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Poly(acrylic acid) and polyacrylamide mixture as oil-well drilling fliud rheology modifiers

Some rheological properties of diluted water solutions of polyelectrolytes based on poly(acrylic acid) (PAA)/ polyacrylamide (PAAm) mixture differing highly in their molecular weight under oil-well drilling conditions have been examined. Depending on the polymer mixture composition, the reduced viscosity-composition diagram separates in two regions, one hydrophilic region where the polymer mixture appears an expansion of its hydrodynamic volume, and another hydrophobic region where the polymer mixture appears a compact complex conformation. The effect is much more pronaounced as the polymer mixture concentration is higher (c = 0.2 instead of , 0 g L-1). The viscosities of the PAA and PAA1/PAAm333 water solutions, increase with dilution, contrary to the behavior of nonionic polymers. However, in an water NaCl solution 1, 0 x 10-2 M L-1 a dramatical reduction of the gel-like interpolymer association region and an enlargement of the compact complex conformation region was observed. Even the slight neutralization of the poly(acrylicacid) ( 5 % and 10 %) eliminate the compact complex region and expand the gel-like interpolymer association region in the whole composition range. Shear rate dependence of the viscosity of both PAA and PAAm and their mixtures has been established under oil-well drilling conditions by using a Roller instrument at 25 oC, 150 oC and 200 oC. The obtained dependence showed a Newtonian plateau at low shear rates from 3.67 to 14.68 s-1. These findings are much more pronounced using polymer mixtures of very high molecular weight for both and also mixtures by the poly(acrylic acid) higher degree of neutralization.

polyacrylamide; poly(acrylic acid); oil production; polyelectrolytes; polymer-polymer complex; viscosity

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