# US 11,078,398 B2 · Drilling fluids that include water-insoluble acid catalyst precursors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,078,398 B2 - Document ID: US11078398B2 - Status: Granted - Kind: B2 - Application number: 16/449,996 - Filed: 2019-06-24 - Published: 2020-12-24 - Granted: 2021-08-03 - Earliest claimed: 2019-06-24 - Assignees: Saudi Arabian Oil Company - Applicants: Saudi Arabian Oil Company - Inventors: Vikrant Wagle; Abdullah Al-Yami; Abdulaziz Alhehal - Web page: https://patentgrep.com/patent/US11078398B2 ## CPC - C09K 8/24: Polymers - C09K 8/508: macromolecular compounds {(C09K8/512 takes precedence)} - C04B 26/12: Condensation polymers of aldehydes or ketones - C04B 26/125: {Melamine-formaldehyde condensation polymers} - C04B 26/28: Polysaccharides or derivatives thereof - C04B 28/02: containing hydraulic cements other than calcium sulfates - C09K 8/035: Organic additives - C09K 8/34: Organic liquids - C09K 8/502: Oil-based compositions - C09K 8/5086: {obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds} - C09K 8/512: containing cross-linking agents - E21B 21/003: {Means for stopping loss of drilling fluid (plastering the borehole wall E21B33/138)} - E21B 33/138: Plastering the borehole wall; Injecting into the formation - C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE - C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract In accordance with one or more embodiments of the present disclosure, a drilling fluid may include a base fluid and one or more formaldehyde-based resins. The drilling fluid may further comprise one or more water-insoluble acid catalyst precursors or the reaction products of such water-insoluble acid catalyst precursors. The present disclosure also describes sealed subterranean petroleum formations that include such drilling fluids and methods for sealing subterranean wellbores by utilizing such drilling fluids. ## Claims ### Claim 1 A drilling fluid comprising: a base fluid comprising an aqueous solution; a formaldehyde-based resin, where the weight ratio of the formaldehyde-based resin to the base fluid is from 1:100 to 50:100; a water-insoluble acid catalyst precursor, where the weight ratio of the sum of the water-insoluble acid catalyst precursor to the total drilling fluid is from 0.5:100 to 20:100; where the drilling fluid transitions from a liquid state to a gelled state when a pH of the drilling fluid is less than 6. ### Claim 2 (depends on 1) The drilling fluid of claim 1, where the formaldehyde-based resin comprises melamine-formaldehyde resin, urea-formaldehyde resin, phenol-formaldehyde resin, or combinations of these. ### Claim 3 (depends on 1) The drilling fluid of claim 1, where the water-insoluble acid catalyst precursor comprises a water-insoluble hydrolysable polyester. ### Claim 4 (depends on 1) The drilling fluid of claim 1, where the water-insoluble acid catalyst precursor comprises polylactide, polyhdroxylakanoates, polyglycolide, polylactoglycolide, polycaprolactone, or combinations of these. ### Claim 5 (depends on 1) The drilling fluid of claim 1, where the drilling fluid comprises one or more weighting agents, where the weight ratio of the one or more weighting agents to the base fluid is from 10:100 to 300:100. ### Claim 6 (depends on 1) The drilling fluid of claim 1, where the drilling fluid has a density of from 50 pounds per cubic foot to 160 pounds per cubic foot. ### Claim 7 (depends on 1) The drilling fluid of claim 1, where the drilling fluid is in a gelled state such that the apparent viscosity at 300 rpm and 25° C. of the drilling fluid is greater than or equal to 50,000 centiPoise. ### Claim 8 (depends on 1) The drilling fluid of claim 1, where the drilling fluid comprises polyvinyl alcohol or vinyl alcohol copolymers and the weight ratio of the polyvinyl alcohol or vinyl alcohol copolymers to the total weight of the drilling fluid is less than or equal to 1.5:100. ### Claim 9 (depends on 1) The drilling fluid of claim 1, where the drilling fluid comprises latex and the weight ratio of the latex to the total weight of the drilling fluid is less than or equal to 10:100. ### Claim 10 (depends on 1) The drilling fluid of claim 1, where the drilling fluid further comprises a basic additive comprising sodium hydroxide, potassium hydroxide, or both, and where the weight ratio of the basic additive to the base fluid is from 0.001:100 to 5:100. ### Claim 11 A sealed subterranean petroleum formation comprising: a subterranean wellbore positioned adjacent a subterranean petroleum formation; and a drilling fluid positioned in the subterranean wellbore, the drilling fluid comprising: a base fluid comprising an aqueous solution; a formaldehyde-based resin, where the weight ratio of the formaldehyde-based resin to the base fluid is from 1:100 to 50:100; a water-insoluble acid catalyst precursor, the weight ratio of the sum of the water-insoluble acid catalyst precursor to the total drilling fluid is from 0.5:100 to 20:100; where the drilling fluid transitions from a liquid state to a gelled state when a pH of the drilling fluid is less than 6. ### Claim 12 (depends on 11) The sealed subterranean petroleum formation of claim 11, where the drilling fluid is in a gelled state such the apparent viscosity at 300 rpm and 25° C. of the drilling fluid is greater than or equal to 50,000 centiPoise. ### Claim 13 (depends on 11) The sealed subterranean petroleum formation of claim 11, where the drilling fluid comprises latex and the weight ratio of the latex to the total weight of the drilling fluid is less than or equal to 10:100. ### Claim 14 A method for sealing a subterranean wellbore, the method comprising: introducing a drilling fluid into a subterranean wellbore, the subterranean wellbore positioned adjacent to a subterranean petroleum formation, where the drilling fluid comprises: a base fluid comprising an aqueous solution; a formaldehyde-based resin, where the weight ratio of the formaldehyde-based resin to the base fluid is from 1:100 to 50:100; introducing a water-insoluble acid catalyst precursor to the drilling fluid, where the water-insoluble acid catalyst precursor is converted to an acid catalyst in the drilling fluid in an amount operable to transition the drilling fluid from a liquid state to a gelled state; where the ratio of the water-insoluble acid catalyst precursor to the total weight of the drilling fluid after the contacting step is from 0.5:100 to 20:100; and where the drilling fluid transitions from the liquid state to the gelled state when a pH of the drilling fluid is less than 6. ### Claim 15 (depends on 14) The method of claim 14, where the water-insoluble acid catalyst precursor is initially contacted with the drilling fluid outside of the subterranean wellbore. ### Claim 16 (depends on 14) The method of claim 14, where the pH of the drilling fluid prior to the addition of the water-insoluble acid catalyst precursor is from 8 to 12.