Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/60—Compositions for stimulating production by acting on the underground formation
  • C09K8/62—Compositions for forming crevices or fractures
  • C09K8/72—Eroding chemicals, e.g. acids

Definitions

• the invention relates to methods of treating oil or gas wells to enhance flow rates of the oil or gas.
• Petroleum hydrocarbons are generically referred to as “oil” and include both hydrocarbon gases and liquids.
• the proportion of gas to liquids may vary and the commercial production may be predominately gases, or hydrocarbon liquids, or both.
• reservoirs of such hydrocarbons typically occur within porous sedimentary strata containing silica-based minerals (e.g., sandstone, feldspars) and/or carbonate-based minerals (e.g., limestone, dolomite).
• Strata that are largely carbonate will also contain silica-based minerals and vice versa.
• the oil exists in microscopic pores interconnected by networks of microscopic flow channels.
• impeded flow can arise from “damage” to the formation.
• One source of such damage sometimes occurs as a consequence of the well drilling, completion, and production operations.
• This damage takes the form of mineral particles from the drilling and completion fluids that have coated the face of the wellbore or have invaded the near-wellbore strata, and mineral particles originally from the oil-bearing strata that were mobilized during the drilling, completion and production operations.
• the damage from these particles may occur at or near the wellbore, but may also occur anywhere along the flow path of the oil and water that migrate through the formation.
• matrix acidizing involves injecting an acid or acid-based fluid, often along with other chemicals, through the wellbore to a targeted strata such that the acid can (a.) react with and dissolve particles and scale in the wellbore and near-wellbore strata or (b.) react with and dissolve small portions of the strata to create alternate flow paths around the damaged strata, thereby enhancing the permeability of the rock.
• Hydrochloric and/or hydrofluoric acid are commonly used for this purpose.
• the invention provides a method of treating an oil well that includes injecting into the well a composition comprising a latent acid comprising a sulfonyl moiety.
• the latent acid is capable of providing an active acid after injection into an oil well.
• latent acid means a compound that does not itself have substantial acidic character, but which is capable of being converted to a mineral acid or a strong organic acid (“active acid”) that is able to dissolve carbonates, silicates, sulfides, and/or other acid-soluble materials in an oil well.
• active acid a strong organic acid
• dissolve includes reactive dissolution as well as simple dissolution.
• the latent acids of this invention include all compounds containing a sulfonyl moiety (—SO 2 —) capable of providing an active acid after injection into an oil well. Three exemplary classes of such compound are shown below, but the invention is not limited to these.
• One class of latent acids of this invention consists of compounds having structures according to formula (I).
• R 1 is selected from C 1 -C 30 hydrocarbyl moieties optionally appended to an oligomeric or polymeric chain or substituted with functional groups containing halogen, oxygen, sulfur, selenium, silicon, tin, lead, nitrogen, phosphorous, antimony, bismuth, aluminum, boron, or metals selected from Groups IA-IIA and IB-VIIIB of the periodic table;
• X is a halogen (F, Cl, Br, I) or ZCR 2 R 3 R 4 ;
• Y and Z are independently O, S, Se, or NR 6 , and Y may also be a direct bond; and
• R 2 , R 3 , R 4 and R 5 are independently hydrogen or as defined for R 1 .
• Hydrocarbyl moieties for any of R 1 -R 5 are typically any branched or linear alkyl group, aralkyl group, alkaryl group, or cyclic or alicyclic group.
• Suitable nonlimiting examples of groups suitable for use as any of R 1 -R 5 are include straight-chain or branched-chain alkyl groups containing from one to six carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, tert-butyl, isobutyl, n-pentyl, 2-pentyl, tert-pentyl, isopentyl, neopentyl, 2-methylpentyl, n-hexyl, and isohexyl; straight-chain or branched-chain alkyl groups containing from seven to twenty carbon atoms, such as heptyl, 2-ethylhexyl, octyl, nonyl, 3,5-dimethyloctyl, 3,7-dimethyloctyl, decyl, undecyl, dodecyl, tridecyl,
• any two or more of R 1 , R 2 , R 3 , R 4 and R 5 may optionally be interconnected to form one or more cyclic structures.
• substituent groups are incorporated in any of R 1 , R 2 , R 3 , R 4 and R 5 , the groups will contain halogen, oxygen, sulfur, nitrogen, silicon, or phosphorus.
• the preparation of latent acids of formula (I) may be effected by any method known in the chemical art. For example, suitable methods are reviewed in Chapter 10 of The Chemistry of Sulfonic Acids, Esters, and their Derivatives; Patai, S, Rappoport, Z., Eds.; pp. 351-399, John Wiley and Sons: New York, 1991.
