Image Fusion of ECT/ERT for Oil-Gas-Water Three-Phase Flow

The tomographic imaging of process parameters for oil-gas-water three-phase flow can be obtained through different sensing modalities, such as electrical resistance tomography (ERT) and electrical capacitance tomography (ECT), both of which are sensitive to specific properties of the objects to be imaged. However, it is hard to discriminate oil, gas and water phases merely from reconstructed images of ERT or ECT. In this paper, the feasibility of image fusion based on ERT and ECT reconstructed images was investigated for oilgas-water three-phase flow. Two cases were discussed and pixel-based image fusion method was presented. Simulation results showed that the cross-sectional reconstruction images of oil-gas-water three-phase flow can be obtained using the presented methods. phase flow, it is hard for ERT or ECT to obtain good cross-sectional reconstructed images, from which oil, gas and water can be discerned clearly. In order to obtain tomograms of oil-gaswater three-phase flow, an image fusion method was presented in this paper. The conductivity of oil, gas and water is different and that is the case for the permittivity. Based on the fact that ERT is sensitive to the conductivity of objects and ECT is sensitive to the permittivity of objects, it is feasible to obtain the tomogram of oil-gaswater three-phase flow by image fusion based on the reconstructed images of ERT and ECT. The following section describes the feasibility of the image fusion of ERT and ECT for oil-gas-water three-phase flow. After that, the reconstruction algorithms for image generation and the employed image fusion method are described briefly. Finally, simulation results were presented and discussed in detail. DOI: 10.4018/japuc.2011040104 30 International Journal of Advanced Pervasive and Ubiquitous Computing, 3(2), 29-34, April-June 2011 Copyright © 2011, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. 2. ERT AND ECT SENSORS 2.1. The Structure of Sensors The 16-electrode ERT and ECT sensors are depicted in Figures 1(a) and (b). In ERT, the electrodes are mounted equally on the interior of pipe. The measured objects in pipe must be conductive and the electrodes must contact with them. While in ECT, the electrodes are mounted equally on the exterior of pipe. The measured objects in pipe must be nonconductive or most of the mixture of the multi-phase material is nonconductive. 2.2. Image Reconstruction Algorithms There are many different image reconstruction methods for ERT and ECT, which can be mainly classified into two categories, direct methods (linear back projection, Tikhonov regularization and truncated singular value decomposition) and iterative methods (Conjugate Gradient and Landweber) (Yang & Peng, 2003; Marashdeh, Warsito, Fan, & Teixeira, 2006; Wang, Tang, & Cao, 2007). In our study, Landweber iterative algorithm with optimal step length was adopted which is defined as (Liu, Fu, & Yang, 1999): G G S SG k k k T k + = + − 1 η λ ( ) (1)