Patent ID: 8091645

Claim:
A method of cleaning oil-based mud (OBM) filter cake particles from a hydrocarbon reservoir wellbore comprising: drilling a wellbore in a hydrocarbon reservoir with an OBM; forming a filter cake of OBM particles over at least part of the wellbore; contacting the OBM and filter cake with at least one surfactant, at least one co-surfactant and a polar liquid in the absence of a propionate and the absence of a co-solvent and forming in situ an in-situ fluid selected from the group consisting of a miniemulsion, a nanoemulsion, and a single phase microemulsion (Winsor IV), and thereby incorporating at least a portion of the oil in the filter cake particles into the in-situ fluid, where the co-surfactant is selected from the group consisting of alcohols, glycols, ethoxylated alcohols, ethoxylated glycols, ethoxylated phenols, propoxylated alcohols, propoxylated glycols, propoxylated phenols, ethoxylated and propoxylated alcohols, ethoxylated and propoxylated glycols, ethoxylated and propoxylated phenols, and combinations thereof.