Experimental Study On In-situ Generation Of Carbon Dioxide Foam Flooding Technology

The self-generated CO2 foam flooding technology is a new type of enhanced oil recovery technology,which produces carbon dioxide gas in the formation by means of an activating agent and a release agent,and then comes into contact with the foaming agent to produce foam.In this paper,through the selection of gas agent,release agent,foaming agent and foam stabilizer,the self-generated CO2 foaming system was formed and optimized.The influence factors of self-generation CO2 foam system including the concentration of the system,the mixing type and the temperature were studied by the gas generation set.The mechanism of self-generation C02 foam profile control and oil displacement was analyzed by means of sand filling model and visualization model.The effects of permeability,heterogeneity,oil saturation,injection mode and slug size were studied in this paper.Through the above research,the following awareness and achievements:(1)Considering the amount of generated gas,the efficiency of gas generation and the cost factor,the bicarbonate A is a suitable single liquid system.For the double liquid system,under the condition of accelerator excess,bicarbonate A bicarbonate B and carbonate D have the highest gas generation and efficiency,can reach more than 95%.(2)The complex system of anionic-cationic surfactants AM-YY and the anionic surfactant S-AN showed excellent synergistic effect,and had good foam properties.And the foam complex system(0.5%AM-YY + 0.5%S-AN)had the best foaming properties,the foaming volume was 615ml,and the half-life was 5.58min.When the concentration of WP3 was 0.1%,the foaming volume of 0.5%AM-YY + 0.5%S-AN foaming system was 500ml,the half-life was 22.4 min.(3)For the double fluid method of gas generation system,the gas generation rate increases with the increase of gas generation agent concentration and accelerator concentration.The mixing method only affects the speed of the system,the speed of adding gas generation agent and release agent at the same time was fasted,the speed of adding gas generation agent into release agent was second,and the speed of adding release agent into gas generation agent was least.The presence of the gas generating agent and the release agent is the best proportion of the complete reaction,exceeding the optimum ratio of the system and increasing the amount of the releasing agent can not improve the gas generating efficiency.With the increase of temperature,the amount of gas generation increases,the gas generation efficiency and the gas generation speed increases.(4)In the range of permeability(424.4mD?8084mD)in the experiment of single sand filling,with the increase of permeability,the addition of enhanced oil recovery of the in-suit generation of carbon dioxide faom flooding is increased first and then reduced.In the heterogeneity range(3.8?16.9),the addition of enhanced oil recovery is increasing first and then decreasing.When the grade difference is more than 10.7,the control ability of the in-situ generation of carbon dioxide foam is limited,and the additon of enhanced oil recovery decreased.(5)The results showed that with the increase of oil saturation,the oil recovery of in-situ generation of carbon dioxide foam flooding is gradually increased.The amount of enhanced oil recovery of the injectiong the accelerator into the gas agent is the largest.The addition of enhanced oil recovery increases with the increasing of injection volume.When the injection volume increases from 0.1 PV to 0.25PV,the addition of enhanced oil recovery increases rapidly.When the injection volume increases to 0.25PV,the addditional enhanced oil recovery is significantly reduced.(6)The formation of migration and flooding in the porous media is characterized by"continuous formation in migration and uniform flooding".The main mechanism of oil displacement is to inhibit the viscosity fingers,including changing the fluid direction,air resistance effect,stripping oil film,emulsifying and carrying.The profile control mechanism is mainly the formation of the foam in the porous media in the performance of the special rheological and Jia Min effect so that the seepage resistance of high permeability layer increased.This study has a positive guiding significance for the further study and popularization of autogenous CO2 foam flooding technology.