001] TITLE

[0002] Iron Sulfide Control Using an Alkali Metal or Alkaline Earth Metal Peroxymonosulfate

[0003] FIELD OF INVENTION

[0004] The present disclosure relates to controlling iron sulfide associated with a wellbore, downhole formation, reservoir, or well, or infrastructure or equipment used in the extraction, production, processing, transportation, storage or disposal of a fluid, such as pipelines and other infrastructure or equipment used in the oil and gas industries, as well as many other industries.

[0005] BACKGROUND OF THE INVENTION

[0006] Iron sulfide formation is a pervasive problem encountered in the oil and gas industries, as well as many others, particularly where iron sulfide becomes dispersed within fluids, forms deposits or scaling to clog porous media or pore spaces of downhole formations or reservoirs, and / or forms deposits or scaling on the surfaces of wellbores, infrastructure or equipment, such as pipel ines, tubings, vessels, injection l ines and other equipment. The accumulation or buildup of iron sulfide can lead to major economic loss and a range of costly and dangerous operational problems. If left untreated, iron sulfide buildup can accelerate corrasion rates, obstruct or plug flow in or from wells, reservoirs lines, injection systems, production systems, disposal systems, processing equipment, etc., interfere with safe operations, among other issues.

[0007] A chemical solution is needed to control iron sulfide associated with such systems, particularly where mechanical cleaning may not be feasible or may be less desirable. In general, conventional cleaners may disperse iron sulfide but are relatively ineffective in inhibiting or dissolving iron sulfide. In addition, conventional cleaners may be acidic and therefore may be incompatible with the metallurgy of the systems they are designed to treat and / or may contribute to the formation of undesirable byproducts and cause corrosion.

[0008] Kotronarou et al., " Peroxymonosulfate: An Alternative to Hydrogen Peroxide for the Control of Hydrogen Sulfide,” Journal of the Water Pollution Control Federation, vol. 63, no. 7 (1991), assessed the effectiveness of peroxymonosulfate for H2S oxidation in wastewater. The reference does not disclose or contemplate the use of peroxymonosulfatc to dissolve iron sulfide particulates.

[0009] U.S. Patent No. 11, 136,491 B2 discloses a method of dissolving iron sulfide on carbon steel tubing to yield chelated iron by treating the carbon steel tubing with a composition including an iron chelant and an additive including at least one of an oxidizing agent and a base. In its disclosed experimental testing, the patent reports that the oxidizer NaNCL improved dissolution performance, whereas the oxidizers KMnO4, NaCIO2. and NaBrO3did not increase dissolution performance of the dissolver. U.S. Patent No. 9,670,080 discloses a method for reducing sulfide in oilfield waste water comprising contacting oilfield waste water with an oxidizer in the presence of an iron catalyst. In particular, the reference reports experimental testing of a combination of chlorine dioxide and ferric sulfate.

[0010] Additionally, it is generally understood that while certain oxidizing agents have been used in the treatment of sulfur-based contaminants, oxidation byproducts are generated, including elemental sulfur which can be corrosive and require additional expensive and / or time-consuming corrective processing steps.

[0011] There remains a need for a chemical solution to control iron sulfide associated with a wellbore, downhole formation, reservoir or well, or infrastructure or equipment used in the extraction, production, processing, transportation, storage or disposal of a fluid. In particular, there remains a need for a chemical agent to remove or dissolve iron sulfide with increased efficiency and preferably where such agent reduces or mitigates the formation or production of elemental sulfur byproduct.

[0012] These needs are met by the presently disclosed invention. In particular, it was surprisingly found in accordance with the present disclosure that an alkali or alkaline earth metal peroxymonosulfate rapidly dissolves iron sulfide at lower concentrations compared to other tested oxidizing agents while also preferably reducing or mitigating the formation or production of elemental sulfur.

