Method and apparatus for extracting downgoing wavelet and attenuation parameters by using vertical seismic data

A method for extracting a downgoing wavelet and attenuation parameters from VSP data, comprising:

• collecting VSP data by placing a three-component or single-component sensor into a well for a seismic wave reception, and using an explosion source or an vibroseis on surface or in the well for a seismic wave excitation near a wellhead;
• picking up, by a processor, a P-wave first arrival from the VSP data to obtain P-wave first arrival time;
• performing, by the processor, upgoing and downgoing P-waves separation processing on the VSP data to obtain downgoing P-wave data;
• performing, by the processor, a FFT on seismic data with a preset time window length starting from the P-wave first arrival time and cut from the downgoing P-wave data to obtain FFT transformed downgoing P-wave data, and obtaining a multi-trace downgoing P-wave log spectrum based on the FFT transformed downgoing P-wave data;
• subtracting, by the processor, a downgoing wavelet log spectrum from the multi-trace downgoing P-wave log spectrum, to obtain a wavelet-corrected multi-trace downgoing P-wave log spectrum satisfying a preset requirement, the preset requirement being that a difference between parameters obtained from the multi-trace downgoing P-wave log spectrum and parameters obtained from the wavelet-corrected multi-trace downgoing P-wave log spectrum is within a preset range, the parameters including intercept and slope;
• performing, by the processor and based on the parameters obtained from the wavelet-corrected multi-trace downgoing P-wave log spectrum, an amplitude correction and an inverse FFT on the FFT transformed downgoing P-wave data to obtain a downgoing wavelet;
• and
• obtaining, by the processor, attenuation parameters based on the P-wave first arrival time and the parameters obtained from the wavelet-corrected multi-trace downgoing P-wave log spectrum, the attenuation parameters including true amplitude recovery factor and Q factor;
• performing, by the processor, deconvolution, amplitude recovery and inverse Q filtering on the VSP seismic data based on the downgoing wavelet, the true amplitude recovery factor and the Q factor, to obtain a seismic image;
• and
• supporting geological interpretation and oil and gas development with the seismic image.