# US 2014/0196904 A1 · Methods of Controlled Release pH Adjustment for Oilwell Stimulation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0196904 A1 - Document ID: US20140196904A1 - Status: Published application - Kind: A1 - Application number: 13/741,626 - Filed: 2013-01-15 - Published: 2014-07-17 - Earliest claimed: 2013-01-15 - Assignees: Halliburton Energy Services, Inc. - Applicants: Halliburton Energy Services, Inc. - Inventors: Lucas K. Fontenelle; Melissa C. Weston - Web page: https://patentgrep.com/patent/US20140196904A1 ## CPC - C09K 8/685: {containing cross-linking agents} - E21B 43/26: by forming crevices or fractures - 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 A method for treating subterranean formations by the use of delayed release pH control agents in subterranean formations during fracturing operations includes providing a fracturing fluid comprising a base fluid, a viscosifying agent, a pH sensitive crosslinking agent, and a delayed release pH-adjusting material. The delayed release pH-adjusting material includes a pH-adjusting agent and a binder. The fracturing fluid is introduced into a subterranean formation, and the pH of the fracturing fluid is changed through at least partial degradation or disassociation of the delayed release pH-adjusting material, thereby allowing the viscosifying agent to be crosslinked through activation of the pH sensitive crosslinking agent. ## Claims ### Claim 1 A method comprising: providing a fracturing fluid comprising: a base fluid, a viscosifying agent, a pH sensitive crosslinking agent, and a delayed release pH-adjusting material, the delayed release pH-adjusting material comprising a pH-adjusting agent and a binder; placing the fracturing fluid into a subterranean formation; changing the pH of at least a portion of the fracturing fluid through at least partial degradation or disassociation of the delayed release pH-adjusting material; and allowing at least a portion of the viscosifying agent to be crosslinked through activation of the pH sensitive crosslinking agent by the change in pH. ### Claim 2 (depends on 1) The method of claim 1, wherein the delayed release pH-adjusting material further comprises an outer coating. ### Claim 3 (depends on 2) The method of claim 2, wherein the outer coating is comprised of a water-insoluble material and the outer coating has a melting point of about 100° F. to about 500° F. ### Claim 4 (depends on 2) The method of claim 2, wherein the outer coating comprises at least one selected from the group consisting of: a polysaccharide; dextran, starch, cellulose, chitin, lipid, latex, wax, chitosan, protein, aliphatic polyester, poly(lactide), poly(glycolide), poly(ε-caprolactone), poly(hydroxybutyrate), poly(anhydride), aliphatic polycarbonate, orthoester, poly(orthoester), poly(amino acid), poly(ethylene oxide) and polyphosphazene, any derivative thereof, any copolymer or blend thereof, and any combination thereof. ### Claim 5 (depends on 2) The method of claim 2, wherein the outer coating is configured to delay the degradation of the delayed release pH-adjusting material until the delayed release pH-adjusting material is in the portion of the subterranean formation to be fractured. ### Claim 6 (depends on 1) The method of claim 1, wherein the pH-adjusting agent is a base. ### Claim 7 (depends on 6) The method of claim 6, wherein the base comprises at least one selected from the group consisting of: a hydroxide, sodium hydroxide, ammonium hydroxide, potassium hydroxide, magnesium hydroxide, a metal alkali salt, an organic base, a hydroxide of an organic base, a methyl amine, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, any derivative thereof, and any combination thereof. ### Claim 8 (depends on 1) The method of claim 1, wherein the binder comprises at least one selected from the group consisting of: silica gel, aluminosilicate, chitosan, starch, sugar, and cellulose, derivatives thereof, and combinations thereof. ### Claim 9 (depends on 1) The method of claim 1, wherein the viscosifying agent comprises at least one selected from the group consisting of: cellulose, modified cellulose, cellulose derivative, methylcellulose, hydroxyethyl cellulose, carboxyethylcellulose, carboxymethylcellulose, carboxymethylhydroxyethylcellulose, polysaccharide, guar gum, hydroxyethyl guar, hydroxypropyl guar, carboxymethyl guar, carboxymethylhydroxyethyl guar, carboxymethylhydroxypropyl guar, locust bean gum, gum ghatti, gum karaya, tamarind gum, tragacanth gum, xanthan, scleroglucan, succinoglycan, diutan, biopolymers, and/or derivatives thereof that contain one or more of these monosaccharide units: galactose, mannose, glucoside, glucose, xylose, arabinose, fructose, glucuronic acid, or pyranosyl sulfate, any derivative thereof, and any copolymer, combination or blend thereof. ### Claim 10 (depends on 9) The method of claim 9, wherein the viscosifying agent comprises guar, and any derivative thereof. ### Claim 11 (depends on 1) The method of claim 1, wherein the delayed release pH-adjusting material has an average particle diameter of about 0.1 mm to 5 mm. ### Claim 12 (depends on 1) The method of claim 1, wherein the fracturing fluid further comprises proppant particulates. ### Claim 13 (depends on 1) The method of claim 1, wherein the base fluid comprises at least one selected from the group consisting of: fresh water, municipal water, wastewater, saltwater, seawater, brine, produced water, and flowback water, any derivative thereof, and any combination thereof. ### Claim 14 (depends on 12) The method of claim 12, wherein the proppant comprises at least one selected from the group consisting of: sand, bauxite, ceramic material, glass material, polymer material, polytetrafluoroethylene material, nut shell piece, seed shell piece, fruit pit piece, cured resinous particulate, wood, and composite particulate, any derivative thereof, and any combination thereof. ### Claim 15 A method comprising: providing a fracturing fluid comprising: a base fluid, a viscosifying agent, a alkali pH sensitive crosslinking agent, and a delayed release pH-adjusting material, the delayed release pH-adjusting material comprising a basic pH-adjusting agent and a binder; placing the fracturing fluid into a subterranean formation; raising the pH of the fracturing fluid through at least partial degradation of the delayed release pH-adjusting material, and allowing the viscosifying agent to be crosslinked downhole through activation of the pH sensitive crosslinking agent through the raising of the pH. ### Claim 16 (depends on 15) The method of claim 15, wherein the basic pH-adjusting agent comprises at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, magnesium hydroxide, and a metal alkali salt , any derivative thereof, and combination thereof. ### Claim 17 (depends on 15) The method of claim 15, wherein the alkali pH sensitive crosslinking agent comprises at least one selected from the group consisting of aluminum, antimony, chromium, zirconium, magnesium and titanium, any derivative thereof, and combination thereof. ### Claim 18 (depends on 15) The method of claim 15, wherein the delayed release pH-adjusting material further comprises an outer coating. ### Claim 19 (depends on 18) The method of claim 18, wherein the outer coating is comprised of a water-insoluble material and the outer coating has a melting point of about 100° F. to about 500° F. ### Claim 20 (depends on 18) The method of claim 18, wherein the outer coating comprises at least one selected from the group consisting of: a polysaccharide; dextran, starch, cellulose, chitin, lipid, latex, wax, chitosan, protein, aliphatic polyester, poly(lactide), poly(glycolide), poly(ε-caprolactone), poly(hydroxybutyrate), poly(anhydride), aliphatic polycarbonate, orthoester, poly(orthoester), poly(amino acid), poly(ethylene oxide) and polyphosphazene, any derivative thereof, any copolymer or blend thereof, and any combination thereof.