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Technical Of Identifying The Converted Wave In Multi-wave Seismic Exploration

Posted on:2009-03-28Degree:MasterType:Thesis
Country:ChinaCandidate:Y S LeiFull Text:PDF
GTID:2120360242980221Subject:Solid Earth Physics
Abstract/Summary:PDF Full Text Request
The conventional seismic survey exploited compressional-wave exploration, it utilized only one geophone to record P wave. Multi-wave and multi-component seismic exploration was a new and applying method. This way was different with the conventional method, it used three component geophones to record p wave and shear wave simultaneously .This method can record the wavefield much completely comparing to the conventional way. The multi-wave and multi-component exploration gave us abundant information and it brought many difficulties to seismic data processing at the same time .The vertical and horizontal geophone not only recorded the p wave but also the shear wave in multi-wave survey, and they mixed together. If the data hadn't separated and identified it would went against excursion imaging and geologic identify. Therefore, if we got the seismic data, we had to separate and identify the p wave and shear wave. It was a important step of multi-wave data processing.P-S wave separation was initiated by Dankbaar in 1985.Many methods applied to wavefield separation along with the conception initiated. Now the ways of wavefield separation have two categories: wave-theoretical methods and parameter methods. The methods of parameter included tau-p transform and polarization filtering ,and the method based wave theory had using divergence and curl to separate wavefield. Separating the waves in tau-p field was based on tau-p transform. First transforming the seismic data from spatio-temporal to tau-p, and then selecting right p value to filter based on the p and s wave speed. Finally transform the data to spatio-temporal and then the p and s wave was separated. Polarization filtering was based upon seismic polarization, because different wave had different polarization. The p wave's polarization direction was parallel the wave's movement, but the s wave's polarization direction was perpendicular with the movement .The seismic main polarization or main direction of energy direction could figure out by covariance matrix. The p wave and s wave could separate by design right filter. Using the divergence and curl to separation the wavefild was based on wave equation. The curl of plane p wave was zero and the divergence of plane s wave was zero, so the wavefield could separate by using the divergence to extract the p wave and using the curl to extract the s wave.On the base of the nature of p and s waves , this paper firstly introducing the theory of how the converted wave produced and the characteristic of reflection and transmission when different wave transmit to the reflection. The principle of multi-wave and multi-component exploration was also introduced. After learning the properties of converted wave ,we firstly used polarization filtering to separate the synthesis seismic record and gain not bad result. Then we analyzed and sum up the factors of affecting the result of polarization filtering after separated the p and s wave. Secondly we utilized the tau-p transform to separate the seismic record. Thirdly we used the pseudospectrum method to simulate the seismic wavefild and utilized the curl and divergence to separate and identify the wavefield and analyzed the effect of this method. Finally we compared and analyzed advantage and disadvantage of diversified ways.
Keywords/Search Tags:multi-wave seismic exploration, converted wave, polarization filtering, divergence, curl, tau-p transform
PDF Full Text Request
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