Experimental Simulation of the Zones Characteristics Considering Oily Bubble Behavior During in Situ Combustion

摘要

A linear combustion tube experiment with halfway fire extinguishing was utilized to reconstruct the combustion region distributions based on apparent characteristics of burnt oil-bearing quartz, temperature profile, and oil saturation field distribution between a gas injection well and a production well, etc. The gas composition and fluid composition in each region could be obtained. Following, a high-temperature-high-pressure visualization system was utilized to simulate experimentally the flue-gas flow in the crude oil. A flow characteristics simulation using such process parameters as system injected fluid composition and temperature condition based on the above test results of the combustion tube was conducted. The characteristics of each region were qualitatively described, the flow characteristics of the flue gas was visualized, and the oil bubble enhancement mechanism causing crude oil movement with flue gas was semiquantitatively determined. The results of the combustion tube simulation showed that at least five different coexistent transient regions were observed. Considering that some of the flue gas was dispersed in crude oil in the form of microbubbles, there are burnt zone, burning zone, cracking zone, oil bank, oily bubbles zone, and initial zone. On the basis of microscopic visualization experiments of flue gas flow with crude oil, the effects of flue gas composition, temperature, pressure, and crude oil viscosity on oily bubbles were investigated. The flue gas dispersed in crude oil in the form of stable microbubbles, and the oil carried by the microbubbles presented special oil incremental ability. The denser and the more stable the oily bubble is, the stronger the oil carrying capacity of the bubble is. The results show that the distribution of nitrogen bubbles is the densest, the distribution of carbon dioxide bubbles is the sparsest, and the distribution of the mixed gas bubbles is between the two. The increase of the temperature is not conducive to oily bubble development. The greater the pressure is, the more stable the oil bubble is. The greater the viscosity of crude oil is, the more stable the oil foam is. The experimental results provide theoretical support for further study of the mechanism of in situ combustion.