Design And Application Of Hydraulic Oscillator For Slim-hole Well Drilling

At present,with the continuous development of slim-hole drilling technology,especially in horizontal and ERD wells drilled by coiled tubing,the friction between drill string and wellbore rises gradually with the increase of well depth,resulting in loss of WOB,which is not conducive to the increase of ROP and restricts the development of horizontal well technology.In order to solve the problem of high friction in horizontal drilling,this paper designs a hydraulic oscillator for slim-hole drilling,aiming at the design and application of hydraulic oscillator for slim-hole drilling,and carries out relevant research and analysis.Analyzed the basic structure,working mechanism and possible problems in the operation of oscillating motor.Established the finite element analysis models of the conventional stator bushing and the bushing with equal wall thickness for oscillating short-section motor.The working mechanical behavior of the two kinds of bushing under different internal pressure,temperature and hardness conditions is simulated,which can provide theoretical guidance for the selection of the stator bushing.Combining with the overall flow field structure at the dynamic end of the oscillating short section,the inside flow field is studied based on the flow field model considering of eccentricity and flow rate.The overall modal changes of hydraulic oscillators with two kinds of pitch and lead of motor rotor are compared.Studied the field application of slim-size oscillator,and evaluated the effect of applications in different blocks.The results show that under the same pressure and temperature,the stress and displacement of the same hardness of bushing with equal wall thickness are basically similar to those of the conventional bushing.By comparing the increment,the equal wall thickness bushing has better compression resistance.The simulation of oscillating short joint shows that under the same flow rate,the velocity of the overall flow field increases from small to large,then decreases,and finally tends to be stable at the exit section,the velocity peak is near the eccentric circle.With the increase of eccentricity,the velocity of the interior of the power joint increases gradually,and with the increase of flow rate,the maximum velocity increases accordingly.The smaller the pitch of the rotor,the larger the frequency and amplitude of vibration.When the pitch increases,the vibration and deformation weaken gradually,means the vibration can be greatly slowed down by lengthening the rotor.The optimal WOB and flowrate are optimized according to the theoretical calculations,and the slim-size hydraulic oscillator has been successfully applied in 4 wells of 3 blocks.The drilling speed is faster and the effect is obvious while sliding,also significantly improved the average ROP and shortened drilling cycle of horizontal wells.These results of research can guide to optimize hydraulic parameters of the hydraulic oscillator for slim-hole drilling,to maximize the performance of hydraulic oscillator,and to provide theoretical guidance to design new type of hydraulic oscillator.