Developing a microwave tomographic system for multiphase flow imaging: advances and challenges

Since the 1980s, electrical tomographic imaging techniques based on low-frequency capacitance and resistance measurements have been developed for the monitoring of industrial processes and in some cases multiphase flows. Research on microwave tomography for oil and gas multiphase flow imaging began in the mid-1990s, even though the basic principle of microwave tomography was reported a decade earlier for biomedical imaging. In this paper, the development of a microwave tomographic imaging system for such an application since then is overviewed. It is shown by several examples that microwave tomography can effectively reconstruct the images of dielectric objects, moisture distribution inside processed food and oil–gas two-phase flows. It is also shown that the use of higher microwave frequencies would effectively lead to images of higher spatial resolution. Since real-time microwave tomography systems are currently available and ready for industrial applications, the challenges in developing a practical system with higher temporal resolutions suitable for the imaging of high speed multiphase flows in oil industry are highlighted and discussed in both hardware and image reconstruction aspects.