Research On Key Techniques Of Three-Component Micro VSP Surface Surveying

As being the main front of oil and gas exploration,mountain areas will continue to be highly valued by the industry for a long time.Such areas have complex topography and varied surface structures,such as steep mountain walls,mobile deserts,huge thick loess,floating populus euphratica forest,farmland water network,and winter ice surface,which cause great difficulties for traditional exploration and development.The complex surface structure not only affects the excitation and receiving efficiency,which reduces the signal-to-noise ratio of field acquisition data,but also seriously affects the validity of the static methods of seismic data,and causes serious interference to superposition imaging,structural interpretation,and reservoir prediction.This paper starts with the trend of multi-wave and multi-component oil exploration in complex mountainous areas and the requirements of surface structure investigation,then systematically studies the three-component micro VSP system,including its basic principles,technical characteristics,construction processes,data processing methods and some technical bottlenecks.Aiming at serious problems,such as difficult orientation of downhole geophones,low SNR of transverse wave,aliasing of longitudinal and transverse wave fields,rapid attenuation of near-surface seismic waves,shallow exploration depth,and poor data quality,some trials were made.In detail,the inertial sensor data fusion attitude detection and orientation were studied,and component data azimuth correction,wave field separation based on particle motion trajectory reconstruction and main vibration energy analysis,automatic gain noise suppression,and data preprocessing and quality monitoring visualization were researched as well.Finally,the full digital three-component micro VSP acquisition system with distributed structure has been developed,which avoids some problems of traditional one,like inflexible,bulky,difficult to transport and inconvenient to maintain.Through research of instruments and processing methods,the following results have been achieved:(1)A three-component digital detector(probe)based on “distributed” seismic acquisition,a data acquisition station(host),control terminals and associated peripherals have been developed to realize the key technologies,such as signal picking and conditioning from high-fidelity weak seismic,suppression of AGC noise,broadband Data acquisition,distributed acquisition synchronization,real-time detection of geophone attitude,and dynamic address adaptive allocation.The developed instrument is of completely independent intellectual property rights,with 6 national invention patents authorized,and the performance index has reached the level of similar instruments at home and abroad.Furthermore,the features such as real-time pose detection,on-line monitoring,and data orientation correction are the original creation in comparison to the same type of instruments.In addition to P-wave exploration,it also has excellent transverse wave acquisition performance,which is very suitable for investigation of the surface structure of complex mountainous terrain and is the optimal solution for multi-wave and multi-component seismic exploration.Currently it has been popularized in CNPC,Chuanqing Drilling engineering company limited and Bureau of Geophysical Prospecting INC.,China National Petroleum Corporation.(2)A special breakthrough has been made in the data processing methods that affects the accuracy of the investigation of the three-component micro-VSP surface.The main research targets were three-component data orientation correction,wave field separation,detector orientation,data preprocessing and visualization methods,and the obtained achievements are: 1)A horizontal component azimuth correction method based on the attitude angle of the detector is implemented,and the horizontal components of the original data are respectively corrected to the source tapping direction and the vertical direction by using the real-time three-dimensional attitude information calculated by the inertial sensor,thereby realizing the enhancement of the data acquisition performance of the shear wave and the converted wave brings the clear recorded phase of the three-component shear wave and the first takeoff jumper clear,the uniform energy distribution,and the significant differences in the longitudinal and transverse wave characteristics,which provide high-quality data for subsequent fine wave field separation.2)A wave field separation method based on particle motion trajectory reconstruction and main vibration energy analysis was implemented,in which the non-main vibration energy and leakage energy in the original data were filtered by the particle motion trajectory reconstruction and main vibration energy analysis.It can greatly improve the signal-to-noise ratio of the target polarization in the original signal,and then we can use Radon and some other methods to perform high-precision wave field separation.3)A high-precision geophone attitude detection method based on inertial sensors and multi-parameter fusion is implemented.The three-dimensional acceleration,angular velocity,and magnetic field information output by the accelerometer,gyroscope,and electronic compass respectively are used to solve the multi-parameter data fusion algorithm.Calculate roll angle Roll,pitch angle Pitch and yaw angle Yaw information of the detector attitude,and display the real-time three-dimensional at the control terminal,survey the state of the detector,guide excitation optimization excitation,based on which to implement the detector three-component hardware orientation and data orientation correction.The three-component hardware orientation and data orientation correction of the detector is one of the characteristics of this system.4)Data collection preprocessing and quality monitoring visualization have been realized.Through software upgrade,data preprocessing functions such as real-time azimuth correction,summarization,filtering,and gain equalization were integrated to make the entire system friendly to man-machine interaction,high execution efficiency,and good expansion.This article has mainly achieved the following innovations:(1)This paper proposes a Geophone attitude detection method by fusing an inertial sensor data and multi-parameter.Through the Combination of different types of data such as electronic compass,acceleration sensor,and gyroscope,the azimuth angle of the detector is solved in real time.Based on which,accurate orientation and azimuth correction are achieved,so that the obtained shear wave data are clearly visible on the same phase and the initial jump is simple.(2)An automatic gain control(AGC)noise suppression technique is proposed.The amplifier gradually and selectively increases the gain over time,which intentionally increases the reflected wave energy.For which,the signal-to-noise ratio of near-surface micro-VSP data Surface investigation depth can be improved.(3)A broadband data acquisition method using an integrator,a high-frequency ADC,a DAC,and a decimation filter is proposed.By constructing a loop filter(modulator),the quantization noise in the high-frequency ADC output data is reshaped and matched.Extract filtering to effectively suppress the out-of-band noise and achieve an overall improvement in accuracy and bandwidth performance.(4)A wave field separation method based on particle motion trajectory reconstruction and main vibration energy analysis is proposed.By filtering the non-main vibration energy and leakage energy in the original data,improve the signal-to-noise ratio of the target polarization wave in the original signal,and then make Radon Transform for the high-precision wave field separation.The method can comprehensively utilize the polarization characteristics and kinematics characteristics of the seismic wave field,realize the effective superposition of multi-component data,and can solve the resolution problem caused by the decrease of the signal-to-noise ratio with the offset variation,especially for poor polarization characteristics of the mountain seismic data,it has a better wave field separation effect.