Hydrophobically modified poly(ethylene glycol) as reactive clays inhibitor additive in water‐based drilling fluids

Adsorption measurements and inhibition tests were used to investigate the mechanisms of shale stabilization by hydrophobically modified poly(ethylene glycol) (PEG). Commercially available PEG with a large range of molar masses and PEG diesters were adsorbed on smectite‐rich clay from saline solutions and the clay/polymer complexes obtained were characterized by thermogravimetric analysis and x‐ray diffraction. The adsorption isotherms obtained for all unmodified PEG showed low affinity for the clay surface, however they all accessed the interlamellar spaces of the clay and reduced the clay water content of the complexes obtained. The PEG macromolecules had their affinity for the clay strongly enhanced by the hydrophobic modification especially with dodecanoic acid and were intercalated into the clay matrix, reducing, in a more efficient way, the water uptake by the clay. Conventional rolling tests were performed to evaluate the effect of polymers on the clay cuttings integrity. Results show that under conditions promoting the adsorption of polymers on both external and interlayer clay surfaces, displacement of the water from the clay was obtained and dispersion and disintegration of clay cuttings were inhibited. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010