Experimental Study On Microwave Frequency Effect On The Rheological Property Of Heavy Oil

Microwave radiation performance excellent in improving the rheology of waxy crude oil, The microwave is applied to improve the rheological properties of is a new technology. Although the frequency has an important influence on the effect of microwaves, However, the the current study of frequency is still in its infancy. Therefore, investigating the impact of microwave frequency on improving the rheology of waxy crude oil has important implications for the application of microwave in the oil fields.This paper firstly studied the changes of freezing point, viscosity-temperature curve, yield value, flow curve, rheopexy of waxy crude oil through an microwave radiation experiment, the frequency of microwave include 27MHz,235MHz,470MHz,915MHz and 2450MHz. After analyzed the situation that rheology of waxy crude oil improved by all the different microwave frequencies, the result shows a significant effect especially for the cold section. The experiment is to find out that the sensitive frequency of waxy crude oil were 235MHz and 2450MHz. Then the complex permittivity of waxy crude oil was measured at different temperatures to obtain the fitting formula of complex permittivity and frequency. The loss tangent tan5 was calculated by fitting formula,and got the microwave frequency of best thermal effects was about 1400MHz.The mechanism improving the rheology of waxy crude oil by microwave and the impact of frequency on non-thermal were theoretically analyzed. According to the dielectric physics theory, the relaxation time τ was got by calculation and analyzation. Analyzed the variation of the relaxation time τ and considered the range of peak relaxation frequency fR which was 6.90×109～9.10×109Hz by the fitting formula of waxy crude at different temperatures.The waxy crude peak relaxation frequency range was set as preferred frequency band of microwave to improve rheology of waxy crude oil. The relaxation phenomenon was impacted by lagging phase angle θ, resulting in different relaxation phenomena at different frequencies. Through the establishment of the temperature field model, and the action mechanism of microwave on waxy crude was obtained.The experimental and theoretical results show that the frequency of the microwave have a major impact on thermal effects and non-thermal effects of waxy crude oil. The effects of microwaves on waxy crude were influenced by the combined action of microwave thermal effects and non-thermal effects.