A PILOT PROJECT OF CO₂ ENHANCED OIL RECOVERY AND STORAGE IN CHANG 8 EXTRA-LOW PERMEABILITY RESERVOIR IN HUANG 3 DISTRICT OF CHANGQING OILFIELD

In order to evaluate the adaptability and application potential of CO₂ flooding in the extra-low permeability reservoir, Changqing oilfield carried out a pilot project of CO₂ enhanced oil recovery and storage and obtained satisfactory results. Given the surrounding gas source conditions, reservoir conditions, field road and CO₂ trial transportation, the Chang 8 reservoir in Huang 3 district was determined as the pilot test block for CO₂ enhanced oil recovery and storage engineering. The reservoir is characterized by a large scale, abundant surrounding gas sources, and good field road conditions. In addition, the reservoir condition can be able to reach the condition of miscible flooding. However, it is an ultra-low permeability reservoir and in the early development stage, showing a steady decline in the production efficiency by water flooding. The field test result of CO₂ flooding pilot shows that the daily oil production and daily gas production increases significantly, while the water content decreases after CO₂ flooding, indicating that CO₂ flooding has a good prospect for further promotion in Changqing oilfield. Compared to water flooding, the injection pressure is independent with the injection volume and without significant increase, indicating that the test reservoir has a good capacity for CO₂ injection and storage. However, the change of injection pressure is relatively lower than that of water flooding, optimization has to be applied to the parameters of gas injection mode, injection rate and pressure for the further application of CO₂ flooding. In addition, in order to improve the effect of CO₂ flooding and facilitate the overall evaluation of the pilot project, it is suggested that the scale of the pilot project can be further expanded in the future.