[0013] SUMMARY OF INVENTION

[0014] Provided is a method of controlling iron sulfide associated with a wellbore, downhole formation, reservoir or well (e.g., a disposal well), or infrastructure or equipment used in the extraction, production, processing, transportation, storage or disposal of a fluid, the method comprising adding or delivering an effective amount of an alkali metal or alkaline earth metal peroxymonosulfate to a fluid that contacts or flow's or is stored within the wellbore, the dow'nhole formation, reservoir or well or the infrastructure or equipment and controlling iron sulfide w ith the fluid comprising the alkali metal or alkaline earth metal peroxymonosulfate. The peroxymonosulfate can dissolve iron sulfide particles dispersed within a fluid or deposited or scaled on surfaces. The peroxymonosulfate can further inhibit the accumulation of iron sulfide particles, e.g., inhibit the formation of iron sulfide deposits or scaling. The peroxynionosulfate is particularly useful to remove or dissolve iron sulfide deposits or scaling from surfaces (e.g., metal or mineral surfaces) which are contacted with the fluid comprising the peroxymonosulfate, such as metal surfaces of wellbores, infrastructure or equipment, or mineral surfaces, such as those that define pore spaces or comprise porous media, of downhole formations, reservoirs and wells. The peroxymonosulfate is also particularly useful to inhibit iron sulfide formation on surfaces (e.g., metal or mineral surfaces) which are contacted with the fluid comprising the peroxymonosulfate. In this way, the peroxymonosulfate, in addition to providing a cleaning effect, can act as a corrosion inhibitor.

[0015] In particular, the method of the present disclosure is useful to control iron sulfide associated with a wellbore, downhole formation, reservoir or well, or infrastructure or equipment used in the extraction, production, processing, transportation, storage or disposal of fluids in energy-related applications, such as in the oil and gas industries. The method can provide a cleaning effect via the removal or dissolution of iron sulfide, corrosion protection via the inhibition of iron sulfide formation on surfaces, or a combination of both for applications relating to the extraction, production, processing, transportation or storage of oil (whether crude or processed) and natural gas. For example, the method can improve production in an oil and / or gas application by removing iron sulfide deposits or scaling from and / or reducing a corrosion rate of metal surfaces which are contacted by the fluid comprising the alkali metal or alkaline earth metal peroxymonosulfate. The method can enhance oil and gas production by, for example, keeping surface facility equipment, pipelines, downhole injection tubing and infrastructure, and pore throats around an injector clean to accept an optimum water volume.

[0016] The method of the present discl osure is also useful to control iron sulfide associated with infrastructure or equipment in the production, processing, transportation, storage or disposal of a fluid in many other applications or systems, such as coal-fired processes or systems (e.g., a coal-fired power plant), waste- waterprocesses or systems (e.g., municipality waste-water plants), farm processes or systems, slaughter house processes or systems, land-fill processes or systems, coking coal processes or systems, biofuel processes or systems, etc.

[0017] BRIEF DESCRIPTION OF THE FIGURES

[0018] FIG. 1 shows a photograph of samples of an iron sulfide suspension prepared from a culture of Desulfovibrio alaskensis ATCC 14563 and treated with potassium hydrogen peroxymonosulfate at various concentrations versus untreated controls each at room temperature.

[0019] FIG. 2 shows a photograph of samples of an iron sulfide suspension prepared from a culture of Desulfovibrio alaskensls ATCC 14563 and treated with potassium hydrogen peroxymonosulfate at various concentrations versus untreated controls each at elevated temperature.

[0020] DETAILED DESCRIPTION

[0021] Unless otherwise specified, the following terms as used in the present disclosure have the meanings defined below:

[0022] In the context of the present disclosure, “controll ing iron sulfide” refers to removing or dissolving iron sulfide, inhibiting the accumulati on of iron sulfide, or a combination thereof. For example, “controlling iron sulfide” may refer to removing or dissolving dispersed iron sulfide particles or iron sulfide deposited or scaled on a surface (e.g., a metal or mineral surface) which is contacted with the fluid comprising the alkali metal or alkaline earth metal peroxymonosulfate, such as surfaces of wellbores, infrastructure or equipment; removing or dissolving iron sulfide deposits or scaling from downhole formations, reservoirs or wells in contact with the fluid comprising the peroxymonosulfate, such as removing or dissolving deposits or scaling from porous media or pore spaces; inhibiting iron sulfide formation on a surface (e.g.. a metal or mineral surface) which is contacted with the fluid comprising the alkali metal or alkaline earth metal peroxymonosulfate; or to any combination thereof. The surface may be, for example, a surface of a wellbore ( including, but not limited to, casings, tubing, perforated tubing or piping, liners, screens, etc.), or a surface of infrastructure or equipment, such as pipelines, tubings, vessels, tanks, and other infrastructure or equipment.