• a second class of latent acids consists of compounds according to formula (II)
• a third class of latent acids consists of compounds according to formula (III)
• Any of R 1 -R 4 may optionally bear an additional oxygen or nitrogen substituent that bonds to another metal atom, so that dimeric, trimeric, oligomeric, and polymeric structures containing multiple metal atoms may also be made for use according to the invention.
• Nonlimiting examples include structures according to formula (IIIa),
• Latent acids may react in the production zone of the well to form active acidic species, for example sulfonic acids, mineral acids, etc. These in turn react with minerals to form water-soluble salts, thus removing solid minerals to enhance to enhance the porosity of the rock formation, removing debris from the production zone or wellbore, or removing acid-labile materials purposely placed in the well to perform some particular function.
• active acidic species for example sulfonic acids, mineral acids, etc.
• the latency characteristic of compounds according to formula (I) refers to their potential for delayed reactivity, thus allowing greater radial diffusion through the rock formation in the production zone of the well before formation of the acidic species and their subsequent reaction with carbonate, silicate, sulfide, or other minerals, which allows removal of the dissolved minerals from the formation and the wellbore.
• Exemplary water-soluble salts produced in this way include, as nonlimiting examples, calcium, magnesium, barium, and iron salts derived from methanesulfonic acid and hydrochloric acid, as well as fluorosilicates derived from hydrofluoric acid and siliceous minerals.
• the methanesulfonic (and in some cases, hydrochloric) acid generated by certain embodiments of this invention generally form highly soluble calcium and magnesium salts.
• hexafluorosilicate salts of sodium, magnesium, and iron are also soluble. These may be formed, for example, when the latent acid is a sulfonyl fluoride that contacts silica deposits containing any of these metals.
• Latent acids according to formula (I) typically have relatively low solubility in water or brine media, and this is believed to contribute to their delayed reaction with water to form active acids.
• Hydrolysis of sulfonyl halides is strongly temperature dependent, occurring at very slow rates at ambient temperatures, but more rapidly at elevated temperatures such as may typically be found in the production zone of an oil well.
• sulfonyl halide latent acids useful in the practice of this invention are typically of relatively low solubility in water at neutral or acidic pH, and this also tends to slow the hydrolysis of the sulfonyl halide according to Eqn. 1a.
• the pH of the production zone is typically high due to the presence of carbonates and/or other basic minerals, and this may accelerate the formation of active acids in those areas that contain such minerals.
• these dependencies of hydrolysis rate (i.e., Eqn. 1a) on the temperature and the pH of the medium may both contribute to the latency of acid activity for compounds of formula (I).
• the sulfonic (and hydrohalic, in some cases) acid will then diffuse through the largely aqueous medium until it contacts solid carbonate-containing minerals, whereupon the neutralization reactions (Eqns. 1b and 1 c) may occur to form the water-soluble salt products.
• the degree of conversion of calcium carbonate to HCO 3 ⁇ or CO 2 species shown in Eqns. 1b and 1c depends on the pH of the aqueous medium, which in turn is governed by the relative rates of hydrolysis of the sulfonyl halide as compared to the dissolution and subsequent reaction of the carbonate species, as well as on the presence of other alkaline species other than carbonate that may be present.
• Similar chemistry may operate for acid halides of the formula R 1 YSO 2 X.
• the R 1 YSO 3 ⁇ species may undergo further hydrolysis and neutralizations to form R 1 YH and hydrated forms of calcium sulfate.
• one of the hydrolysis products is HF, which is strongly reactive with silica to form H 2 SiF 6 , which can subsequently react with carbonates or other basic minerals to form water-soluble hexafluorosilicate salts (not shown).
• the initial hydrolysis reaction is also strongly temperature dependent. Moreover, the solubilities of these latent acids in aqueous media decrease markedly with increasing size of the R 1 , R 2 , R 3 and R 4 groups, thereby increasing their latency characteristics.
• the initial hydrolysis reaction can be represented as follows, with resulting sulfonic acid R 1 SO 3 H further reacting with the calcium carbonate as previously discussed.
• the latent acids are esters of the formulas R 1 SO 2 ZCR 2 R 3 R 4 and R 1 YSO 2 ZCR 2 R 3 R 4
• incorporation of nucleophilic agents into the formulation may in some embodiments be used to increase the rate of conversion of the latent acid to an active acid.
• the initial reaction with the nucleophile (Nu—H) can be represented as follows, with the resulting sulfonic acid R 1 SO 3 H further reacting with the calcium carbonate as previously discussed.
• the latent acids In order to modify the reactivity and improve the handling characteristics of the latent acids, it may be desirable to combine them in a formulation with other materials such as catalysts, solvents, water, aqueous acids or salts, emulsifying agents, corrosion inhibitors, viscosity modifiers, etc.
• Such additives may, for example, alter reactivity, provide an additional benefit such as corrosion protection, improved handling characteristics, decreased vapor pressure of undesirable components, or produce or modify the additive on the surface prior to injection into the well, in the well, or in the rock formation.
