Method for control of fluid loss and gas migration in well cementing

A method of cementing a borehole which penetrates a subterranean formation said method being comprised of the steps of:

• forming a cement composition comprised of hydraulic cement in water;
• placing said cement composition in said borehole adjacent said formation;
• permitting said cement composition to set in said borehole whereby a hardened mass of cement is produced;
• wherein said cement composition is comprised of water, hydraulic cement and an additive, said additive being comprised of a copolymer or a terpolymer polymerization product of a first vinyl-containing monomer with one or two other different vinyl-containing monomers selected from a second vinyl-containing monomer, a third vinyl-containing monomer and a fourth vinyl-containing monomer, wherein said first vinyl-containing monomer is a vinylamide morpholine derivative, said second vinyl-containing monomer is a vinylamide derivative, said third vinyl-containing monomer is an N-vinyl,2-ketoheterocyclic derivative and said fourth vinyl-containing monomer is a vinylacid derivative;
• and further wherein
• said vinylamide morpholine derivative is selected from compounds represented by the general formula ##STR9## wherein R.sub.1 is --H or --CH.sub.3 and R.sub.2 is --CH.sub.3 or --CH.sub.2 CH.sub.3 and is positioned on any one of the four carbons in the ring;
• said vinylamide derivative is selected from compounds represented by the general formula ##STR10## wherein R.sub.3 is --H or --CH.sub.3, R.sub.5 is --H, --CH.sub.3 or --CH.sub.2 CH.sub.3, and R.sub.4 is --H, --CH.sub.3, --CH.sub.2 CH.sub.3, --CH(CH.sub.3).sub.2, --C(CH.sub.3).sub.3 or --C(CH.sub.3).sub.2 CH.sub.2 SO.sub.3 X and X is --H, --Na, --NH.sub.4 or --Ca1/2;
• said N-vinyl,2-ketoheterocyclic derivative is selected from compounds represented by the general formula ##STR11## wherein R.sub.6 is --H or --CH.sub.3, and m has a value in the range of 3 to 6;
• and
• said vinylacid derivative is selected from compounds represented by the general formula ##STR12## wherein R.sub.7 is --H or --CH.sub.3, Z is --PO.sub.3 Y.sub.2, --SO.sub.3 Y or --CO.sub.2 Y, Y is --H, --Na or --Ca1/2 and n has a value in the range of from about 0 to about 3.