Method for control of gas migration in well cementing
AssigneeHalliburton Company
InventorsLarry S. Eoff, Bill W. Loughridge
Life of this patent
Estimating the term…
Abstract
A method of cementing a wellbore which penetrates a subsurface gas-containing formation is provided whereby gas migration is reduced. The method features the use of an additive consisting of a tannin backbone having grafted thereto at least two different vinylamide derivatives. The additive causes the cement slurry employed in the method to exhibit a Zero Gel Time of greater than about one hour, a Transition Time of less than about one hour and controls fluid loss from the slurry.
Claims5
A method of cementing a borehole which penetrates a subterranean gas-containing formation whereby migration of gas from said formation into said borehole is reduced, said method being comprised of the steps of:
- forming a slurry of hydraulic cement in water;
- placing said slurry in said borehole adjacent said formation;
- permitting said slurry to set in said borehole whereby a hardened mass of cement is produced;
- wherein said slurry is comprised of water, hydraulic cement and an additive consisting of a tannin backbone portion having grafted thereto a graft portion consisting of at least a first vinylamide derivative and a second vinylamide derivative selected from compounds represented by the general formula ##STR3## wherein R.sub.1 is --H or --CH.sub.3, R.sub.2 is --H or --CH.sub.3, and R.sub.3 is --H, --CH.sub.3 or ##STR4## said first and said second vinylamide derivatives are different wherein R.sub.3 in said first derivative is ##STR5## and R.sub.2 and R.sub.3 in said second derivatives are both --CH.sub.3.
Dependencies are inferred from the claim text.