Research On Measurement And Analysis Of Drillstring Vibration

Well drilling is a high input and risk undergroud project, which needs the real-time downhole diagnosis and forecast technique. Drillstring is the information transmission media connecting the downhole drill bit and the top of the drill string. The axial, lateral and torsional vibration of the drillstring can be caused by the drill bit while drilling. Hence, the vibration measured on the top of the drill string contains abundance information of the drillstring, the bit and the formation. The drillstring vibration logging is a new real-time logging technology which can monitor the working behavior of the downhole tools and predict the formation characteristics below the drill bit by analyzing the vibration measured on the top of the drillstring. It's the key element of the drillstring vibration logging that understanding the drill bit vibration property, drillstring transmission property, and processing method of drillstring vibration.On the basis of former research, we carry out research work in the three filed above. Understand the energy and frequency spectrum characteristic of the seismic source by modeling the process of breaking rock with the cone bit; Built the propagation equation of the drill string vibration and study the propagation effect of the drill string; Model the drill string and derive the equation of the downhole vibration force and displace. It shows that propagation matrix model can describe the drill string vibration well; Carry on the field experiment, acquire the drill string vibration, analyze the data with the wavelet method in correlation domain and doconvolved correlation method and obtain the drill string multiples image. It shows that the two methods for analyzing the drill string vibration are effective;Our research demonstrates that the spectrum of the drill bit, the drill string reflected interface imaging and the displace between the drill bit and stone can be used as the main diagnosis parameters of drill bit working condition, the drill string condition and formation characteristics. At last,we attempt to predict the downhole diagnosis. Our research basis the axial vibration of the drillstring caused by the cone bit of vertical well. The result can be helpful to obtain the vibration source in SWD and understand the transmission effect of the drill string.