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. The synergistic mode is proposed based on the peculiarity of small oil-bearing area of the fault block reservoir that geological structure is broken, and there is no completed development well pattern. By using the numerical simulation method, typical simulation models are established to simulate the effects of different geological factors and development factors on the performance of CO2 synergistic huff and puff. The well selection principle of CO2 synergistic huff and puff are proposed. The research results of the influencing factors show that the existence of inter-well channel has a negative impact on the stimulation performance, the greater the permeability contrast the worse of oil increasing and water cut decreasing. The injected CO2 has a certain sweep radius and the limitation of well spacing is 70m. There is negative interference between liquid production rate of high structural position well and the performance of lower position well. For well selection of CO2 synergistic huff and puff, 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 70 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