High temperature filtration control using water based drilling fluid systems comprising water soluble polymers

A drilling fluid system comprising:

• an aqueous base consisting essentially of freshwater;
• a quantity of from about 21 to 58 kg/m3 (7.5 to 20 lb/bbl) plugging agent comprising sulfonated asphalt and lignite;
• bridging agent comprising an amount of water soluble polymer having a 5% by weight Brookfield viscosity in freshwater of from about 50 cP to about 100 cP, the water soluble polymer comprising first olefinic amide monomer copolymerized with monomer selected from the group consisting of sulfonate monomer and a combination of sulfonate monomer and N-vinyl lactam monomer, wherein:
• the first olefinic amide monomer has the following structure:
• wherein R is a 1-alkenyl group and R1 and R2 independently are selected from the group consisting of hydrogen and alkyl groups having from 1 to 4 carbon atoms;
• the sulfonate monomer has the following structure:
• wherein R is selected from the group consisting of polymerizable alkenyl groups having from about 1 to about 4 carbon atoms;
• R1 and R2 are selected from the group consisting of hydrogen and methyl groups;
• and, X is a cation;
• and,
• the acrylate monomer has the following general structure:
• wherein R6 is selected from the group consisting of hydrogen, alkyl groups having from about 1 to about 4 carbon atoms, and groups that activate the unsaturated carbon-carbon bond;
• R7 and R8 independently are selected from the group consisting of hydrogen and alkyl groups having from about 1 to about 4 carbon atoms;
• and, Y is selected from the group consisting of hydrogen and alkali metal;
• and,
• the N-vinyl lactam monomer has the following structure:
• wherein R9, R10, R11, and R12 independently are selected from the group consisting of hydrogen, methyl groups, and ethyl groups;
• wherein, after 16 hours of static aging of the drilling fluid system at about 260° C. (500° F.), the drilling fluid system exhibits a HPHT filtrate of 25 cm3/min or less after 30 minutes at about 149° C. (300° F.).

A drilling fluid system comprising:

• an aqueous base consisting essentially of freshwater;
• bridging agent comprising from about 0.7 to about 29 kg/m3 (0.25 lb/bbl to about 10.0 lb/bbl) water soluble polymer having a 5% by weight Brookfield viscosity in freshwater of from about 50 cP to about 100 cP, the water soluble polymer comprising acrylamide monomer copolymerized with monomer selected from the group consisting of sulfonate monomer and a combination of sulfonate monomer and N-vinyl lactam monomer;
• and,
• a quantity of from about 21 to 58 kg/m3 (7.5 to 20 lb/bbl) plugging agent comprising sulfonated asphalt and lignite;
• wherein, after 16 hours of static aging of the drilling fluid system at about 260° C. (500° F.), the drilling fluid system exhibits a HPHT filtrate of 25 cm3/min or less after 30 minutes at about 149° C. (300° F.).

A drilling fluid system comprising:

• an aqueous base consisting essentially of freshwater;
• bridging agent comprising from about 0.7 to about 29 kg/m3 (0.25 lb/bbl to about 10.0 lb/bbl) water soluble polymer having a 5% by weight Brookfield viscosity in freshwater of from about 50 cP to about 100 cP, said water soluble polymer comprising monomer of acrylamide, monomer of 2-acrylamido-2-methylpropane sulfonic acid or alkali metal salts thereof, and N-vinyl pyrrolidone monomer;
• and,
• from about 21.42 to 57.15 kg/m3 (7.5 to 20 lb/bbl) plugging agent comprising sulfonated asphalt and lignite;
• wherein, after 16 hours of static aging of the drilling fluid system at about 260° C. (500° F.), the drilling fluid system exhibits a HPHT filtrate of 25 cm3/min or less after 30 minutes at about 149° C. (300° F.).

A drilling fluid system comprising:

• an aqueous base consisting essentially of freshwater;
• bridging agent comprising from about 0.7 to about 29 kg/m3 (0.25 lb/bbl to about 10.0 lb/bbl) water soluble polymer having a 5% by weight Brookfield viscosity in freshwater of from about 50 to about 100 cP comprising monomers of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid or alkali metal salts thereof;
• and,
• plugging agent comprising a quantity of from about 21 to 58 kg/m3 (7.5 to 20 lb/bbl) sulfonated asphalt comprising lignite;
• wherein, after 16 hours of static aging of the drilling fluid system at about 260° C. (500° F.), the drilling fluid system exhibits a HPHT filtrate of 25 cm3/min or less after 30 minutes at about 149° C. (300° F.).