| The high foreign dependence of oil and gas resources and the backwardness of its exploration and development technology have led China to increase the development of unconventional oil and gas resources.The emergence of deep detection technology of impulse sound source has well compensated for the shortcomings of conventional acoustic logging technology in terms of detection distance and low resolution of seismic exploration technology,promoting the rapid growth of China’s oil and gas resources.The discharge electrode,as the core part of the impulse sound source deep detection technology,deeply affects the impulse sound source characteristics,which in turn affects the detection depth and resolution.Therefore,this thesis focuses on the characteristics of SLC-type electrodes for impulse sound sources,aiming to propose an electrode structure with high intensity,wide frequency band,small size,controllable and repeatable excitation as a detection sound source.The main findings of this thesis and the conclusions obtained are as follows:（1）Theoretical analysis of the discharge phenomenon and discharge process of the impulse sound source,and clarify the discharge breakdown conditions in the liquid.The plasma control equation is established based on the cylindrical plasma channel model and the channel time-varying resistance model.The impulse wave characteristics can be calculated by this equation.（2）The numerical model of impulse sound source discharge is established by using the finite element method for simulation calculations,and the simulation results are compared with the experimental results in the literature to verify the correctness of the model.Thus,the S,L,C type electrode impulse sound source model is established.The study analyzed the impulse sound source characteristics under different experimental parameters and different electrode structures,and it can be seen that the impulse sound source characteristics of S-type electrodes are better than those of L-type and C-type electrodes.（3）The confined space,liquid working environment and external energy storage circuit in the well place higher demands on the electrode gap,electrode diameter,conductivity and charging voltage.These parameters directly affect the detection depth and resolution of the deep detection of impulse sound sources.And thus,the effects of electrode gap,electrode diameter,conductivity and charging voltage on the characteristics of S-type electrode impulse sound source are studied.The results show that there is an optimal electrode gap of 7 mm;under the optimal electrode gap,the increase of electrode diameter prolongs the pre-breakdown time,decreases the impulse wave intensity and energy conversion efficiency;the increase of conductivity only prolongs the pre-breakdown time to a great extent;the increase of charging voltage decreases the pre-breakdown time exponentially,increases the impulse wave intensity linearly,and the energy conversion efficiency1 increases and then decreases.（4）The improvement of the hollowing of the Stick electrode in the S-type electrode enhances the intensity of the inhomogeneous electric field,increases the breakdown voltage,and increases the remaining energy of the energy storage capacitor,thus improving the impulse excitation characteristics.The optimized electrode pre-breakdown time was shortened by25.24%,the impulse wave intensity was increased by 2.56%,and the energy conversion efficiency1 and2 were increased by 54.55%and 30.82%,respectively. |
