Daqing Oilfield has carried out the production of polymer flooding was promoted since in 1996. Presently, polymer flooding is very successful in several production plants of Daqing Oilfield, and getting into industrialization production. It has played a very important role in maintaining the oilfield stable production of over 50 million tons of oil. But the high permeability variation is serious, resulting in polymer production in some production wells recylingly and production concentration increasing slowly, which adversely affects polymer flooding efficiency. Chlloid dispersion gels (CDG) is a unique in - depth permeability modification process. It can reduce in - depth reservoir permeability variation by moving into highly permeable, water saturated zones and providing high resistance to subsequent water injection in those zones, so that oil can be produced from tighter rock. So CDG can enlarge volumetric sweep, and improve oil recovery efficiency. We had a CDG pilot programme in Daqing Oil Field in 1999, now this pilot has been entering into effective period with produing more oil and less water. Introduction Daqing Oilfield has carried out the production of polymer flooding was promoted since 1996. Presently, polymer flooding is very successful in several production plants of Daqing Oilfield, and getting into industrialization production. It has played a very important role in maintaining the oilfield stable production of over 50 million tons of oil. But the high permeability variation is serious, resulting in polymer production in some production wells recylingly and production concentration increase slowly, which adversely affects polymer flooding efficiency. Chlloid dispersion gels (CDG) is a unique in-depth permeability modification process. It can reduce in - depth reservoir permeability variation by moving into highly permeable, water saturated zones and providing high resistance to subsequent water injection in those zones so so oil can be produced from tighter rock. , and improve oil recovery efficiency. We had a CDG pilot program in Daqing Oil Field in 1999, now this pilot has been entered into effective period with produing more oil and less water. Introduction