Patent ID: 11880012
Assignee: CHINA NATIONAL PETROLEUM CORPORATION
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 8:
9. An apparatus for extracting a downgoing wavelet and attenuation parameters from VSP data, comprising:
an explosion source or an vibroseis on surface or in a well used for a seismic wave excitation near a wellhead;
a three-component or single-component sensor placed into a well for a seismic wave reception to collect VSP data;
a data acquisition module configured to pick up a P-wave first arrival based on VSP data to obtain P-wave first arrival time, and perform upgoing and downgoing P-waves separation processing on the VSP data to obtain downgoing P-wave data;
a first processing module configured to perform 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 obtain a multi-trace downgoing P-wave log spectrum based on the FFT transformed downgoing P-wave data;
a second processing module configured to subtract 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, wherein the preset requirement is 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;
a downgoing wavelet extraction module configured to perform, 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
an attenuation parameter extraction module configured to obtain 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.