[0023] The term “effective amount” and the like refer to an amount to provide a desired effect for controlling iron sulfide.

[0024] The alkali metal or alkaline earth metal peroxymonosulfate is chemically representable as MaHb(SO5)cwhere M is an alkali metal in Group 1 a of the Periodic Table or an alkaline earth metal in Group 1b of the Periodic Table where a, b, and c are integers. Integers a, b, and c satisfy the relationship na + b equals 2c where n is an integer equal to 1 for an alkali metal or equal to 2 for an alkaline earth metal. Integer b can be 0 such that hydrogen is absent in the Hbterm of MaHb(SO5)c.

[0025] The alkali metal peroxymonosulfates include alkali metal hydrogen peroxymonosulfates and dialkali metal peroxymonosulfates. Preferred alkali metals are sodium, potassium, lithium or any combination thereof, more preferably potassium. For primary alkali metals potassium, sodium and lithium, the alkali metal peroxymonosulfates are potassium hydrogen peroxymonosulfate (KHSO5), dipotassium peroxymonosulfate (K2SO5), sodium hydrogen peroxymonosulfate (NaHSO5), disodium peroxymonosulfate (Na2SC5), lithium hydrogen peroxymonosulfate (LiHSO5), and dilithium peroxymonosulfate (Li2SO5). Preferred alkaline earth metals are calcium, magnesium or a combination thereof. For primary alkaline earth metals magnesium and calcium, the alkaline earth metal peroxymonosulfates are magnesium peroxymonosulfate (MgSO5), magnesium dihydrogen diperoxymonosulfate (MgH2(SO5)2), calcium peroxymonosulfate (CaSO5), and calcium dihydrogen diperoxymonosulfate (CaH2(SO5)2) .

[0026] Preferably, the peroxymonosulfate is potassium hydrogen peroxymonosulfate (KHSO5). In preferred embodiments, the potassium hydrogen peroxymonosulfate is provided as a component of a multiple salt (i.e., the multiple salt comprises potassium hydrogen peroxymonosulfate). The multiple salt is preferably a potassium monopersulfate which is characterized by a hydrogen-bonded structure of potassium hydrogen peroxymonosulfate (KHSO5), potassium hydrogen sulfate (KHSO4) and potassium sulfate (K2SO4), commonly referred to as a triple salt and can be represented by the general formula (KHSO5)x(KHSO4)y(K2SO4)zfor which the sum of mole fractions x, y, and z equals 1. The active oxygen component of the potassium monopersulfate triple salt is potassium hydrogen pcroxymonosulfatc (KHSO5). Such triple salts are commercially available or can be prepared by known methods. The mole fraction x is often at least about 0.40, more preferably at least about 0.43, or at least about 0.46. In general, the mole fractions may be represented by the following exemplary ranges: x is about 0.43-0.64, y is about 0. 15-0.43, and z is about 0.15-0.43, particularly where x is about 0.46-0.64, y is about 0.15-0.37, and z is about 0. 15-0.37.

[0027] In a particular example, the potassium monopersulfate used in the presently disclosed methods is commonly represented by the formula 2KHSO5.KHSO4.K2SO4(corresponding to theoretical mole fractions x, y, z above of 0.5, 0.25 and 0.25, respectively) and which are particular implementations of the more general triple salt formula above. These embodiments have a theoretical active oxygen content of 5.2%, and commercial versions thereof often have an active oxygen content close to this theoretical value, such as an active oxygen content of at least about 4.5%, for example an active oxygen content of about 4.7%. Reference herein to the potassium monopersulfate triple salt of the formula 2KHSO5.KHSO4.K2SO4is intended to be inclusive of such embodiments having an active oxygen content close to the theoretical active oxygen content of 5.2%, such as the commercial versions thereof. The potassium monopersulfate triple salts of the present disclosure may have an active oxygen content greater than the about 4.7% active oxygen content which is typically found in commercially available potassium monopersulfate triple salts. Such triple salts may be prepared as known in the art, such as described in U.S. Pat. No. 7,090,820.

[0028] In general, the potassium monopersulfate triple salts of the present disclosure have an active oxygen content of at least about 4.0%, preferably at least about 4.5%, or more preferably at least about 4.7%. For example, the active oxygen content may be from about 4.0%, from about 4.5% or from about 4.7% to about 6.8%, to about 6.2%, to about 5.5% or to about 5.2%.

