Drilling fluids, drilling fluids additives and methods useful for limiting tar sands accretion on metal surfaces
Fluids useful in oil well drilling operations are described. The fluids comprise standard viscosifying and fluid loss control additives along with phosphonates or phosphate esters of organic ligands. The addition of the phosphonates or phosphate esters at effective concentrations prevents the adherence of heavy oil and heavy oil laden drill cuttings to drill pipe strings and well bore casings.
1. A method for drilling a wellbore through a tar sand-containing formation, the method comprising: operating a drilling assembly to drill a wellbore and circulating an aqueous-based drilling fluid through the wellbore as it is drilled, the aqueous-based drilling fluid including a tar sand anti-accretion additive including at least one of (i) a phosphonate and (ii) a phosphate ester of alkanolamine in an amount effective to limit tar sand accretion on metal surfaces.
2. A method for limiting accretion on metal surfaces in contact with tar sand-containing formation, the method comprising: washing the metal surfaces with an aqueous-based drilling fluid, the aqueous-based drilling fluid including an amount of at least one of (i) a phosphonate and (ii) a phosphate ester of alkanolamine.
3. A method for removing accretion from metal surfaces in contact with tar sand-containing formation, the method comprising: washing the metal surfaces with an aqueous-based drilling fluid, the aqueous-based drilling fluid including an amount of at least one of (i) a phosphonate and (ii) a phosphate ester of alkanolamine.
4. The method of claim 1 wherein the tar sand anti-accretion additive is present in the drilling fluid at a concentration of at least 0.1% by weight of the drilling fluid.
5. The method of claim 1 wherein the tar sand anti-accretion additive is neutralized to a pH of 7 to 10.
6. The method of claim 1 wherein the drilling fluid containing tar sand anti-accretion additive is circulated during drilling when tar sand drill cuttings are produced.
7. The method of claim 1 wherein the drilling fluid containing tar sand anti-accretion additive is circulated during drilling of a build section of the wellbore.
8. The method of claim 1 wherein the drilling fluid containing tar sand anti-accretion additive is circulated during drilling of a horizontal section of the wellbore.
9. The method of claim 1 where the phosphate ester is the mono and di phosphate ester of monoethanolamine.
10. The method of claim 1 where the phosphate ester is the mono and di phosphate ester of diethanolamine.
11. The method of claim 1 where the phosphate ester is the mono and di ester of triethanolamine.
12. The method of claim 1 where the phosphonate is ATMP.
13. The method of claim 1 where the phosphonate is HEDP.
14. The method of claim 1 where the phosphonate is EDTMPA.
15. The method of claim 1 where the phosphonate is DTPMPA.
16. The method of claim 1 where the phosphonate is BHMTPMPA.
17. The method of claim 2 wherein the step of washing is carried out by circulating the drilling fluid through the wellbore.
18. The method of claim 2 wherein the step of washing is carried out during drilling the wellbore.
19. The method of claim 2 wherein the step of washing is carried out during running a liner into the wellbore.
20. The method of claim 2 wherein the at least one of (i) a phosphonate and (ii) a phosphate ester of alkanolamine is present in the drilling fluid in an amount of at least 0.1% by weight of the drilling fluid.
21. The method of claim 2 wherein the at least one of (i) a phosphonate and (ii) a phosphate ester of alkanolamine is neutralized to a pH of 7 to 10.
22. The method of claim 3 wherein the step of washing is carried out during drilling the wellbore.
23. The method of claim 3 wherein the step of washing is carried out during running a liner into the wellbore.
24. The method of claim 3 wherein the at least one of (i) a phosphonate and (ii) a phosphate ester of alkanolamine is present in the drilling fluid in an amount of at least 0.1% by weight of the drilling fluid.
25. The method of claim 3 wherein the at least one of (i) a phosphonate and (ii) a phosphate ester of alkanolamine is neutralized to a pH of 7 to 10.
26. The method of claim 3 wherein the step of washing is carried out by circulating the drilling fluid through the wellbore.