Faculty of Computing and Mathematics

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Browsing Faculty of Computing and Mathematics by Author "Fu, Qingqing"

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    A Novel Weak Signal Detection Method of Electromagnetic LWD Based on a Duffing Oscillator
    (Journal of Sensors, 2018-06-21) Wu, Aiping; Mwachaka, Saleh M.; Pei, Yanliang; Fu, Qingqing
    This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The logging while drilling (LWD) electromagnetic weak signal detection model of a Duffing oscillator based on a one-dimensional nonlinear oscillator is established. The influences of noise on Duffing oscillator dynamic behavior of periodic driving force are discussed and evaluate the oscillator weak signal detection mechanism based on a phase change trajectory diagram. The improved Duffing oscillator is designed and applied to detect the electromagnetic logging signal resistivity at the drill bit using the time-scale transformation method. The simulation results show that the nonlinear dynamic characteristics of the Duffing oscillator are very noticeable, the Duffing circuit is very sensitive to detect the tested signal, and it has a reasonable level of immunity to noise. The smaller the amplitude of the tested signal, the more sensitive the circuit is to the signal, the better the antinoise system performance, and the lower the signal-to-noise ratio (SNR).
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    Numerical modeling of electromagnetic wave logging while drilling in deviated well
    (Journal of Ambient Intelligence and Humanized Computing, 2018) Wu, Aiping; Fu, Qingqing; Mwachaka, Saleh M.; He, Xiaoying
    Electromagnetic wave logging-while-drilling (LWD) tools are used in geosteering for hydrocarbon exploration. Comparing with vertical wells, the response of logging has widely changed because the electrical parameters surrounding the borehole are non axisymmetrical distribution in deviated well. In this paper, with the method of alternating-direction-implicit finite difference time-domain (ADI-FDTD), we discuss the logging response of electromagnetic wave LWD in deviated well, three-dimensional Yee’s non-uniform staggered grid is used in cylindrical coordinates, transfer coordinate system is built between strata space and instrument space, which the conductivity tensor of the an isotropic and dipping formation can be expressed in coordinates of instrument, the method of area weighted average is used to compute the effective conductivity of partially-filled grid cells at interfaces, and uni axial perfectly matched layer (UPML) absorbing boundary conditions is used to truncate the computational domain. Result shows that horn of logging response curve is appeared on both upper and lower boundaries, when electromagnetic wave LWD tool penetrating through the boundary with large dipping angle, and this horn is used to indicate the presence of formation boundaries. What’s more, with the eccentric distance increases, horns effect of the boundary is more obvious.
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    A review of mud pulse telemetry signal impairments modeling and suppression methods
    (Journal of Petroleum Exploration and Production Technology, 2018-06-02) Mwachaka, Saleh M.; Wu, Aiping; Fu, Qingqing
    Exploration and drilling operations are the most costly and risky activities that require logging while drilling effective tool operation and high speed real-time data transmission. Among other logging technologies, mud pulse telemetry has been widely adopted into real-time drilling and logging data measurements for deep formation evaluation decision-making. However, the increased down hole information quantity and quality requirements have elevated demands for greater bandwidth and higher data rate transmission. Maximum possible mud pulse telemetry data rates are obstructed by unpredictable signal impairments. Researchers have implemented numerous downhole signal modulation techniques, data compression algorithms and surface receiver noise cancellation techniques to lower bit errors and increase signal-to-noise ratio. This study reviews mud pulse telemetry system signal transmission challenges and current countermeasure trends. Rigorous technical literature reviews from exploration and drilling oilfield service industry have been at the receiving end debated. Mud channel signal characteristics, signal attenuation factors, signal detection and decoding techniques are critical to successful mud pulse operations. To minimize exploration, drilling and economic risks, this study explores mud pulse data transmission challenges, strategies and possible technical solutions to the next generation engineers and scholars in the field.