Abstract
The early monitoring of downhole overflow can be effectively realized by the downhole annular electromagnetic flow detection system. In order to improve the accuracy of the electromagnetic measurement system of downhole annular flow, it is important to optimize the excitation system and electrodes of this system. This research focuses on the optimization of the electrodes for the electromagnetic measurement system of downhole annular flow, whose excitation system has been optimized. First, the basic principle of electromagnetic measurement of downhole annular flow is analyzed. Then, the influence of different positions of the four-point electrodes on the virtual current distributions is analyzed, and the optimum electrode positions and distributions are introduced. On this basis, the influence of shape and size of the large electrode on virtual current density distribution is analyzed. Based on the theoretical study of the influence of electrode on virtual current density distribution, taking hemispherical electrodes and arc electrodes as examples, this paper optimizes hemispherical electrodes and arc electrodes with different shapes and sizes by using finite element simulation method, and proposes three indexes to evaluate the annular virtual current density distributions when the electrodes of different shapes are used. The optimum parameters of shapes and sizes of the hemisphere electrodes and arc electrodes under specific structures of the downhole annular electromagnetic flow measurement system are obtained. This research has great significance for the optimization of electrodes in the downhole annular electromagnetic flow measurement system, and can also be used as reference for the electrode optimization of the traditional electromagnetic flowmeter.
Highlights
With the development of the world economy, the demand of countries around the world for energy is increasing, and the oil exploration and development has been expanding continuously
ΦAB is the potential difference of 2 signal electrodes, W is the weight function, vis the flow rate of the drilling fluids, τ is the annular space of conductive solution, B is the magnetic intensity, and j is the virtual current density vector
If the vector weight function can be constant, the output voltage of the underground annular flow electromagnetic measurement system is only related to the integral of the flow velocity in the annular flow channel, rather than the distribution of the flow velocity
Summary
With the development of the world economy, the demand of countries around the world for energy is increasing, and the oil exploration and development has been expanding continuously. ΦAB is the potential difference of 2 signal electrodes, W is the weight function, vis the flow rate of the drilling fluids, τ is the annular space of conductive solution, B is the magnetic intensity, and j is the virtual current density vector. Based on this theory, if the vector weight function can be constant, the output voltage of the underground annular flow electromagnetic measurement system is only related to the integral of the flow velocity in the annular flow channel, rather than the distribution of the flow velocity. Through the model analysis, when the angle between the electrodes 2γ is increased from 60◦ to 90◦,the area with uniform virtual current potential increases, and when the angle between the electrodes is increased from 90◦ to 120◦, the area with uniform virtual current potential decreases, so 90◦ is the best distribution angle
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