[0029] A potassium monopersulfate triple salt commonly represented by the formula 2KHSO5.KHSO4.K2SO4is available commercially under the brand name OXONE®.

[0030] The peroxymonosulfate or multiple salt containing the same, such as a potassium monopersulfate triple salt, may be in a solid (e.g., crystalline) form or in a formulated solid or liquid form, such as a liquid solution (e.g., an aqueous solution).

[0031] The peroxymonosulfate (or multiple salt containing the same) may be a component of a composition that is added to the fluid. The composition may further comprise at least one other iron sulfide- dissolving compound and / or one or more other additives, such as corrosion inhibitors, asphaltene inhibitors, paraffin inhibitors, scale inhibitors, emulsifiers, water clarifiers, dispersants, emulsion breakers, hydrogen sulfide scavengers, friction reducers, oxygen scavengers, gas hydrate inhibitors, biocides, pH modifiers, and surfactants. In one aspect of the present disclosure, the composition comprising the alkali metal or alkaline earth metal peroxymonosulfate is free or substantially free of an iron chelator. For example, the alkali metal or alkaline earth metal peroxymonosulfate can be used without combination with an iron chelator, or the presently disclosed method can control iron sulfide without the addition of an iron chelator to the fluid that contacts or flows or is stored within the wellbore, the downhole formation, reservoir or well, or the infrastructure or equipment. In another aspect, the composition comprising the alkali metal or alkaline earth metal peroxymonosulfate is free or substantially free of an iron catalyst. For example, the alkali metal or alkaline earth metal peroxymonosulfate can be used without combination with an iron catalyst, or the presently disclosed method can control iron sulfide without the addition of an iron catalyst to the fluid that contacts or flow's or is stored within the wellbore, the downhole formation or reservoir or the infrastructure or equipment. In a further aspect, the composition comprising the alkali metal or alkaline earth metal peroxymonosulfate is free or substantially free of an iron chelator and an iron catalyst. For example, the alkali metal or alkaline earth metal peroxymonosulfate can be used without combination with an iron chelator or an iron catalyst, or the presently disclosed method can control iron sulfide without the addition of an iron chelator or an iron catalyst to the fluid that contacts the wellbore, the downhole formation or reservoir or the infrastructure or equipment.

[0032] In the method of the present disclosure, iron sulfide associated with a w'ellbore, downhole formation, reservoir or well (e.g., a disposal well), or infrastructure or equipment used in the extraction, production, processing, transportation, storage or disposal of a fluid is controlled by adding or delivering an effective amount of an alkali metal or alkaline earth metal peroxymonosulfate to a fluid that contacts or flows or is stored within the wellbore, the downhole formation, reservoir or well, or the infrastructure or equipment. The effective amount of the alkali metal or alkaline earth metal peroxymonosulfate may be chosen to provide a desired concentration for controlling iron sulfide, and the treatment can occur for a desired period of time (including at desired frequencies or intervals). For example, the effective amount may provide from about 50 ppm to about 10000 ppm, such as from about 50 ppm, from about 100 ppm, from about 250 ppm, from about 500 ppm or from about 1000 ppm to about 10000 ppm, to about 5000 ppm, or to about 3000 ppm of the alkali metal or alkaline earth metal peroxymonosulfate, such as potassium hydrogen peroxymonosulfate (KHSO5). Where the effective amount of potassium hydrogen peroxvmonosulfate (KHSO5) is provided from a potassium monopersulfate triple salt as described herein, the addition step may provide from about 100 ppm to about 20000 ppm, such as from about 100 ppm, from about 200 ppm, from about 500 ppm, from about 1000 ppm or from about 2000 ppm to about 20000 ppm, to about 10000 ppm or to about 6000 ppm of the potassium monopersulfate triple salt. It shall be understood that the foregoing ranges are exemplary only. Other amounts or concentrations may be applied. Based on the particular system and the site targeted for treatment, the skilled person will be able to determine an appropriate amount of the alkali metal or alkaline earth metal pcroxymonosulfate (or multiple salt containing the same) for addition to the fluid, as well as appropriate addition times, frequencies, and / or intervals, to control iron sulfide in the targeted system.

