Study On The Pulse Generating Principle Of Mud Pulse Generator

In this article, the mud pulse generating principle of pulse is analyzed.Based on the principle of unsteady flow, non-Newtonian fluid mechanics, transient flow theory, dynamic wave theory and other theories,study the theoretical of the mud pulse signal generation and numerical simulation the transmission process.It has made some progress on the mud pulse generator.The present situation of the downhole transmission method is introduced at first. By comparison the characteristics of the of downhole transmission method and their respective advantages and disadvantages of the downhole transmission method,point out that the continuous wave mud pulse device is the main research directions.According to the unsteady flows principle, the speed calculation formula of the sticky and under ideal mud pulse signal transmission has been put forward.Research shows that the mud pulse transmission speed has related to the the type of the drilling fluid, solid content of the drilling fluid, gas content of the drilling fluid, pulse signal transmission frequency and the and the average friction coefficient. Solid content and gas content of the drilling fluid similar Impact rules on the sticky and under ideal mud pulse signal transmission speed. When the fluid compressibility and fluid density increased, the sticky and under ideal mud pulse signal transmission speed has the decreased trend. When the hydraulic friction coefficient increased, the sticky and under ideal mud pulse signal transmission speed aslo has the decreased trend. the signal frequency and viscosity of drilling fluid significantly influence the signal attenuation extent, the influence of the signal frequency and its changes is relatively larger than the viscosity of drilling fluid and its changes, high frequency signal is more prone to attenuate, the higher the pulse frequency and the viscosity, the bigger attenuation.In the high frequency section, the drilling fluid pulse signal transmission speed is higher and the status of the transmission process is relatively stable, So if can meet the work conditions,we should to try to choose the high-frequency pulse sign.Analysis the generating mechanism of the continuous wavelet pulse signal, according to the theories of fluid dynamics and non-Newtonian fluid mechanics, based on the transient flow theory, we get the calculation model with transmission characteristics, the basic equations of the pulse signal transmission, and the initial condition and boundary conditions. This article uses the method of characteristics and finite difference method for solving equations, using the second-order approximation method for the friction term. It is based on the method of characteristics, compiling Matlab program to analyze pulse transmission. Research results show that:in the process of the pulse signal transmits from the bottom up, amplitude decreases, the pulse signal attenuation, and there is the delay in time. Consider the impact of the system step response, encoding of "11001",reflection at the bit and at the pump, compared the volumetric pump to the centrifugal pumps.Study on the differential detection and downhole testing tools application. Compared the characteristics method to the electronic circuit simulation method, Verified the Correct of the characteristics method.Compared the experimental data to the simulation results of the system step response, encoding of "11001 " and the differential detection, Validate that the experimental results are the same with simulation results.