Simulation on invasive ERT for void fraction measurement in vertical production oil well

In the development of oilfield, the Production Logging (PL) is mainly to find out the production rate and water cut of each production layer in a multi­layer oil well. It is one of the most important strategies to manage the reservoir, to instruct the well reform and finally to improve the oil production. Usually, electrode arrays are commercially available in the oil production well. For example, there exist CAT (Capacitance Array Tool) and RAT (Resistance Array Tool), which are provided by the oilfield services companies, such as Schlumberger, Halliburton, etc. However, these systems are probe­based and implemented through simple interpretations. As a result, the accuracy is not good enough in the case of low­production wells. Nowadays, Electrical Tomography (ET) has been widely applied in industrial measurements of multiphase flow for its low­cost, rapid response and non­radiation etc.. In the paper, ET will be generalized to the PL. In order to reconstruct the sectional images at different depths, the electrode array cannot be installed on the wall of the well pipe, but fixed on the logging tools which can be transported along the pipelines. In addition, the measurement pipe is metallic and electrically conductive, which serves as an electrical shielding and brings difficulties to the image reconstruction. In the paper, an invasive tomographic sensor for oil PL was designed. It consists of two concentric rings of electrode arrays. A prototype was constructed. Simulations were carried out in the case of bubble flows. Results validated the feasibility of the system by using the proposed sensor cooperating with the image reconstruction method based on the sensitivity matrix.