随钻测量钻井液脉冲传输理论中幂律流体水击方程的建立

针对随钻测量（MWD）系统中钻井液脉冲信号传输方式存在的问题，依据流体力学原理，深入开展了MWD信号传输系统非牛顿流体水击问题基础理论研究。提出了一种线性化处理方法和幂律流体微分黏度近似表达式，建立了幂律流体瞬变流扰动量的变系数线性动量平衡方程，在此基础上建立了幂律流体水击方程。幂律流体瞬变流不仅取决于流体性质，而且还取决于其稳定流流动状态；方程中的变系数揭示了牛顿流体瞬变流与非牛顿流体瞬变流的主要区别。该方程的理论创新之处在于，一是考虑了非牛顿流体的影响，二是没有采用Darcy-Weisbach经验系数计算，而是进行了严格的解析解。

Establishment of Novel Waterhammer Equations for PowerLaw Fluids Inside Pipe in MWD Drilling Fluid Pulse Signal Transmission System

This paper deals with the pulse signal transmission mode for drilling fluids in measurement while drilling (MWD) systems. According to the fluid mechanics principles, the fundamental study on the waterhammer problem of non?Newtonian fluids in the signal transmission system of MWD was deeply investigated. A linear processing method and approximate expression of the differential viscosity for power?law fluids were proposed. The linear momentum balance equations with variable coefficients for the perturbed variables of transientflow of power?law fluids were presented. On the basis of this, the waterhammer equations of the power?law fluids were set up. The results showed that the solutions of transient flow problems for power?law fluids are not only related to the fluids nature, but also depended on flowing state of steady flows. The variable coefficients of the equations showed the main difference between Newtonian and non?Newtonian fluids transient flow. In this paper, the highlights of waterhammer equations for power?law fluids compared to the existing theories can be summarized: the study considers the behavior of the non?Newtonian fluids, and the solution is strictly analytical, so it need not be calculated through the empirical coefficients of Darcy?Weisbach. The proposed theory and evaluation method make up current deficiencies of the waterhammer theory for non?Newtonian fluids. The established theory in this paper provides the basis for the dynamic analysis of drilling fluid pulse signal transmission in MWD systems