[0033] To control iron sulfide in accordance with the present disclosure, the alkali metal or alkaline earth metal peroxymonosulfate is added to a fluid that contacts or flows or is stored within a wellbore, downhole formation, reservoir or well, or infrastructure or equipment, such as described herein. The fluid to which the alkali metal or alkaline earth metal peroxymonosulfate is added (i.e., the fluid comprising the alkali metal or alkaline earth metal peroxymonosulfate) may contact a surface of a wellbore, typically a metal or mineral surface, such as metal surfaces of casings, tubing, perforated tubing or piping, liners, screens, etc. The wellbore may be, for example, an injection well, production well, disposal well or fracturing well. The fluid comprising the alkali metal or alkaline earth metal peroxymonosulfate may contact a mineral surface of a downhole formation, reservoir or well, such as mineral surfaces defining pore spaces or comprising porous media, such as relevant to the flow of injection, formation, flowback and / or production fluids. The fluid comprising the alkali metal or alkaline earth metal peroxymonosulfate may contact a surface, typically a metal surface, of infrastructure or equipment (whether topside or downhole or in applications other than oil turd gas), such as pipelines (e.g., pipelines connecting tanks, vessels or processing units), tubing, such as downhole injection tubing, vessels, such as transportation, cargo or storage vessels, underground structures, holding tanks, mixing tanks, water lowers, flow lines, injection lines, production lines, pumps, scrubbers (e.g., a wet flue gas desulfurizer, a spray dry absorber, a dry sorbent injector, a spray tower, a contact or bubble tower, or the like), heat exchangers, etc. The metal surface may comprise steel, carbon steel, mild steel, etc., such as stainless steel surfaces of wellbores, stainless steel conduit or pipeline, carbon steel conduit or pipeline, mild steel conduit or pipeline, etc.

[0034] The infrastructure or equipment may, for example, transport the fluid from one point to another, such as an oil and / or gas pipeline. The infrastructure or equipment can be part of a petroleum (e.g., oil and / or gas) refinery, such as a pipeline, a separation vessel, a storage tank, a dehydration unit, or a gas line. The infrastructure or equipment may be used in petroleum (e.g., oil and / or gas) extraction or production, such as a wellhead. The infrastructure or equipment can be part of a coal-fired power plant.

[0035] The fluid may be a gas, a liquid or a combination thereof. For example, the fluid may be associated with infrastructure or equipment of a water system, an oil system, a gas system, a phase change or heat transfer system (e.g., condensate fluids) or any combination thereof. The fluid may be an aqueous fluid or medium or an oil / brine mixture. The aqueous medium can comprise gas and / or liquid hydrocarbons. The fluid may comprise at least one of injection water, formation water, produced water, flowback water, waste water, cooling water, or source water, such as pond water or holding tank water.

[0036] The fluid may comprise natural gas or a liquid hydrocarbon, such as a crude oil based or refined oil based stream. The liquid hydrocarbon can be any type of liquid hydrocarbon. For example, the liquid hydrocarbon may comprise crude oil, heavy oil, processed residual oil, bituminous oil, coker oil, gas oil, fluid catalytic cracker feed or slurry, naphtha, diesel fuel , fuel oil, jet fuel, gasoline, or kerosene. The fluid can be a refined hydrocarbon product.

[0037] The fluid may be a gas, liquid or combination thereof produced or used in the extraction, production, processing, transportation or storage of etude or refined oil or natural gas. The fluid may comprise other types of fuels, such as hydrogen (e.g,, in the transportation or storage of hydrogen, such as subsurface storage).

[0038] The fluid may be a gas stream used or produced in a coal-fired process, such as a coal-fired power plant or the fluid may be a gas, liquid or combination thereof produced or used in a waste-water process, a farm, a slaughter house, a landfill, a municipality waste-water plant, a coking coal process, or a biofuel process.

[0039] The present application is not limited to any specific technique for adding or delivering the alkali metal or alkaline earth metal peroxymonosulfate to the fluid, and the exact manner of addition or delivery will depend on various factors, such as the form or formulation of the alkali metal or alkaline earth metal peroxymonosulfate, the particular system and the site of interest. In general, the alkali metal or alkaline earth metal pcroxymonosulfatc is added such that it is or becomes mixed with or dissolved w ithin the fluid for providing treatment at the site of interest.

