Appeal No. 94-4409
Application 07/958,526
where each R’ is individually selected from H or methyl, and
circulating said drilling fluid in a bore hole during the
drilling of a well wherein said fluid encounters hostile
conditions as defined by a temperature and divalent ion
concentration above the infinite days line of FIGURE 14.
45. A process comprising forming a drilling fluid
comprising water, clay and polymer produced from a monomer
composition consisting essentially of at least one hydrophilic
N-vinyl lactam and at least one 2-acrylamido-2-methylpropane
sulfonic acid or the sulfonate salts thereof, and circulating
said drilling fluid in a bore hole during the drilling of a
well wherein said fluid encounters hostile conditions as
defined by a temperature and divalent ion concentration above
the infinite days line of FIGURE 14.
66. A drilling fluid comprising
(a) a base fluid comprising water and an
insoluble weighting material and
(b) water-soluble polymer present in the range
of about 0.5 to about 5 lb/bbl produced from a monomer
composition consisting essentially of at least one hydrophilic
N-vinyl lactam, at least one hydrophilic unsaturated amide
selected from the group consisting of monomers represented by
the formulas,
O
R? - C - NH2
where R? is an unsaturated radical and
3
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