• any number of organic solvents may also be added.
• suitable solvents for some or all of the above latent acids include diesel fuel, toluene, xylenes, halogenated solvents, alcohols, ketones, and esters.
• the latent acids may also be prepared in the form of an emulsion or suspension incorporating water, aqueous acids or salts, emulsifying agents, and optional solvents.
• Hydrochloric acid, hydrofluoric acid, sulfamic acid, acetic acid, and formic acid are examples of suitable aqueous acids.
• the latent acid may also be combined with an immiscible liquid with a density substantially lower than that of the latent acid, such that the immiscible liquid serves as a barrier to reduce the vapor pressure of the latent acid.
• barrier materials may include low-flammability hydrocarbons (e.g., mineral oils), and silicone fluids.
• the latent acids may be combined with solid organic or inorganic adsorbants, so as to allow the controlled release of the latent acids when these combined materials are suspended in water or other media for delivery to the targeted strata via the wellbore.
• Suitable adsorbants include clays, aluminas, silicas, polyacrylic acids/amides/esters, polymethacrylic acids/amides/esters, polyamides, polyesters, polyethers, polyvinyl alcohol, etc., possessing suitable adsorptive and release properties for the particular latent acid being employed.
• the latent acid may be formulated within an encapsulating material such as wax.
• Catalysts may also be added to modify the reactivity of the latent acid.
• Nonlimiting examples may include compounds with amine, amine salt, amide, thiol, quaternary ammonium, quaternary phosphonium, sulfonium chemical functionality.
• Examples of the quaternary ammonium and phosphonium catalysts include tetrabutylammonium, methyl tributylammonium (e.g., Cognis ALIQUAT-175), methyl tricaprylylammonium (e.g., Cognis ALIQUAT-336), N-methyl-N-butyl imidazolium, hexaethylguanidinium, or tetrabutylphosphonium (e.g., Cytec CYPOS-442) salts.
• tetrabutylammonium e.g., Cognis ALIQUAT-175
• methyl tricaprylylammonium e.g., Cognis ALIQUAT-336
• N-methyl-N-butyl imidazolium e.g., hexaethylguanidinium
• tetrabutylphosphonium e.g., Cytec CYPOS-442
• amine catalysts include tertiary or aromatic amines such as triethylamine, ethyl diisopropyl amine, pyridine, quinoline, and lutidine, or their salt forms.
• amides include formamide, acetamide, pyrrolidinone, polyvinylacetamide, urea, and N-alkylated analogs thereof.
• thiol catalysts include alkyl or aromatic thiols, thiophenol, thioglycolic acid, cysteine, mercaptoethanesulfonic acid or its salts, and mercaptopropanesulfonic acid or its salts.
• Other catalysts include nonionic or anionic surfactants.
• Nucleophilic agents may optionally be incorporated into these formulations in super- or sub-stoichiometric amounts to modify the reactivity of the latent acids, particularly when the latent acids is a sulfonate ester of the formula R 1 SO 2 OCR 2 R 3 R 4 or R 1 YSO 2 OCR 2 R 3 R 4 as defined above.
• the nucleophile may react with the —CR 2 R 3 R 4 group to liberate the R 1 SO 3 ⁇ or R 1 YSO 3 ⁇ groups in salt or acid form for reaction with carbonate, silicate, sulfide, or other minerals.
• nucleophilic agents include, but are not limited to, amines, thiols, alcohols, and combination thereof, such as triethylamine, triethanolamine, diethylamine, diethanolamine, dibutylamine, diamylamine, pyridine, quinolines, lutidine, C 1 -C 30 alkanethiols, dithiols or polythiols, n-dodecanethiol, t-dodecanethiol, C 1 -C 30 alkanols, diol, polyols, methanol, isopropanol, ethylene glycol, diethyleneglycol, triethylene glycol, ethylene glycol monoethers, 2-ethylhexanol, octanol, fatty alcohols, phenol, and cresols.
• amines, thiols, alcohols, and combination thereof such as triethylamine, triethanolamine, diethylamine, di
• thiols or amines will be used.
• An extension of the above involves the use of sulfite as the nucleophile, wherein the resulting products is two sulfonic salts.
• An example is the reaction of sodium sulfite with methyl methanesulfonate as follows.
• Another embodiment of the invention uses a formulation wherein a first latent acid reacts with another ingredient to form a second latent acid in the well or the production zone.
• One exemplary embodiment uses a formulation comprising a sulfonyl chloride (the first latent acid), an alcohol and optionally a catalyst and/or solvent. The alcohol reacts with the sulfonyl chloride to produce a sulfonate ester (the second latent acid) and hydrochloric acid (an active acid).
