The Study of Oil Displacement Characteristics of CDG and Polymer Flooding

Abstract The Colloidal Dispersion Gel (CDG) technology, sharing multiple similarities with polymer flooding, is developed(1) for in-depth profile modification. However, due to the differences in chemical type and concentration, molecular structure and mechanisms, the displacement processes between CDG and polymer are different. The injection capacity of the two processes are about the same, but polymer flooding features large injection increase amplitude, quick pressure increase in initial period and quick decrease for subsequent flooding pressure; while CDG injection features a slower and gradual increase and decrease. The oil recovery effect for polymer flooding is mainly realized during the process of polymer injection, featuring quick water cut decrease and fairly quick increase as well quick water cut increase for subsequent water flooding; the oil displacement effect of CDG is equivalent of that for polymer flooding during chemical injection, but performs much better than polymer during subsequent water flooding. During the initial stage of the CDG injection, the water cut shows multiple stages of decline and then shows a slow increase during the water drive. In addition, water cuts in producers were stabilized for a long period of time. The production cycle for polymer flooding in a pattern with 250 meters distance between injection and production wells is usually about 6 years, while the CDG process lasted over 10 years. Under similar geological conditions, the chemical injection amount for CDG profile modification is 20% less than that of the polymer flooding but the increased oil recovery is about4% over the polymer flooding at the economic limit.