The present disclosure relates to compositions and methods for the removal of deposits from oilfield apparatus and wellbore surfaces. In particular, removal of deposits comprising heavy hydrocarbon materials and finely divided inorganic solids. The composition includes a mixture of a corrosion inhibitor component which is morpholine or a morpholine derivative having corrosion inhibitor properties, and a surfactant which is a quaternary ammonium compound having biocidal properties. Methods of removing a deposit from a surface or unplugging an oilwell which has been plugged with a deposit, are also included wherein the method comprising contacting the deposit with a composition as disclosed herein for a selected period of time.