Patent ID: 8091644

Claim:
A method for releasing a stuck drill string from a hydrocarbon reservoir wellbore comprising: drilling a wellbore with a drill string in a hydrocarbon reservoir with an OBM; forming a filter cake of OBM particles over at least part of the wellbore, which filter cake contacts the drill string to inhibit movement of the drill string; contacting the OBM and filter cake with a composition for a period of time sufficient to remove at least a portion of the OBM filter cake particles to permit free movement of the drill string, where the composition comprises at least one surfactant and water; and forming in situ an in-situ fluid selected from the group consisting of a water continuous miniemulsion, a water continuous nanoemulsion, and a bi-continuous single phase microemulsion (Winsor IV), where the in-situ fluid further comprises an acid selected from the group consisting of mineral acids, acetic acid, formic acid, polyamino carboxylic acids, salts of these acids and mixtures thereof, and thereby incorporating at least a portion of the oil in the filter cake particles into the in-situ fluid.