Method of drilling and cementing a well using a drilling fluid convertible in place into a settable cement slurry

A method of drilling and cementing a well using a drilling fluid thermally convertible in place into a settable cement slurry, comprising:

• drilling a well with a rotary bit through which an aqueous drilling fluid is circulated, said fluid comprising an aqueous drilling mud containing in intimate admixture therewth (i) cement in an amount ranging from about 2 to about 100 pounds per barrel of said fluid and (ii) a deflocculant in an amount ranging from about 3 to about 60 pounds per barrel of said fluid, said deflocculant being deactivatable upon exposure to temperatures above about 300.degree. F.;
• suspending a casing in said well;
• removing said fluid from inside said casing;
• and
• applying sufficient extrinsic heat to said fluid in place within the well annulus to deactivate said deflocculant, thereby converting said fluid in place into a settable cement slurry.

A method of drilling and cementing a well using a drilling fluid thermally convertible in place into a settable cement slurry, comprising:

• drilling a well with a rotary bit through which an aqueous drilling fluid is circulated, said fluid comprising an aqueous drilling mud containing in intimate admixture therewith (i) cement in an amount ranging from about 5 to about 50 pounds per barrel of said fluid and (ii) a metal lignosulfonate present in an amount ranging from about 6 to about 30 pounds per barrel of said fluid;
• suspending a casing in said well;
• removing said fluid from inside said casing;
• and
• applying sufficient extrinsic heat to said fluid to deactivate said metal lignosulfonate, thereby converting said fluid in place into a settable cement slurry.