| Traditional metal mineral exploration depends on gravity, magnetic, electric and other methods, generally adapting in the shallow. When the probe target depth increases, abnormal strength and resolution sharp decline because of the limitation of the method itself. So it is difficult to adapt to the needs of deep mineral exploration. Seismic exploration method has great depth, high resolution, and is accurate and reliable, is the most promising technology in deep mineral exploration.To verify the feasibility of seismic exploration in metal mineral region, we carried out seismic experiment on Luohe, Nihe and Dabaozhuang deposits in Luzong area, including seismic data acquisition, processing, interpretation, geological geophysical model construction, seismic wave field modeling and other research.Compared with the oil seismic exploration, the seismic exploration in metal mining area has its own technical difficulties:Such as geological structure in metal mining is often very complex, stratigraphic continuity is poor, the detection targets is small, rock alteration is serious, subsurface heterogeneity is very strong, and mine has usually a serious background interference. Seismic interpretation of metal mining is very difficult for the low signal to noise ratio of seismic data, the lack of marker beds and log data.Seismic data acquisition generally occurs in mountainous or hilly areas where volcanic metamorphic rocks have complex geological structure. Field data acquisition should select reasonable shot position and acquisition parameters based on circumstances and parameters test, and ensure receivers coupled well with the ground, ensure acquisition quality.Metal mining seismic data processing, through the specific analysis of SNR, frequency, interference wave, static correction. NMO correction, velocity et al., and the application of specific measures, while processing seismic data of metal mining, data quality has been significantly improved, structural features is also more clear. Reasonable application of prestack and post-stack noise removal, the SNR of seismic data is improved; application of "no-ray tomography inversion static correction" technology, static correction problem due to elevation changes and low-velocity layer thickness is better resolved in the study area, and the continuity of phase axis is improved; The application of high-precision interactive velocity analysis and residual static correction of frequency splitting, more intuitive and more accurate stacking velocity picking, can solve the speed picked up and short wavelength static problem in the low SNR region; Application of "no stretch NMO" technology can solve the shallow imaging problems affected due to removal of the stretch distortion, shallow data improved greatly.Since the study area have more information of boreholes and petrophysical measurement data, mining model is conducive to carry out seismic modeling. Select boreholes nearby seismic lines, and project onto the seismic, and extrapolate to both sides of the rock distribution based on these drilling information, then draw a geological model. Take the petrophysical parameters measurement, and establish reasonable petrophysical parameters library using the statistics results of the relationship of density and velocity, and then convert the geological model to the complex geophysical model by put the petrophysical parameters to the geological bodies; To research the resolution of Seismic methods to the ore body and surrounding rock, complex model will be transformed to a simplified geophysical model.However, the underground media are often not uniform, especially in the metal mining with intense tectonic activity and serious alteration of rock, this heterogeneity is more significant. The homogeneous medium mode established is often not meet with the actual ground conditions. Random media is a typical heterogeneous medium, it is mainly considered under the conditions of small-scale. Autocorrelation function, scale, variance (or standard deviation), roughness coefficient are the four elements for the random algorithm. Roughness coefficient from small to large, local media change from rough to smoothing; Variance more larger, the disturbance of velocity is more larger; The relation of horizontal and vertical scale reflects the overall distribution of the media, when the ratio of horizontal and vertical scale is several times, the media shows like layered distribution with intermittent disturbances, when the horizontal scale is much larger than the vertical scale, the media presentation layer distribution; Different angle of the random medium can more accurately reflects the direction of subsurface media disturbance characteristics. Discuss the influence of random parameters to the forward modeling of seismic wave field by establishing a variety of mining random medium models.Seismic wave field modeling technique have important theoretical and practical significance, for its visual image to reflect the characteristics and the law of subsurface wave field propagation, people understand the wave field characteristics of the ore bodies, to explain the seismic data, characterization of subsurface structure and lithology. Geological structures are complex in metal mining, ore body shape is changeable, SNR is generally low, characteristics of composite waves is less obvious, seismic interpretation is very difficult. Compared to the results of forward modeling and practical information to help understand and identify characteristics of various seismic wave field.The various theoretical models are modeled using wave equation with staggered-grid finite difference method, and then do wave post-stack, the pre-stack time migration of p-wave and pre-stack time migration of converted wave. The results showed that:phase axis is intermittent partly in complex model, but the reflection information of overall shape of ore bodies and the main objective layers can be seen; The phase axis is more continuous and clearly in simplified model, highlight the reflection information of ore bodies and the main objective layers; The wave field is very complex in random medium model, resulting in many small reflections, is more similar to practical information in form, Some reflection of ore bodies and the layers with larger impedance difference can be still seen in the migration profile. Energy of CMP stack section in an tilted layer and ore bodies does not have the correct homing, diffraction phenomenon is obvious, so needed for migration; Kirchhoff post-stack time migration can generally replace phase axis and determine the distribution of ore bodies; Kirchhoff pre-stack time migration is better to focus the energy, has clearer phase axis; Converted wave pre-stack time migration significantly improve the resolution, while the reflection of ore boundary is more continuous, the reflections of the lower boundary of ore bodies and the steep angle layers are more clearly, converter Wave energy is relatively stronger where in the lack of p-wave reflection energy place; So p-wave Kirchhoff pre-stack time migration and converted wave pre-stack time migration should be combined to do interpretation.Discuss the influence of frequencies and random parameters to seismic wave field, through changing the seismic wave dominant frequencies and random parameters. Found:the higher the frequency, the seismic resolution is better, when the seismic wave frequency is higher than 70Hz, some internal reflection of the orebody can be distinguished; When random variance is greater than 5%, the majority reflection of volcanic layer submerge in the random medium wave field, but still able to see the ore body reflection for the large impedance difference between ore body and surrounding; When the horizontal correlation length is large, generate intermittent liked layered seismic wave field; when roughness coefficient is greater, the random medium on smooth, the messy phenomenon of seismic wave field has been declined. Through the establishment of steep-shaped ore bodies random medium model, and the forward modeling, the reflection and scattering characteristics within the ore bodies can be seen when the random variance of ore body is much larger than the surrounding rock. So when the random variance is large difference, steeply dipping ore bodies can be detected using seismic methods.Carry out geological interpretation based on regional geology and drillhole information near the seismic line, combined with forward simulation and actual data characteristics of the seismic wave field, and found that the deposition red basin's "Kei-like" structure and the internal hierarchical structure and volcanic 3 layers structure. Attribute analysis of migration profiles can found that the different nature of the rock significantly different dynamic characteristics. From the frequency, the sedimentary rock is rich in low frequency, there are also low-frequency components in the volcanic region covered with quaternary, and volcanic region without quaternary coverage is lack of low frequency, high frequency information is relatively rich in volcanic areas. Sedimentary areas is better continuity of phase axis, the energy intensity, volcanic areas is poor continuity, and has some messy strong energy group. Wavelet time-frequency analysis can better observe the energy characteristics of different reflection region of the each frequency band profile.Generally speaking, the large and relatively flat ore bodies may generate effective information in the seismic reflection profile. And volcanic structures is very important to control the mineralization. If it can be effectively detected, then will provide useful information for prospecting. There are still some problems of direct detection of ore bodies, because of the complexity of the subsurface reflection, the core of the problem is how to distinguish between ore bodies reflection and other reflections. So when the seismic exploration method is used in unknown area, the tracking and detection of known ore-controlling geologic body or structures in the deep extension is more credible.
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