Experimental Study on Formula Screening for Low-Medium Temperature Hybrid Stimulation with Foamy Oil Recreation

The cold recovery factor of extra-heavy oil reservoirs via in-situ generated foamy oil drive is lower than 12% generally. Under the background of “double carbon”, a novel enhancing extra-heavy oil recovery approach, namely low-medium temperature hybrid stimulation with foamy oil recreation, was proposed in this study. The approach would recreate highly dispersed foamy oil behavior by injecting viscosity reducer, hot water, foaming agent, gas and dispersant in a huff and puff mode. And laboratory tests on formula system screening were conducted. The extra-heavy oil samples adopted in the tests were of typical foamy oil features from the Orinoco Heavy Oil Belt in Venezuela. 93 sets of in-door experimental tests were carried out, and the effects of gas type and gas-liquid ratio, foaming agent/dispersant/viscosity reducer type and concentration, temperature and oil saturation on the foamability, foam dispersibility and stability of the formula system were systematically evaluated. The formula system optimized under the experimental conditions consisted of methane gas, naphtha viscosity reducer, KT1 foaming agent and nano-silica particle dispersant. The dispersant could promote the adsorption of foaming agent at the interface, but the dispersant at an excessive concentration would conversely adsorb foaming agent, thus to affect the performance of the system. The preliminary optimized foaming agent concentration was 1 wt%, and the dispersant concentration was 0.5 wt%. Under the condition of oil saturation of 50% and temperature of 100 °C, the regenerated foamy oil exhibited strong dispersibility with an expansion coefficient of 1.37 and a half-life of 1834 min. This study provided a foundation for the further development design optimization of this technology.