Optimum Experiment Study On Foam System Of Gel Foam Assisted Gas Flooding In Tahe Fractured-vuggy Carbonate Reservoir

Fractures and solution vuggys are main reservoir spaces in Tahe Fractured-Vuggy Carbonate Reservior,the reservoir temperature is up to 120 ? and the formation water salinity is up to 22×104 mg/L.Had been developed by natural energy depletion mode and water injection development,Nitrogen gas injection was used in Tahe oilfield to supplement formation energy and enhance oil recovery.Because of the gravitational differentiation and strong mobility,the effect of gas flooding is seriously restricted.While gel foam assisted gas flooding technology can delay the gas channeling and make up for the shortage of gas performance.So based on the technology of gel foam assisted gas flooding,the foam formulation system is optimized,and the laboratory effect of foam assisted gas drive is evaluated.Considering of the single factor of formation water,after mechanical agitation by Waring-Blender,foam could be formed effectively.Then poured into simulated formation water with 22×104 mg/L sanility,which was imitated the process of foam contacting formation water after injecting into formation during FAG flooding in Tahe Fractured-Vuggy Carbonate Reservior.Through the experiments of single or compound surfactant agent,the optimal temperature-salt-tolerance foaming agent could be selected.Then,three gels with high strength modified starch gel,medium strength polymer gel,low strength gum gel and PPG were used to optimized the gel foam by a series of static experiments for foam assisted gas flooding.After that,the static evaluation experiments of the selected gel foam were conducted,including oilresistance evaluation,rheological test and high temperature-pressure evaluation.Also,the microstructure of gel foam was observed by scanning electron microscope.Finally,a three-dimensional high-temperature and high-pressure tolerance model of Tahe was designed to verify the feasibility of the optimized foam.The research results shows that comparing to other surfactants,?-A,S-12 and S-16 show better foaming capacity and stability at normal temperature.When ?-A and S-16 are mixed with 1:1 proportion,the synergistic effect is highly remarkable,and foam is reached the most stable state which half life of solution is 600 s under the condition of 22 × 104 mg/L salinity.In the gel optimization experiments,the high strength modified starch gel foam system shows excellent salt tolerance,temperature resistance characters with great fluidy.Under the simulated Tahe formation condition,the halflife of the solution for modified starched gel foam is 3 hours.The results of microscope and electron microscopy show that the liquid film is dense and smooth,which can prevent the foam stability from the intrusion of the crude oil.Gas drive and modified starch gel foam assisted gas drive experiments for three-dimensional model show that the final recovery percent of the latter is 12.6% higher than that of the former.