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Vibration amplitude variation graph with flow Fig. 10 shows vibration amplitude and displacement when theoretical speed is 300 rpm, 600 rpm and 900 rpm, and the vibration frequencies are 15 Hz, 10 Hz and 5 Hz with the same flow rate 1 L/s. The stable amplitude of the hydraulic oscillator are 0.7 mm, 0.3 mm and 0.2 mm, in line with the aforementioned simulation results. With increasing speed and vibration frequency, the vibration amplitude variation becomes smaller, but with gradual increase of the compression spring, reflecting that the exciting force also becomes larger.
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Resource reserves can be effectively controlled through slim borehole horizontal drilling, which can significantly reduce costs and enhance efficiency. Therefore, it has been widely used in petroleum, geothermal, shale gas and water resources exploration. But the large friction between the drilling string and borehole can cause downhole accidents....
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Context 1
... the experiment, the vibration shaft will vibrate stable after it compresses near the equilibrium. According to the corresponding amount of compression spring, the exciting force can be calculated under this condition. Therefore, spring compression directly reflects the exciting force. Let the rotational speed be 300 rpm, 600 rpm and 900 rpm, with the flow being 0.5 L/min, 1 L/min and 1.6 L/min. The changing laws of the vibration amplitude and excitation force are examined through the experimental device, which will be compared with the simulation results. Fig. 9 plots the displacement and vibration amplitude when the rotary speed is 600 rpm, that is, when the vibration frequency of 10 Hz, and flow rates are 1 L/s and 1.6 L/s respectively. When the rotational speed is 600 rpm with the flow rate of 1 L/s, the vibration amplitude generated by the oscillator is about 0.3 mm. When the flow rate is 1.6 L/s, the vibration amplitude is about 1.4 mm. With increasing flow, the spring compression becomes larger, reflecting the exciting force becomes larger. The experimental results well agree with the simulation results as shown in Fig. 8. Fig. 11 shows the law of pressure drop with flow and speed. It can be seen from the figure that with a valve at the same speed, the pressure drop at the valve port becomes larger as the flow increases. When the flow rate is the same, as the speed increases, the valve opening pressure drop will slightly reduce. But the overall pressure drop is small, which is between 0.16-0.25 MPa. The results indicate that the design effectively reduces stress loss, helping to improve the drilling efficiency. ...
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Citations
... [1][2][3][4][5][6] Various tools such as agitator have been developed and designed to resolve contradictions and improve the extended limits of horizontal wells. [7][8][9] Engineering applications have shown that a small number of anti-frictional tools, such as agitator, had a certain effect on drilling engineering. [10][11][12] The agitator is a derivative production of the screw motor, which can generate axial vibration with certain frequency and amplitude. ...
The challenges such as large frictional drag, difficult weight-on-bit transmission, and low rate of penetration are frequently met in modern directional drilling, especially in horizontal well drilling. This study presented a nonlinear dynamic simulation model of horizontal well considering the random interaction between drill string and wellbore as well as bit and rock. In this study, the dynamic characteristics of the bottom hole assembly during drilling with and without agitator as well as the working mechanism and optimization parameters of the agitator were simulated and compared. The field application of the agitator is also simulated for the design and working parameter optimization. The results show that using agitator can improve the weight-on-bit transmission efficiency and reduce the frictional drag, tropsh-pressure, and occurrence probability of drill string buckling. The optimal installation position of the ∅172 mm agitator obtained in this study is [200, 300] m away from the bit, the optimum frequency range is [3, 17] Hz, and the optimal impact load is 100 kN.
