Swelling and Viscosity Reduction of Heavy Oil by CO2-Gas Foaming in Immiscible Condition
Swelling and Viscosity Reduction of Heavy Oil by CO2-Gas Foaming in Immiscible Condition
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DOI：
10.2118/179738-pa
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发表时间：
2016-05-01
影响因子：
2.1
通讯作者：
Imai, M.
中科院分区：
文献类型：
--
作者：
Or, C.;Sasaki, K.;Imai, M.
本研究对饱和二氧化碳（CO2）溶液减压产生的重油泡沫进行了研究，因为产生泡沫油有可能提高石油采收率（EOR）。实验以重质原油为原料，在CO2压力小于10 MPa、温度20～50℃的条件下进行，与原始粘度相比，产生的泡沫油的溶胀度从36.8%增加到47.5%，粘度比从79%降低到42%。此外，研究表明，在50℃的饱和压力9.97MPa降压过程中，泡沫油中的CO2微泡在压力低于8.0MPa时开始成核，泡沫油的表观粘度开始下降。将生成的泡沫油暴露在76.8秒(-1)的剪切速率下5分钟，由于较大尺寸的气泡消失，气泡体积密度分布从宽带变为高斯分布，其中气泡体积分布的最大概率密度的气泡直径从80μm减小到小于10μm。然而，即使分布发生变化，粘度比的降低也几乎保持不变；这表明表观粘度强烈依赖于直径小于10μm的微泡。 CO2泡沫油由于其表观膨胀大、改善多孔油流的流动性，使得残余油从不动区流出，有望提高稠油采收率。
In this study, foaming of heavy oil generated by depressurization from saturated carbon dioxide (CO2) solution was studied because generating foamy oil has a possibility of developing an enhanced oil recovery (EOR). The experiments were carried out by with a heavy crude oil at CO2 pressure less than 10 MPa and a temperature from 20 to 50 degrees C. The swellings of the generated foamy oils increased from 36.8 to 47.5% with reducing viscosity ratio from 79 to 42%, comparing with original viscosity. Furthermore, the investigation shows that CO2 microbubbles in the foamy oil started nucleating at pressure less than 8.0 MPa during depressurization from the saturation pressure of 9.97 MPa at 50 degrees C, and the foamy oil started decreasing the apparent viscosity. By exposing generated foamy oil under the shear rate of 76.8 seconds(-1) for 5 minutes, the bubble-volume density profile changes from broadband toward to Gaussian distribution caused by disappearing larger size of gas bubbles, where bubble diameter of the maximum probability density of the bubble-volume distribution reduced from 80 mu m to less than 10 mu m. However, reduction of viscosity ratio was almost kept even though the distribution was changed; this shows that apparent viscosity strongly depends on the microbubbles sized less than 10 mu m in diameter. It was expected that CO2 foamy oil has a potential to improve the recovery ratio of heavy oil by making the residual oil flow out from the immobile zones because of its large apparent swelling and improving mobility in porous oil-flow.