Oil mud displacement with blast furnace slag/surfactant

A method for drilling and cementing a well comprising:

• drilling a wellbore utilizing an oil based drilling fluid, thus producing a used oil based drilling fluid to be displaced out of the borehole;
• combining ingredients comprising seawater, blast furnace slag having a particle size such that it exhibits a Blaine specific surface area within the range of 4,000 cm.sup.2 /g to 9,000 cm.sup.2 /g, an anionic surfactant, an activator system comprising 2 to 6 lbs/bbl of caustic soda in conjunction with 2 to 20 lbs/bbl of soda ash, a chrome-free lignosulfonate dispersant, prehydrated bentonite clay, a sulfonated lignite/resin dispersant and fluid loss agent, and a polymer-grafted lignosulfonate fluid loss additive to produce a cementitious slurry;
• disposing a pipe within said borehole;
• passing said cementitious slurry into said borehole thus at least partially displacing said used oil based drilling fluid by direct fluid contact with said cementitious slurry;
• and
• displacing said cementitious slurry into an annulus surrounding said pipe by direct fluid contact with a seawater displacement fluid.

A method for drilling and cementing a well, comprising:

• drilling a borehole utilizing an oil based drilling fluid, thus producing a used oil based drilling fluid;
• combining a portion of said used oil based drilling fluid with blast furnace slag, a surfactant and an activator system to produce a cementitious slurry;
• disposing a pipe within said borehole;
• passing said cementitious slurry into said pipe in direct fluid contact with said used drilling fluid;
• introducing a displacement fluid into said pipe in direct fluid contact with said cementitious slurry;
• and
• displacing said cementitious slurry down said pipe and up into an annulus surrounding said pipe.