# US 2023/0056620 A1 · Single-fluid mixed scale dissolution > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0056620 A1 - Document ID: US20230056620A1 - Status: Published application - Kind: A1 - Application number: 17/403,659 - Filed: 2021-08-16 - Published: 2023-02-23 - Earliest claimed: 2021-08-16 - Assignees: Halliburton Energy Services, Inc. - Applicants: Halliburton Energy Services, Inc. - Inventors: Enrique Antonio Reyes; Sarai Santos; Kristina Henkel Holan; Antonio Recio, III - Web page: https://patentgrep.com/patent/US20230056620A1 ## CPC - C09K 8/528: inorganic depositions, e.g. sulfates or carbonates - E21B 37/06: using chemical means for preventing or limiting {, e.g. eliminating,} the deposition of paraffins or like substances - C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract Methods and treatment fluids for removing mixed scale. A treatment fluid is introduced into a wellbore comprising a mixed scale of interspersed calcium carbonate and calcium sulfate. The treatment fluid comprises: phosphonomethyliminodiacetic acid, glycine-N,N-bis(methylene phosphonic acid), or a combination thereof; and an aqueous base fluid. The treatment fluid has a pH in a range between about 6 to about 8. The method further comprises contacting the mixed scale with the treatment fluid. ## Claims ### Claim 1 A method of removing mixed scale, the method comprising: introducing a treatment fluid into a wellbore comprising a mixed scale of interspersed calcium carbonate and calcium sulfate, wherein the treatment fluid comprises: phosphonomethyliminodiacetic acid, glycine-N,N-bis(methylene phosphonic acid), or a combination thereof, and an aqueous base fluid; wherein the treatment fluid has a pH in a range between about 6 to about 8; and contacting the mixed scale with the treatment fluid. ### Claim 2 (depends on 1) The method of claim 1, wherein the treatment fluid is a single treatment fluid. ### Claim 3 (depends on 1) The method of claim 1, wherein 60% of the mixed scale is dissolved within a six hour period after the contacting of the mixed scale with the treatment fluid without the introduction of an additional treatment fluid. ### Claim 4 (depends on 1) The method of claim 1, wherein the mixed scale is not treated with xylene or toluene prior to the introducing the treatment fluid into the wellbore. ### Claim 5 (depends on 1) The method of claim 1, wherein the phosphonomethyliminodiacetic acid or glycine-N,N-bis(methylene phosphonic acid) is present in a concentration in a range between about 1% (w/v) to about 50% (w/v). ### Claim 6 (depends on 1) The method of claim 1, wherein the treatment fluid further comprises a chelating agent selected from the group consisting of hydroxyethylenediaminetetraacetic acid, N-(2-hydroxethyl)ethylenediaminetriacetic acid, hydroxyethyliminodiacetic acid, methylglycine diacetic acid, gluconic acid diacetic acid, ethylenediaminedisuccinic acid, beta-alaninediacetic acid, diethylenetriaminepentaacetic acid, cyclohexylenediaminetetraacetic acid, nitrilotriacetic acid, diphenylaminesulfonic acid, polyaminoacids, polyaspartic acid, polyitaconic acid, polysuccinic acid, polylactic acid, polyglycolic acid, and any combination thereof. ### Claim 7 (depends on 1) The method of claim 1, wherein the treatment fluid further comprises a surfactant selected from the group consisting of fatty acid alkoxylates, amine oxides, alkanolamides, alkoxylated alcohols, alkylamine alkoxylates, alkyl glycosides, and any combination thereof. ### Claim 8 (depends on 1) The method of claim 1, wherein the treatment fluid does not comprise carbonate or bicarbonate. ### Claim 9 (depends on 1) The method of claim 1, wherein the treatment fluid does not comprise a carboxylate-containing alkanol, a carboxylated alkyl halide, or a multicarboxylic acid. ### Claim 10 (depends on 1) The method of claim 1, wherein the ratio of calcium carbonate to calcium sulfate in the mixed scale is in a range between about 90/10 to about 25/75. ### Claim 11 (depends on 1) The method of claim 1, wherein the pH of the treatment fluid is in a range between about 6.5 to about 7.5. ### Claim 12 A treatment fluid for treating mixed scale, the treatment fluid comprising: phosphonomethyliminodiacetic acid, glycine-N,N-bis(methylene phosphonic acid), or a combination thereof, and an aqueous base fluid; wherein the treatment fluid has a pH in a range between about 6 to about 8; wherein the treatment fluid does not comprise a carboxylate-containing alkanol, a carboxylated alkyl halide, or a multicarboxylic acid; and wherein the treatment fluid does not comprise carbonate or bicarbonate. ### Claim 13 (depends on 12) The treatment fluid of claim 12, wherein the phosphonomethyliminodiacetic acid or glycine-N,N-bis(methylene phosphonic acid) is present in a concentration in a range between about 1% (w/v) to about 50% (w/v). ### Claim 14 (depends on 12) The treatment fluid of claim 12, wherein the treatment fluid further comprises a chelating agent selected from the group consisting of hydroxyethylenediaminetetraacetic acid, N-(2-hydroxethyl)ethylenediaminetriacetic acid, hydroxyethyliminodiacetic acid, methylglycine diacetic acid, gluconic acid diacetic acid, ethylenediaminedisuccinic acid, beta-alaninediacetic acid, diethylenetriaminepentaacetic acid, cyclohexylenediaminetetraacetic acid, nitrilotriacetic acid, diphenylaminesulfonic acid, polyaminoacids, polyaspartic acid, polyitaconic acid, polysuccinic acid, polylactic acid, polyglycolic acid, and any combination thereof. ### Claim 15 (depends on 14) The treatment fluid of claim 14, wherein the chelating agent is present in a concentration in a range between about 1% (w/v) to about 40% (w/v). ### Claim 16 (depends on 12) The treatment fluid of claim 12, wherein the treatment fluid further comprises a surfactant selected from the group consisting of fatty acid alkoxylates, amine oxides, alkanolamides, alkoxylated alcohols, alkylamine alkoxylates, alkyl glycosides, and any combination thereof. ### Claim 17 A system for removing mixed scale from a wellbore, the system comprising: a treatment fluid comprising: phosphonomethyliminodiacetic acid, glycine-N,N-bis(methylene phosphonic acid), or a combination thereof, and an aqueous base fluid; wherein the treatment fluid has a pH in a range between about 6 to about 8; wherein the treatment fluid does not comprise a carboxylate-containing alkanol, a carboxylated alkyl halide, or a multicarboxylic acid; and wherein the treatment fluid does not comprise carbonate or bicarbonate; mixing equipment configured to mix the phosphonomethyliminodiacetic acid or the glycine-N,N-bis(methylene phosphonic acid) and the aqueous base fluid to provide the treatment fluid; and pumping equipment configured to pump the treatment fluid into the wellbore to a location comprising the mixed scale. ### Claim 18 (depends on 17) The system of claim 17, wherein the pumping equipment is configured to not circulate the treatment fluid during a reaction time in which the treatment fluid is contacting the mixed scale. ### Claim 19 (depends on 17) The system of claim 17, wherein the treatment fluid further comprises a chelating agent selected from the group consisting of hydroxyethylenediaminetetraacetic acid, N-(2-hydroxethyl)ethylenediaminetriacetic acid, hydroxyethyliminodiacetic acid, methylglycine diacetic acid, gluconic acid diacetic acid, ethylenediaminedisuccinic acid, beta-alaninediacetic acid, diethylenetriaminepentaacetic acid, cyclohexylenediaminetetraacetic acid, nitrilotriacetic acid, diphenylaminesulfonic acid, polyaminoacids, polyaspartic acid, polyitaconic acid, polysuccinic acid, polylactic acid, polyglycolic acid, and any combination thereof. ### Claim 20 (depends on 17) The system of claim 17, wherein the treatment fluid further comprises a surfactant selected from the group consisting of fatty acid alkoxylates, amine oxides, alkanolamides, alkoxylated alcohols, alkylamine alkoxylates, alkyl glycosides, and any combination thereof.