[0040] The alkali metal or alkaline earth metal peroxymonosulfate can be added at a point in a flow line upstream from the point at which controlling iron sulfide is desired. It may be injected, for example, using mechanical equipment such as chemical injection pumps, piping tees, injection fittings, atomizers, quills, and the like. The peroxymonosulfate may be added using an umbilical line or using a capillary injection system.

[0041] The peroxymonosulfatc can be added to the fluid continuously, in batch (e.g., intermittent batch treatment, whether during operation or during a shutdown period), or a combination thereof (such as continuous treatment during operation and a batch treatment during a shutdown period). The doses can be continuous / maintained and / or intermittent to both remove or dissolve iron sulfide particles and / or inhibit iron sulfide formation.

[0042] As used herein, the articles “a”, “an”, and “the” preceding an element or component of the invention are intended to be nonrestrictive regarding the number of instances (i.e., occurrences) of the element or component. Therefore “a”, “an”, and “the” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously' meant to be singular.

[0043] As used herein, the term “comprising” means the presence of the stated features, integers, steps, or components as referred to in the claims, but that it does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. The term “comprising” is intended to include embodiments encompassed by the terms “consisting essentially of' and “consisting of'. Similarly, the term “consisting essentially of’ is intended to include embodiments encompassed by the term “consisting of’.

[0044] As used herein, the term “about” modifying the quantity of an ingredient or reactant employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or use solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods; and the like.

[0045] Where present, ail ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, and the like.

[0046] When a parameter is given either as a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges arc separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. The scope of the invention is not intended to be limited to the specific values and examples as recited in the specification.

[0047] EXAMPLES

[0048] Example 1. Iron sulfide dissolution with potassium hydrogen peroxymonosulfate (KHSO5)

[0049] Materials:

[0050] Sulfate reducing bacteria: Desulfovibrio alaskensis ATCC 14563.

[0051] Culture medium 1250: Modified Barr’s Medium with 2.5% NaCl (ATCC Medium 1250) amended with 0.01% of ferrous ammonium sulfate hexahydrate.

[0052] Iron sulfide suspension: Desulfovibrio alaskensis ATCC 14563 grown in Culture medium 1250 at 30°C for 3 days. 200 ml of the culture was centrifuged at 1000g for 5 minutes and the precipitate collected. The precipitate was resuspended in 110 ml of deionized water.

[0053] Potassium hydrogen peroxymonosulfate (KHSO5) was provided in the form of a potassium monopersulfate triple salt (available under the brand name OXONE®and commonly represented by the formula 2KHSO5.KHSO4.K2SO4). Two solutions were prepared in deionized water at a concentration of 2500 ppm potassium monopersulfate triple salt (1250 ppm of KHSO5) and 625 ppm potassium monopersulfate triple salt (313 ppm of KHSO5), respectively.

[0054] Procedure:

[0055] In glass vials, 12 ml of each solution was added to 6 ml of the Iron sulfide suspension to reach a final concentration of 1667 ppm potassium monopersulfate triple salt (834 ppm of KHSO5) and 417 ppm potassium monopersulfate triple salt (209 ppm of KHSO5), respectively. The vials were mixed and sealed with a rubber stopper and stored at room temperature for 2 hours. Deionized water was used as a negative control. A second set of vials was prepared by the same procedure, and the second set was incubated at 40°C for 2 hours. After incubation, the vials were cooled to room temperature. All vials were mixed by shaking and visually observed, and the optical density at 450nm w avelength (OD450) was assessed. Higher OD450readings indicated a greater presence of the black iron sulfide contained in the mixture. Tests were run in duplicate.

[0056] As shown in FIG. 1 (room temperature incubation) and FIG. 2 (40°C incubation), the potassium hydrogen peroxymonosulfate dissolved the iron sulfide, and the concentration of potassium monopersulfate triple salt of 1667 ppm (834 ppm of KHSO5) provided a clearer solution based on visual observation.

[0057] The reduction (%) of the OD450reading as compared to the control readings is shown in Table 1 .

[0058] Table 1 . OD450reduction as compared to untreated control (% reduction compared to control)

[0059] Example 2:

[0060] Materials:

[0061] Sulfate reducing bacteria: Desulfovibrio alaskensis ATCC 14563.

[0062] Culture medium 1250: Modified Barr's Medium with 2.5% NaCl (ATCC Medium 1250) amended with 0.01% of ferrous ammonium sulfate hexahydrate.

