Many difficult technological problems for heavy oil to be produced and transported have occurred due to its high viscosity and serious adhesion onto the flow channel. The fact or phenomenon that the output of foamy heavy oil is higher than that of foamless one implies that the foam existing in the foamy oil has an obvious action on the flow improvement of heavy oil. The major purpose of this study is to investigate and analyze the foam properties, and to verify its action on the flow improvement of heavy oil. Based on the evaluation of foamability, stability and comprehensive performance of the foam, and combined with the analysis of the effects of pH value, mixed salt of NaCl and CaCl2, temperature and MHZ crude oil on foaming comprehensive performance, the optimal formula of foam solution has been screened by using Waring Blender and orthogonal experimental methods. The rheological properties and viscosity-temperature characteristics of various foams, MHZ heavy oil and its foamy oils were measured and analyzed by using rheometer Rheolab QC. The flow improvement mechanism of heavy oil with foam has been discussed by combining with the analysis of the foam properties and its microstructures.

The results show that obvious synergistic actions exist among different foaming agents. For 200ml of the optimal foam solution, its foaming volume is 620ml at the room temperature, the foam half-life is 494min, the foaming composite index is 229710ml·min, and it has stronger resistances to acid, alkali, temperature and oil. The foams and foamy oils show the properties of Non-Newtonian fluid at the studied temperature range and obey the power-law fluid-flow model. The law of the viscosities changed with temperature for different foamy oils is very similar. The higher the temperature and/or the content of the foam solution is, the better the flowability of the foamy oils is, and their highest viscosity reduction rate can reach 96% or above. The apparent viscosity is insensitive to the change of temperature and/or content of the foam solution at the temperature range of 20°C to 30°C. Thus the flow improvement mechanism of MHZ heavy oil with foam can be attributed to the effects of disintegration, isolation and lubrication of the foam on the oil and its flow channels. Therefore, this study provides a theoretical foundation for the development and application of new technologies on the flow improvement of heavy oil.

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