Water based fluids comprising multivalent salts and low molecular weight, low charge cationic polyacrylamide copolymers

A drilling system fluid comprising:

• water as a continuous phase;
• a first amount of a multivalent metal salt;
• a second amount of a monovalent salt, said second amount being sufficient to increase gas hydrate suppression and decrease density when compared to said fluid consisting essentially of said multivalent salt in the absence of said monovalent salt;
• a quantity of water soluble polyacrylamide copolymer having a cationic charge density of at least about 1% and having the following general structure:
• wherein
• R and R1 independently are selected from the group consisting of hydrogen, acrylamide groups, acrylate groups, polyacrylamide groups, and polyacrylate groups, and copolymers thereof;
• R2 is selected from the group consisting of vinyl pyrrolidone;
• vinyl alcohol;
• piperazine;
• aminoethyl piperazine;
• styrene;
• alkyl groups and alkenyl groups having from about 1 to about 6 carbon atoms;
• trimethyl aminoethyl groups;
• alkoxylated alkyl groups and alkenyl groups having from about 1 to about 6 carbon atoms;
• alkenyl alcohols having from about 1 to about 6 carbon atoms;
• piperazines;
• styrene;
• alkoxylated alkyl groups and alkenyl groups having from about 1 to about 6 carbon atoms;
• acrylonitrile groups;
• acrylate and methacrylate groups;
• alkanolamides having from about 1 to about 6 carbon atoms;
• and vinyl amide;
• R3 is selected from groups comprising a charge in the range of from about +1 to about +4;
• and
• n independently is at least 1.

A drilling system fluid comprising:

• water as a continuous phase;
• a first amount of a multivalent metal salt
• a second amount of a monovalent salt, said second amount being sufficient to increase gas hydrate suppression and decrease density when compared to said fluid consisting essentially of said multivalent salt in the absence of said monovalent salt;
• and,
• a quantity of water soluble polyacrylamide copolymer having a cationic charge density of at least about 1% and having the following general structure:
• wherein R and R1 independently are selected from the group consisting of hydrogen, acrylamide groups, acrylate groups, polyacrylamide groups, and polyacrylate groups, and copolymers thereof;
• R2 independently is selected from moieties selected from the group consisting of vinyl pyrrolidone;
• vinyl alcohol;
• piperazine;
• aminoethyl piperazine;
• styrene;
• alkyl groups and alkenyl groups having from about to about 6 carbon atoms;
• trimethyl aminoethyl groups;
• alkoxylated alkyl groups and alkenyl groups having from about 1 to about 6 carbon atoms;
• alkenyl alcohols having from about 1 to about 6 carbon atoms;
• piperazines;
• styrene;
• alkoxylated alkyl groups and alkenyl groups having from about 1 to about 6 carbon atoms;
• acrylonitrile groups;
• acrylate and methacrylate groups;
• alkanolamides having from about 1 to about 6 carbon atoms;
• and vinyl amide;
• R3 comprises a charge of from about +1 to about +4 and is selected from the group consisting of ester groups;
• hydrogen;
• cyclic, linear, and branched alkyl and heteroalkyl groups having from about 1 to about 6 carbon atoms wherein said heteroalkyl groups comprise one or more heteroatoms selected from the group consisting of nitrogen and oxygen;
• cyclic, linear, and branched alkenyl and heteroalkenyl groups having from about 1 to about 6 carbon atoms and resonance hybrids thereof;
• carboxylic acid groups and salts, esters, and amides thereof comprising cyclic, linear, and branched alkyl groups, heteroalkyl groups, alkenyl groups, and heteroalkenyl groups having from about 1 to about 6 carbon atoms wherein said hetero groups comprise one or more heteroatoms selected from the group consisting of nitrogen and oxygen;
• aromatic groups;
• alkanols and alkenols having from about 1 to about 6 carbon atoms;
• alkanolamides and alkenol amides;
• and
• n independently is at least 1.