摘要
为改善低频声波沿钻杆管壁的传输性能,分析了影响声遥测的阻尼机制。考虑钻杆内外沿轴向流动的钻井液的阻尼影响,引入流体的粘性阻尼力,建立了一维纵波波动方程。基于圆柱源辐射理论,研究纵波的径向耦合损耗,并将地层等效为Kelvin粘弹性介质,应用有限单元法求解时域波动方程,讨论了钻井液粘性阻尼和粘弹性地层边界对行波传播特性的影响。理论分析表明,径向辐射和由此产生的波型耦合是声阻尼损耗的主要形式,地层粘弹性系数的变化对低频特性影响很大,但并不改变信道通阻带交替的梳状滤波器频谱。
Effect of damping mechanism on transient acoustical behavior of periodic drill pipes was analyzed including drilling fluid,radiation loss and downhole boundary conditions.A one-dimensional longitudinal wave equation and cylinder source radiation theory were developed to determine fluid viscous loss due to the axial motion of the pipe surfaces in the drilling fluid and radiation loss due to the radial motion coupled to the longitudinal motion.In addition,a Kelvin constitutive equation was used to model the earth layer.Then,the response of the drill strings to the excitation with downhole viscoelastic boundary condition was discussed using a time-domain algorithm based on finite element method.The simulation results show that the radiation loss and coupled vibrations dominate the viscous acoustic damping loss,and the earth layer viscoelastic coefficients are quite sensitive to low frequency response.However,the presence of losses still keeps the comb filtering properties of drill strings.
出处
《振动与冲击》
EI
CSCD
北大核心
2006年第6期17-20,共4页
Journal of Vibration and Shock
关键词
钻杆
声遥测
钻井液
阻尼损耗
有限单元法
粘弹性
drill string,acoustic telemetry,drilling fluid,damping loss,finite element method,viscoelastic
