Research On The Signal Quality Of Continuous Wave Mud Pulse Generator

The continuous wave mud pulse transmission technology has the advantages of energy concentration,long transmission distance,fast speed and strong anti-interference ability,and has become an important research contents for measurement while drilling and logging.The measurement data is encoded and modulated to pressure wave signals through a rotating valve of the pulse generator.The pressure signal is transmitted from the downhole to the ground system through drilling mud,and the ground system performs signal detection,acquisition,processing and demodulation-decoding.The influence of source and channel on mud pulse signal quanlity were analyzed in this thesis,in order to improve the quality of continuous wave mud pulse signal.The main works and conclusions are shown as follows:Firstly,the research status of continuous wave mud pulse generator was introduced,and the necessity of developing continuous wave mud pulse generator with independent intellectual property rights and a deeply analysis of the characteristics of research status of drilling fluid channel characteristics was put forward.Secondly,the factors affecting the quality of mud pulse signal are analyzed from both source and channel.In the source,combined with the generation mechanism of continuous wave mud pulse signal,the influence of motor speed control accuracy on the quality of mud pulse signal was analyzed,and the quantitative relationship between indicators is established.The attenuation law of mud pulse signal in channel and the effect on the mud pulse signal by the abrupt section of drilling pipes were analyzed.Then,the quantitative relationship between the performance index of the motor speed control system and the quality evaluation index of the mud pulse signal is established.Based on the PID control algorithm,the motor speed control performance index is determined,and the theoretical model of quantitative relationship between indicators is established.The regression model of quantitative relationship between indicators is established by curve fitting,and the regression model is optimized,and is used to replace the complex theoretical model and to guides the motor control and source signal quality evaluation.The channel characteristics and the influence of different channel structures on the signal are studied.Due to the large number of elbow structures in the ground system,the reflection and transmission of the pressure wave signal in the elbow section are analyzed.The results show that the mud pulse signal has a very high transmittance in the elbow section,and the elbow has little effect on the amplitude and phase of the transmitted signal,so in the subsequent research,the elbow section is simplified into a straight pipe.According to the wave equation and the continuity equation,the attenuation law of the mud pulse signal in the transmission channel and the reflection and transmission law of the mud pulse signal at the abrupt section of groud systems are analyzed.Finally,the necessity and feasibility of improving pulse signal quality are analyzed.The method of improving the quality of pulse signal is analyzed from three aspects: combined the quantitative relationship between indicators with the signal processing capability of the ground signal processing system,the motor control index is optimized;the dynamic selection of the signal carrier frequency is realized according to the actual drilling depth;drilling process parameters such as mud viscosity and density rate are optimized under the conditions of drilling operation.