Abstract:

In order to effectively solve the CO₂ flooding gas channeling in Caoshe Oilfield, two kinds of gas-soluble foaming agents, fluorine-containing foaming agent（agent A） and silicon-containing foaming agent（agent B）, are evaluated from three aspects: dissolution, foaming and plugging, and one of them is selected as the CO₂ flooding sealing system in Caoshe Oilfield. The optimal injection concentration is 1.5 %. According to the experimental results, the solubility of agent A and agent B in supercritical CO₂ under the assistance of the co-solvent, ethanol, reach 2.51 % and 1.93 % respectively, and both of them can form the dissolution conditions of stable foam. The comprehensive performance of foam produced by agent B is better than that of agent A. When the concentration of agent B reaches 1.5 %, the foaming performance is the best. Under the condition of high temperature（110 ℃） and high pressure（15 MPa）, the foaming volume reaches 261 mL, and the half-life period reaches 115 min. From the aspects of dissolution and foaming, agent B is optimized as the foam sealing system of CO₂ flooding in Caoshe Oilfield, and the evaluation experiments of CO₂ foam sealing ability under different injection modes are carried out. When CO₂ and foaming agent are injected alternately as the injection mode, the mixture is more uniform with more foam, and the resistance factor is high and can be more than 40, showing good foaming and plugging performance. The researches of sealing channeling system provide a new technical support for preventing gas channeling in CO₂ flooding of Caoshe Oilfield.

Key words: CO₂ gas channeling, gas solubility, solubility property, foaming property, plugging property