[0063] Deoxygenated DI w-ater (deionized water moved to an anaerobic chamber without CO2gas after autoclaving and stored for at least two days with cap loosened). Iron sulfide suspension: Desulfovibrio akiskensis ATCC 14563 was grown in Culture medium 1250 at 30°C for 3 days. 25 ml of the culture was centrifuged at 1000g for 5 minutes and the precipitate collected. The precipitate was then resuspended in 50 ml of deoxygenated DI water.

[0064] Potassium hydrogen peroxymonosulfate (KHSO5) was provided in the form of a potassium monopersulfate triple salt (available under the brand name OXONE® and commonly represented by the formula 2KHSO5.KHSO4.K2SO4).

[0065] Procedure:

[0066] In a 96-well plate, 100 pl of i ron sulfide suspension aliquots were mixed with potassium monopersulfate triple salt (OXONE®) solutions (in deoxygenated DI water) and sodium nitrite solutions (in deoxygenated DI water), respectively. After mixing, the plate was read at 450nm wavelength ( OD450). The plate was then incubated at room temperature for 4 hours. OD450was read again after the incubation. The test was run in triplicates. The OD450readings are summarized in Table 2.

[0067] Table 2. OD450readings immediately following treatment and after 4-hour incubation

[0068] As shown in Table 2, potassium hydrogen peroxymonosulfate was more effective at dissolving iron sulfide than sodium nitrite even at significantly lower concentrations.

[0069] After the treatments, the plate was also read at OD620for assessing turbidity. The OD620readings are summarized in Table 3.

[0070] Table 3. The iron sulfide suspensions treated with potassium hydrogen monopersulfate showed reduced turbidity, further indicating that the potassium hydrogen monopersulfate controlled the iron sulfide while reducing or mitigating the formation or production of insoluble elemental sulfur.

[0071] Example 3:

[0072] Materials:

[0073] Sulfate reducing bacteria: Desulfovibrio alaskensis ATCC 14563.

[0074] Culture medium 1250: Modified Barr's Medium with 2.5% NaCl (ATCC Medium 1250) amended with 0.01% of ferrous ammonium sulfate hexahydrate.

[0075] Deoxygenated DI water (deionized water moved to an anaerobic chamber without CO2gas after autoclaving and stored for at least two days with cap loosened).

[0076] Iron sulfide suspension: Desulfovibrio alaskensis ATCC 14563 was grown in Culture medium 1250 at 30°C for 3 days. 60 ml of the culture was centrifuged at 1000g for 5 minutes and the precipitate collected. The precipitate was then resuspended in 180 ml of deoxygenated DI water.

[0077] Potassium hydrogen peroxymonosulfate (KHSO5) was provided in the form of a potassium monopersulfate triple salt (available under the brand name OXONE®and commonly represented by the formula 2KHSO5.KHSO4.K2SO4).

[0078] Procedure:

[0079] To each of three 100 mL glass flasks, 40 mL of the iron sulfide suspension were added and mixed with potassium monopcrsulfatc triple salt (OXONE®) solution, sodium hypochlorite (NaOCl) solution and peracetic acid (PAA) solution (each solution prepared in deoxygenated DI water), respectively. The flasks were stirred by hand to mix and 200 μ L of each mixture (in triplicate) were transferred to each well of a 96-well microtiter plate and read at 450nm wavelength (OD450). The OD450readings are summarized in Table 4.

[0080] Table 4. OD450readings immediately after treatment

[0081] As shown in Table 4, potassium hydrogen peroxymonosulfate showed rapid iron sulfide dissolution activity higher than that of NaOCl and PAA, even at half of the active ingredient concentration compared to NaOCl and PAA. After the treatments, the plate was also read at OD620for assessing turbidity. The OD620readings are summarized in Table 5.

[0082] Table 5.

[0083] The iron sulfide suspensions treated with potassium hydrogen monopersulfate not only showed superior rapid iron sulfide dissolution at half of the active ingredient concentration but also showed reduced turbidity (Table 5), further indicating that the potassium hydrogen monopersulfate controlled the iron sulfide while reducing or mitigating the formation or production of insoluble elemental sulfur.

