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Received Jun 28, 2017; Accepted Oct 18, 2017
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1. Introduction
In recent decades, oil and gas exploration is being carried out in some extremely harsh and challenging environmental conditions [1]. Drilling safety issues become increasingly prominent when exploring complex and deep formations. Downhole microflux control drilling technology can effectively solve drilling accident such as kick and lose in narrow density window drilling scenarios, so using the measurement system to get the real-time information of downhole annular flow is the core and foundation of downhole microflux control drilling technology.
A huge array of flow technology options is on offer which provides options in selecting the correct annular flow measurement for the application of drilling engineering. A broad range of factors regarding the special environment of downhole drilling, such as downhole space, velocity profile, temperature, and fluid properties, should be considered. Electromagnetic measurement has the advantages of simple structure, no moving parts, and no obstruction of fluid flow throttle parts. Also, the flow path does not cause any additional pressure loss, and it does not cause wear or blockage, in particular when measuring slurry with solid particles, sewage and other liquid-solid two-phase bodies, or a variety of viscous slurry, and so on. In addition, because the structure has no moving parts, so any corrosion will be attached to the insulation lining. After selecting corrosion-resistant electrode material with a very good corrosion resistance, it can be used for a variety of corrosive media measurements. In 2017, Liang et al. propose a new method for an annular flow measurement system based on the electromagnetic induction principle [2]. However, this paper does not describe how to design and optimize the downhole annular flow electromagnetic measurement system. Based on the above reasons, this study mainly focuses on the design and optimization of downhole annular flow electromagnetic measurement system for drilling engineering.
For the traditional electromagnetic flowmeter used in a round pipe, the signal voltage is dependent on the average flow velocity, the magnetic flux density, and the pipe diameter. The signal voltage is expected to be linearly related to the average...