Any of several methods for increasing the productivity of oil wells (after pumping is no longer effective) by emulsifying as much as possible of the oil trapped in the rock structure. Techniques that have been researched and used to some extent involve the pumping into the formations of pressurized carbon dioxide, water, steam, detergent solutions, brine, and a mixture of various high polymers, guar gum, xanthan biopolymer, bauxite, or sand. Considerable success has been achieved, but such methods have proved to be both slow and inefficient.See Chemical Flooding; Hydraulic Fracturing.