Metal Seismic Imaging Based On Inverse Scattering Theory

Metal mine with orogen prolificly, usually has complex features relief surface,its seismic wave propagation is much more complicated than in layered media andthe level of the surface. Metal mines often experience intense tectonic and magmaticactivity, and metal mine has the characteristic of complex metallogenic conditions,complex ore complex shape, small spatial scale (much smaller than reservoirs in thespatial scale), not applicable specular reflection assumption, usually steep tilt andvertical structure. Metal mine seismic exploration copying traditional seismicexploration of oil and gas resources can not get satisfactory results in many cases.The conventional reflection imaging method is limited to large-scale metal structureprediction and effective seismic exploration method is still lacking in steep angle andscale of deposits seismic or geological body smaller than the wavelength. boreholeseismic imaging technology, to some extent, can resolve the problem of steep tilt andvertical structure, but has problems of limited detection range, low detectionefficiency and difficult to promote. Method combined first wave seismiccomography with seismic reflection method is relied on deep seismic reflectionimaging data, structural information at different depths can be effectively reflection,but is limited to the small-scale geological structure upright or steep dip with aserious lack of information reflecting. Scattering method of seismic wave iscurrently still confined to delineatethe non-uniformity of orebody and related mediaat the certain zero offset section conditions (stacked cross-section). Inverse scatteringtheory requires little priori information, and has a greater advantage for compleximaging complex surface geological circumstances, the inverse scattering imagingcircumstances under small perturbations considering the first order term of inversescattering sequence has made significant application effect, but remains to be studiedin the case of large disturbances. Above that, seismic imaging method for practicaluse at the complicated geological conditions of metal mine is not existed. For thescattered wave seismic exploration, the essence is to ultimately solve the inverse scattering inverse problem. Research on complex medium wave propagation andscattering inverse scattering imaging method will be the key for metal mine seismicexploration.The singularity inversion imaging method is introduced to scatter imagingsequence based on the singularity theory and scattering imaging sequence inversionimaging theory.The inverse is linearized by using the small perturbation in singlescattering assumption based on Beylkin’s singular inversion method, according tothe Green function the linearization operator equation is transformed into integralequation. A class of Fourier integral operator is induced, the operator asymptoticexpansion of the first is a singular item containing only the identity operator. A classof causal generalized Radon transform is defined, its adjoint operator is a generalizedback projection operator, and Fourier integral operator is equivalent to the compoundoperation of an integral transformation in the scattering field and generalized backprojection operator.To study the circumstances of seismic wave propagation under complex surfacein complex geological structure, the paper will establish the undulating surfaceseismic wave propagation in complex geological mathematical model.Thetopography of the complex geological seismic wave propagation mathematicalmodel is established, an interpolation method is given for computing normalderivative at the rectangular grid point on the boundary to solve a rectangular gridfinite difference method deal with complex boundary, which is a difficult problemand has been troubled people long; and propagation laws in the relief surface andcomplex media are revealed using the technique of a series of wave field snapshots.A rugged topography and complicated geological model was conducted forsingular inversion imaging numerical simulation.The algorithm of singular inversionimaging for2-D shot seismic record is studied, and the relevant computer imagingsoftware is developed as well. Numerical calculation of inverse imaging of its theorymodel is did, some characteristics and rules of the singularity inversion imagingalgorithm is described. the amount of calculation of the singularity inversion imagingalgorithm of inverse scattering sequence is much larger than the Beylkin singularity inversion method, each item in inverse scattering sequence is a high dimensionalparametric integral, more integral higher of item, and more dimension order, so,usually computing speed of numerical integral is almost unacceptable. According tothe features of the integrand, these high-dimensional integrals are arranged with thehigh dimensional convolution form, and we calculate the high dimensional parametricintegral convolution theorem and the fast Fourier transform method, which greatlyimproves the computational speed. The theoretical model calculation results show thatthe singularity inversion imaging algorithm based on inverse scattering series canconstruct the complex underground medium for effective imaging, and at the sametime suppress the multiple waves in the process of imaging.The mineral seismic field test will be done and both the singularity inversionimaging results and the conventional reflection imaging results will be get andcompared. The mineral seismic field test will be done using French Sercel seismicinstrument and the vibroseis as the source. Two kinds of observation system are testedin seismic data acquisition in the experiments, one is the conventional reflectionseismic observation system of unilateral excitation raceway mode, the other is theobservation system of detector array fixed and shot rolling. The conventionalreflection seismic data of the first kind of observation system are processed to becompared with the imaging results. The singularity inversion imaging of seismicacquisition data containing all two observation system are studied, and good imagingresults are obtained.