• Another embodiment uses a formulation that comprises a latent acid that can be oxidized in the wellbore to a sulfonic acid.
• a thiolsulfonate may be formulated with an oxidizing agent so that upon contact with high temperature or a catalyst in the well, a sulfonic acid is produced.
• suitable oxidizers include hydrogen peroxide, inorganic peroxides, organic peroxides or hydroperoxides, nitric acid, halogens, and hypohalite salts.
• certain materials when used in combination with the latent acids of formula (I), may have a substantial effect on certain important performance properties of the latent acid.
• materials that might tend to form insoluble products by reaction with the latent acid (or active acids derived from it) may or may not be undesirable in a given situation, and therefore some embodiments of the invention preclude the addition of such compounds in amounts that produce significant quantities of insoluble products.
• Nonlimiting examples of substances that may produce significant quantities of insoluble products include soluble aluminum compounds, including but not limited to alkali metal aluminates, and soluble chromium compounds, including but not limited to CrCl 3 . These compounds tend to form insoluble hydroxides, oxides, and/or other precipitates when contacted with latent acids and/or the active acids derived from them.
• the process of this invention involves injection of the latent acids, optionally within a formulation also comprising catalysts, solvents, water, aqueous acids or salts, emulsifying agents, encapsulating agents, vapor-pressure reducing materials, corrosion inhibitors, viscosity modifiers, and/or other ingredients, into the wellbore and production zone of the well.
• a formulation also comprising catalysts, solvents, water, aqueous acids or salts, emulsifying agents, encapsulating agents, vapor-pressure reducing materials, corrosion inhibitors, viscosity modifiers, and/or other ingredients
• the composition is injected into strata in the well having a temperature from 20 to 250° C., typically from 50 to 150° C.
• the strata contain predominately silica-containing rock, and in such cases it may be use for the latent acid to comprise R 1 SO 2 F or R 1 YSO 2 F.
• the latent acid may comprise R 1 SO 2 Cl or R 1 YSO 2 Cl, and it may be accompanied by sodium fluoride, potassium fluoride, or barium fluoride so that HF is ultimately formed in the strata.
• HCl and/or HF themselves may also be added to these or any other formulation containing a latent acid.
• Methanesulfonyl Chloride as Latent Acid for Reaction with Calcium Carbonate in Water and in Brine in the Absence of Organic Solvents
• the following workup was employed: The tube was vented of formed CO 2 gas and the contents transferred to a syringe fitted with a filter. The syringe piston was then reattached and the liquid contents were forced through the filter and collected. The mixed aqueous and organic filtrates were allowed to separate and the organic phase removed by pipette. The solids in the filter were then washed with fresh 1,2-dichloroethane (2.00 g) to remove any absorbed organics and allowed to combine with the original aqueous phase. The combined aqueous phase and organic washings were then shaken to extract any residual sulfonyl chloride in the aqueous phase, and the organic washings combined with the previously organic phase.
• the combined organic phases for each tube were analyzed by gas chromatography to determine the amount of unreacted sulfonyl chloride.
• Methanesulfonic Acid (70%, 0.288 g, 2.10 mmol) was combined with brine (0.66 g NaCl in 2.00 g water). Calcium carbonate (0.50 g, 5.0 mmol) was then added and the mixture heated at 80° C. for 30 minutes. The undissolved solids were then removed by filtration. The experiment was repeated using an equimolar amount of hydrochloric acid (37%, 0.206 g) in place of the methanesulfonic acid. Examination of both aqueous filtrates by inductively-coupled plasma spectroscopy revealed each to contain ca. 16000 ppm (1.6%) Ca 2+ content.
• n-octyl methanesulfonate 0.44 g
• 2-ethylhexyl methanesulfonate EHMS
• brine 0.66 g NaCl in 2.00 g water
• calcium carbonate 0.20 g
• MTBAC methyl tributylammonium chloride
• MTCAC methyl tricaprylammonium chloride
• nonionic surfactants and anionic surfactants as catalysts to modify the hydrolysis rates of octyl methanesulfonate was compared with that for a quaternary alkylammonium salt (methyl tributylammonium chloride, MTBAC).
• MTBAC methyl tributylammonium chloride
• the tested materials included PLURONIC non-ionic surfactants (products of BASF) and ARISTONATE anionic surfactants (products of Pilot Chemical Co.)
• n-octyl methanesulfonate 0.44 g was contacted with calcium carbonate (0.20 g) in brine (0.66 g NaCl and 2.00 g water) at 80° C. for 120 minutes in the presence of the prospective catalysts (0.44 g). The results are tabulated below.
• the quaternary alkylammonium catalyst provided 8.6-15.2 times the hydrolysis rate as compared to the non-ionic and anionic surfactants.

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• 2006
  • 2006-07-12 WO PCT/US2006/026967 patent/WO2007018922A2/en active Application Filing
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