Polymer retention and inaccessible pore volume in North Sea reservoir material

Abstract

Among the factors that govern the propagation of a polymer slug through porous media are retention and inaccessible pore volume (IPV). These quantities are sensitive to several parameters which often vary in coreflood experiments. Examples of these sensitivities include the core preparation procedure such as core cleaning and saturation restoration. From corefloods using Brent sandstone reservoir material and a Xanthan biopolymer, the retention of polymer is found to be critically dependent on the cleaning procedure adopted. Solvent cleaning with toluene and methanol gives much higher retention than a depolarized kerosene-brine cleaning routine. Solvent cleaned cores became water wet and the retention at residual oil saturation is 30 μg/g. The kerosene-brine washed core material became oil/mixed wet and the retention is very low, 5μg/g. The retention is not sensitive to the high clay content of 7–16% or variations in the amount of clay. The IPV is found to be insensitive to cleaning procedure, oil saturation, temperature and clay content and is determined to 17%.