Study On Vibration Characteristic Of Bottom Drilling String And Design Of Drilling String Shock Absorption & Down Hole Hydraulic Pressurizing System

Down-hole hydraulic pressurizing technology is one of the most effective ways to improve the rate of penetration under the existing conditions of drilling technology. This paper have presented a new kind of concept which will integrate drilling string vibration reducing with bottom hole drilling fluid pressurizing to design a vibration reducing and pressure increasing device based on the study of experiment of bottom hole drilling string vibration characteristics. This kind of device will absorb energy generated from the longitudinal vibration of the drilling string as its own power in the process of drilling, and take advantadge of the longitudinal vibration of the drilling string to achive the to-and-fro movement of the piston located in the plunger pump, as the mean while the drilling fluid get pressurized because of the compress of the vibration of the drilling pressure. Therefore, the effect of bottom hole pressure increasing as well as the effect of drilling string vibration reducing have been gained at the same time. The merit of this new type of device can be describe as the new designed device is more simplified compare to the prior ones with more complicated reversing agent, and it also eliminated another important factor which contribute to the short life cycle of the device, so it must be more suitable to the purpose of down-hole pressure increasing under the harsh working conditions in the bottom hole.This paper commited to the simulated experiment study targeted to the bottom hole drilling string vibration characteristics in straight holes using the bottom hole drilling string dynamics simulated experimental device. Having analysed the data, drilling string vibration characteristics and down-hole drilling pressure alternating regulation have been gained for five sets of BHA under different drilling parameters condition, and presented amplitude range and frequency range for wellbore sized 311.1mm and 244.5mm under normal used drilling parameter conditions. Therefore, this study has presented experimental criteria for increasing down-hole drilling fluid pressure using energy generated by drilling string longitudinal vibration, and presented design criteria for the determination of device parameters. According to the study result of the longitudinal drilling string vibration characteristics, the overall structure of the device has been designed and the intensity check for some crucial parts has been calculated. The operating principle and mechanical structure of the device has been analysed and simulated using SIMULINK and PRO/ENINEER WILDFIRE, as a result the feasibility of the theory of drilling string shock absorption and hydraulic pressurizing has been proved. On the basis of the above research, the design of the all the parts, relative valves, active sealling agents, UHP bit, connecting device, machining drawings, overall assembly drawings and so on have been achived, then the production of drilling string shock absorption and hydraulic pressurizing system and the development of prototype has completed. In the first down-hole experiment in Mesozoic erathem of Zhuanggu 10-58 Well located in Shengli Oilfield, the result proved this type of device can improve drilling speed greatly. The experimental distance is 3457.5m to 3482.5m, and the drilling depth is 25.0m with the average drilling speed of 6.20m/h(the average drilling time of 9.67min/m). The drilling speed is 8.25 times greater than the same drilling distance in the nearby well without the device.