With the gradual failure of CO2 huff and puff wells, the overall oil exchange rate shows a downward trend. In order to maintain the good effect of the measure and extend its technical life, CO2 synergistic huff and puff are proposed. For complex fault-block reservoir, it is characterized by small oil-bearing area, incomplete well pattern and broken geological stricter. Based on the reservoir feature, synergistic mode is proposed. By using numerical simulation method, typical simulation models of CO2 synergistic huff and puff are established to simulate the effects of geological factors and development factors on CO2 huff and puff. Then we summarized well selection principle of CO2 synergistic huff and puff. The sensitivity evaluation results show that the reservoir rhythm, inter-well passage, well spacing, high-position well liquid production rate and waist well liquid production rate are extremely sensitive factors, the stratum dip and the injection volume allocation scheme are sensitive factors, and the relationship with structural isobaths is insensitive. For well selection, the reservoir with large formation thickness and large stratum dip should be considered primarily. Then a well located in high structural position and with a well spacing of less than 120 m is the optimal choice. Field application at C2X1 block shows a good performance with a total oil increment of 1280 t and the average water cut reduction of 57.7%.
Keywords CO2 synergistic huff and puff, complex fault-block reservoir, implementation mode, well selection principles, field application