Research And Design Of Downhole Pulsed Seismic Source Control System

Borehole seismic method technique is a new geophysical technology, which can receive seismic signals with extremely high resolution, so we can obtain delicate imaging of cross-well structure and small scale geological target such as reservoir. It provides new meticulous detection tools for oil and gas development. Borehole seismic technology development largely depends on the development of the seismic source. The downhole pulsed seismic source that is mentioned in this paper is a new type of thumper seismic source, using the cylinder linear motor as the shot source of seismic wave, which can generate wide band and a variety of seismic waves with enough energy. Compared with the traditional downhole weight drop seismic source, this new weight drop seismic source can be used in a deeper well and has the advantages of simple structure and high vibroseis.This paper carried on the research and design of the downhole pulsed seismic source control system. Firstly, this paper introduced the composition of the downhole pulsed seismic source, then determined the controlled objects such as linear pulsed acceleration shot device, shock wave generator and safety protection, the features and requirements of the controlled objects were introduced in detail. According to the requirements of practical engineering, the mechanical characteristics of the linear induction motor and VVVF control theory is studied systematically. This paper made an in-depth study of the compositions and control signals of the shock wave generator controller, and determined the pushing device control scheme by the work characteristics of the pushing motor during the working process. The control system adopted the modular design method to gradually complete the whole design of the seismic source control system.Secondly, this paper completed the hardward circuit design of the specific converter, shock wave generator controller and safety protection, and analysed the function of the related control circuits. The software design and realization method of generating SPWM wave though DSP and the shock wave generator controller were introduced in detail.Finally, the performance of the downhole pulsed seismic source control system was tested and analyzed, the test results can meet the design requirements. It is obvious that the control system designed in this paper is successful, and it can meet the needs of practical engineering.