Study On Ternary Combination Huff And Puff Technique Of Ultra-Heavy Oil Reservoir

About 5159×10⁴t reserve of ultra-heavy oil with viscosity larger than 10×10⁴ mPa·s hasn't been developed because of large viscosity, deep and thin layer, which shares 38% of undeveloped heavy oil reserve and is one of the major undeveloped resources, since the ternary combination huff and puff technique composed of oil-soluble viscosity reducer, CO₂, steam is invented and applied successfully in Shengli Oilfield. Research on the mechanism of separate or cooperative effect of oil-soluble, CO₂ and steam to ultra-heavy oil and improving the ternary combination huff and puff technique is quite necessary for developed this kind of reservoir efficiently.The density, viscosity, asphaltene structure, four fractions mass fraction and molecular weight of ultra-heavy oil were systematically researched by laboratory experiment. Oil-soluble combined viscosity reducer for ultra-heavy oil was developed based on the properties of ultra-heavy oil, which is powerful for decreasing viscosity under the conditions of low water cut, high water cut and high temperature. As rate of viscosity reduction has the shortage on describing viscosity reduction ability for ultra-heavy oil, multiplying factor of viscosity reduction was employed. A new equation of state for CO₂ is conducted which is better than PR and RSK equation of state on predicting CO₂ state. CO₂ solubility in ultra- heavy oil or emulsion with different water cut, swelling factor, density, viscosity of ultra-heavy oil dissolved CO₂ was systematically researched by laboratory experiments. The results show that CO₂ can dissolve in, swell ultra-heavy oil and considerably reduce the viscosity of ultra-heavy oil. Water cut has negative effects for CO₂ dissolving in and swelling ultra- heavy oil emulsion, but has positive effects on reducing viscosity. The experiment results show that the cooperation of two of Viscosity reducer, CO₂ and heating is more efficient on improving rheological properties of ultra-heavy oil than single. The ternary combination huff and puff technique has ability on disaggregation of big molecule in ultra-heavy oil, decreasing the rate and the molecular weight of resin and asphaltene, increasing the rate of saturate and aromatic. The simulation model of ternary combination huff and puff was created according the basic geological data, property data of compositions, disaggregation data and IFT reduction data of viscosity reducer. The effect on improving recovery of ultra-heavy oil reservoir and injected parameters of viscosity reducer, CO₂ and steam were studied by the simulation model of ternary combination huff and puff. The ternary combination huff and puff technique was evaluated by production data of ultra-heavy oil reservoirs in Shengli Oilfield which have successfully applied this technique.