Vinyl sulfonate amide copolymer and terpolymer combinations for control of filtration in water-based drilling fluids at high temperature

摘要

A water-based clay drilling fluid or mud suitable for drilling at temperatures up to 200 DEG C. and pressures up to 100 psig at pH levels from 8 to 11.5, said mud or fluid containing additives which are two separate and distinct water-soluble vinyl sulfonate amide polymers. One polymer consists of a random distribution of units of the formulae <IMAGE> <IMAGE> <IMAGE> The other polymer consists of a random distribution of units of the formula (a) and (b) as described above. In each polymer, R1 and R2 are the same or different and each is hydrogen, methyl, or ethyl, and X+ is a cation. Drilling while using this improved fluid or mud results in a reduced fluid loss rate.