abstract |
Outstandingly suitable drilling mud additives are water soluble copolymers consisting essentially of a random distribution of (a) 5 to 95% by weight of units of the formula <IMAGE> (b) 5 to 95% by weight of units of the formula <IMAGE> and (c) 0 to 80% by weight of units of the formula <IMAGE> wherein R1 and R2 are the same or different and each is hydrogen, methyl or ethyl; and X(+) is a cation. |