[0084] Additionally, the mixture in each flask was transferred to a centrifuge tube and centrifuged at 3000g for 10 minutes. After supernatant was removed, 50mL of DI water were added to each tube and pellets which had setled in the tube after centrifugation were resuspended to remove water soluble sulfur-containing compounds such as sulfate. The suspension was centrifuged again at 3000g for 10 minutes and the wash step was repeated once more. The pellets were suspended with 2 mL of Milli-Q water and transferred to a 15ml quartz digestion vial. Material remaining in the tube was rinsed three times with 2mL HNO3each time and transferred to each quartz digestion vial. After digestion in HNO3, the samples were filtered (0.22μm PVDF filter) and analyzed using ICP-MS (inductively coupled plasma mass spectrometry). The results are summarized in Table 6.

[0085] Table 6. Total sulfur detected in washed iron sulfide dissolution samples using ICP-MS analysis

[0086] The results in Table 6 show that, in addition to providing superior rapid iron sulfide dissolution at half of the active ingredient concentration, the potassium hydrogen monopersulfate reduced or mitigated the formation or production of insoluble sulfur materials, including elemental sulfur.

Claims

What is claimed is:

1. A method of controlling iron sulfide associated with a wellbore, downhole formation, reservoir or well, or infrastructure or equipment used in the extraction, production, processing, transportation, storage or disposal of a fluid, the method comprising adding or delivering an effective amount of an alkali metal or alkaline earth metal peroxymonosulfate to a fluid that contacts or flows or is stored within the wellbore, the downhole formation, reservoir or well, or the infrastructure or equipment, and dissolving iron sulfide wdth the fluid comprising the alkali metal or alkaline earth metal peroxymonosulfate.

2. The method of claim 1, wherein the alkali metal or alkaline earth metal peroxymonosulfate is potassium hydrogen peroxy monosulfate (KHSO5).

3. The method of claim 2, wherein the method comprises adding or delivering to the fluid that contacts or flows or is stored within the wellbore, the downhole formation, reservoir or well, or the infrastructure or equipment a potassium monopersulfate triple salt to provide the effective amount of the potassium hydrogen peroxymonosulfate (KHSO5), and wherein the triple salt further comprises KHSO4and K2SO4.

4. The method of claim 3, wherein the potassium monopersulfate triple salt is represented by the formula (KHSO5)x(KHSO4)y(K2SO4)zfor which the sum of mole fractions x, y, and z equals 1 , and x is 0.43-0.64, y is 0.15-0.43, and z is 0.15-0.43.

5. The method of claim 3, wherein the potassium monopersulfate triple salt is represented by the formula 2KHSO5.KHSO4.K2SO4.

6. The method of any preceding claim, wherein the wellbore, the downhole formation, reservoir or well, or the infrastructure or equipment is used for extracting, producing, processing, refining, transporting or storing crude or processed oil or natural gas.

7. The method of any preceding claim, wherein the fluid that contacts or flows or is stored within the wellbore, the downhole formation, reservoir or well, or the infrastructure or equipment comprises at least one of injection water, formation water, produced water, flowback water, waste water, cooling water or source water.

8. The method of any preceding claim, wherein the fluid that contacts or flows or is stored within the wellbore, the downhole formation or reservoir, or the infrastructure or equipment comprises natural gas, a liquid hydrocarbon or a combination thereof.

9. The method of any preceding claim, wherein the iron sulfide to be dissolved is dispersed within the wellbore, the downhole formation, reservoir or well, or the infrastructure or equipment.

10. The method of any preceding claim, wherein the iron sulfide to be dissolved is deposited on a surface of the wellbore or the infrastructure or equipment.11 . The method of any preceding claim, wherein the iron sulfide to be dissolved is deposited on or in a pore space, porous media or mineral surface of the downhole formation, reservoir or well.

12. The method of any preceding claim, wherein the infrastructure or equipment comprises a pipeline, storage vessel, tank, tubing, flow line, injection line, production line, wellhead, pump, scrubber or heat exchanger.

13. The method of any preceding claim, wherein the effective amount provides from about 50 ppm to about 10000 ppm of the alkali metal or alkaline earth metal peroxymonosulfate.

14. The method of any one of claims 2-13, wherein the method comprises adding or delivering to the fluid that contacts or flows or is stored within the wellbore, the downhole formation, reservoir or well, or the infrastructure or equipment a potassium monopersulfate triple salt to provide the effective amount of the potassium hydrogen peroxymonosulfate (KHSO5), and the addition provides from about 100 ppm to about 20000 ppm of the potassium monopersulfate triple salt.

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