METHOD OF REDUCING LOST CIRCULATION DURING WELL DRILLING

• US 3,818,998 A
• Filed: 06/27/1972
• Issued: 06/25/1974
• Est. Priority Date: 06/27/1972
• Status: Expired due to Term

• Current Assignee: James E. Hessert
• Original Assignee: James E. Hessert
• Inventors: Hessert, James E.
• Primary Examiner(s): Sutherland, Henry C.
• Assistant Examiner(s): Ebel, Jack E.
• Application Number:
  US05/266,684
• Time in Patent Office: 728 Days
• Field of Search: 166/294 175/72,64 252/8.5LC
• US Class Current: 175/72
• CPC Class Codes: C09K 8/512 containing cross-linking agents
• CPC Class Codes: E21B 21/003 Means for stopping loss of drilling fluid plastering the borehole wall E21B33/138

Abstract

Water-dispersible cellulose ethers, polysaccharides and polyarcylamides can be crosslinked by contacting with a hexavalent chromium compound and a polyhydric alcohol. Crosslinking results in the formation of a rubbery gel which swells in the presence of water. By introducing the gell into a permeable subterranean zone, to which drilling fluid is being lost during a drilling operation, and contacting it with water, the gel can be caused to swell and reduce the permeability of the zone.

Claims

2. a water-dispersible polyacrylamide, and

3. A method of claim 2 wherein the ionic polysaccharide is B-1459.

4. A process according to claim 1 wherein said hexavalent chromium compound is selected from the group consisting of ammonium chromate, ammonium dichromate, the alkali metal chromates and dichromates, chromium trioxide, and mixtures thereof.

5. A method according to claim 1 wherein said polyhydric alcohol is selected from glycols, polyoxyalkylene glycols, glycerols, and mixtures thereof.

6. A method according to claim 5 wherein said reducing agent is a mixture of one part by volume glycerol and four parts by volume methylene glycol.

7. A process according to claim 1 wherein the amount of said hexavalent chromium compound is in the range of from about 0.5 to 60 weight percent of the amount of the polymer used and the amount of reducing agent is from about 0.1 to about 200 weight percent of the stoichiometric amount required to reduce the hexavalent chromium compound to the trivalent state.

8. A method according to claim 1 wherein said gelling occurs in the presence of water not exceeding about 100 weight percent of the amount of polymer used.

9. A method according to claim 1 wherein said reduction occurs in the presence of an acidic accelerating agent.

10. A method according to claim 9 wherein said acidic accelerating agent is dilute hydrochloric acid.

11. A method according to claim 1 wherein said polymer gel is comminuted and comprises particles from about one-eighth to one-fourth inch on the side.