Research Of Control CO₂Breakthrough In101Block Of Daqing Yushulin Oil Field

The average permeability of the reservoir in101block of Yushulin oil field is below1.5×10"3μm2. And water flood can’t work effectively. For that we have to avoid test field from being flooded by CO2. But the characteristic of reservoir and CO2result in gas breakthrough easily. Once that happened, the sweep volume and flood efficiency would be decreased greatly. It would affect exploration effect. Whether gas breakthrough can be controlled is the key factor of gas injection achievement. This article is based on the research of the character of Yushulin101block. By researching gas breakthrough characteristic and key factor, the best anti-plug-breakthrough, we get several conclusions through research. By theory research and simulate experiment of cusping breakthrough of CO2flood, we researched the basic principles which affected CO2cusping. The higher the permeability it is, the easier it is going to happen. When the permeability and the other conditions are the same, the higher of the CO2flood speed, the easier cusping is going to happen. CO2cusping factor is greater than N2cusping factor. If permeability differential was more than15, the injected CO2would all be extracted from high permeability zone, and the sweep efficiency would be very low. By researching geology character and gas-breakthrough rules of shu-101block, we are sure that CO2breakthrough is mainly affected by partly area split and intense nonhomogeneity of sand body. Two bubble formula systems which are acid-proof and oil-proof have been established. The bubble volume of SD-5formula is400ml when pH=3and oil percentage is60%, and its half-life period is83h. By optimizing injection parameter, the best ratio between gas and liquid is1:1～3:2. Three wells were selected to do experiments in the oil field. The effect of decreasing-gas increasing-oil and anti-plug-breakthrough was good. Among them, injection pressure of shu96-C15increased to5.8MPa. Gas injection profile was modified greatly. Injection actuating pressure improved0.5MPa. Index curve slope improved greatly. Bubble plugged the breakthrough channel effectively. After bubble plugged the channel, sweep volume increased from7.3×104m2to9.0×104m2, and gas displacement front advanced to shu97which were not affected. The CO2content and ratio between gas and oil of target well shu96-C16decreased greatly.