Structure Optimization Design of Pulseoscillation Amplifier for Hydraulic Oscillator Based on Numerical Simulation| Stephy Publishers

 


Trends in Petroleum Engineering- (TPE)| Stephy Publishers


Abstract

Hydraulic oscillator is one of the effective tools to solve the problem of high friction in directional drilling and horizontal drilling. However, there are some problems with this kind of tools such as high pressure loss and insufficient vibration force. Because of its self-excited oscillation characteristics, pulse oscillation amplifier can realize the amplification of pulse jet pressure under the condition of lowpressure loss, which is one of the effective ways to solve the above problems of hydraulic oscillator. In this paper, according to the working characteristics of hydraulic oscillator and the demand of pulse amplification, the structure of pulse oscillator amplifier was optimized based on numerical simulation method. Firstly, the geometric and numerical models of the pulse oscillator amplifier were constructed, and the flow field distribution and pulse amplification effect of the pulse oscillation amplifier under different structural parameters were simulated and analyzed, and the influence of different structural parameters on the pulse amplification effect was explored. Secondly, the structure of the pulse oscillator amplifier was optimized by Response Surface Method, and the optimal structure based on the effect of outlet pressure amplification was obtained: upper nozzle diameter D1=22mm, upper nozzle length L1=26mm, lower nozzle diameter D2=28mm, lower nozzle length L2=28mm, cavity length L=58mm, cavity diameter d=80mm, angle 60°. Its pressure loss was 0.3MPa and outlet pressure peak value was 4.5MPa, which was 1.8 times of the inlet pressure peak value of 2.5MPa. Finally, the minimum relative error between the experimental results and the numerical simulation results was 4%, which has verified the credibility of the numerical simulation and structural optimization results.

Keywords

Pulse oscillation amplifier, Numerical simulation, Structure optimization design, Response surface methodology

Introduction

With the acceleration of unconventional oil and gas exploration and development process, the drilling of horizontal wells accounts for about 70% of the total number of drilling in the world, and the length of horizontal section is increasing year by year.1 In the process of long horizontal section drilling, with the increase of well deviation angle and open hole section length, problems such as increased friction, serious overburden pressure and reduced ROP are becoming increasingly prominent, which seriously affect the well quality and drilling cycle.2 By modulating the hydraulic pulse, the hydraulic oscillator uses the hydraulic energy to make the drill string vibrate axially, so as to reduce the friction during the horizontal section drilling, which is one of the effective means to solve the above problems.3–5 But at present, the tool has the problems of high-pressure loss and insufficient vibration force.6 If a pulse oscillation amplifier7,8 was added to the hydraulic oscillator, the self-excited oscillation characteristics of the pulse oscillation amplifier can be used to amplify the pulse pressure without significantly increasing the overall pressure loss of the tool, thus improving the vibration force and reducing drag effect.At present, the research on the pulse oscillation amplifier mainly focuses on the self-excited oscillation mechanism9,10 and numerical simulation method.11–14 Scholars have preliminarily proved its self-excited oscillation mechanism. On this basis, the point vortex and vortex ring numerical simulation models are proposed, which can simulate the self-excited oscillation flow field under the actual working conditions, and become an effective means to study the pulse oscillation amplifier. As the structure andsize of the pulse oscillator amplifier are the key factors affecting the effect of pulse amplification, the optimization design needs to be carried out comprehensively according to the working conditions, pulse characteristics and pressure amplification requirements of the hydraulic oscillator. Therefore, it is necessary to use the numerical simulation and design of experiment methodology to study the influence of structural parameters on the pulse amplification effect and pressure loss according to the working characteristics and pulse amplification requirements of the hydraulic oscillator, so as to optimize the structure of the pulse oscillation amplifier with low pressureloss and high pressurization effect.

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