相控震源在矿产勘探中应用的数值模拟研究

为满足深部矿区精细勘探的需求,研究适于矿区的震源技术至关重要.在便携式电磁驱动可控震源应用于矿区勘探过程中,单电磁驱动可控震源和组合震源分辨率不高.本文基于相控震源技术,采用有限差分方法,对二维地下空间不同介质模型的波场传播及地面接收点的响应进行数值模拟.模拟中,震源分别使用单震源、延时时间为0 ms及1.33 ms的9单元相控源,介质模型采用均匀、水平层状、不规则矿区模型,得到如下结果:均匀介质下相控震源激励定向地震波,0 ms、1.33 ms延时参数下相控源激发固定方向地震波,方向分别为90°和70.4°;层状介质模型下,0 ms参数下相控源产生的垂向地震波方向不随介质变化,1.33 ms相控源激励的定向地震波在不同介质中仍然具有方向性,但随波速变化,地震波发生偏折,地震波主波束方向由70.4°,依次变为68.5°,66.0°,63.7°,61.1°;不规则矿区模型下,1.33 ms相控源激发的地震波在首层介质内传播方向为70.4°,围岩内为65.4°,矿体内为63.1°.在水平层状矿区介质结构下,与单震源相比,1.33 ms和0 ms相控源令接收点信噪比分别提高了14.1 dB和10.2 dB;在不规则矿区模型下,1.33 ms和0 ms相控源较单震源令接收点信噪比提高了18.9 dB和14.9 dB.由此得到如下结论:相控源在复杂介质模型下仍具有激发定向地震波的能力,尽管波束方向在不同介质内会发生偏折;在多种延时参数下,相控源都具有改善接收数据信噪比的能力.综上所述,相控震源技术能有效提高矿集区的数据采集质量.

Numerical simulation of application of the Phased-array Vibrator System in mineral exploration

To meet the demands of sophisticated exploration of deep mineral resources in Deep Exploration Projects of China, seismic controlled source technology is an essential technology. Seismic resolution ratio of single vibrator and combination are not enough in the process of portable vibrator applied to mine exploration. Based on Phased-Array Vibrator System (PAVS), the paper adopts the finite-difference method to carry out numerical simulation of wave propagation and the response of detector in different two-dimensional medium models. We have made numerical simulation of the single vibrator, 0 ms and 1.33 ms 9-unit phased-array in models of homogeneous, multi-layered and irregular mining, respectively. The results are as follows: PAVS produce directional seismic wave in the homogenous model. The main beam direction is 90° and 70.4° for time delay parameters of 0 ms and 1.33 ms. In the model of layered medium, the direction of main beam of 0 ms PAVS is vertical and does not change. Seismic waves of 1.33 ms PAVS are still directional in multi-layered media. When the wave velocity changed, bending waves occur. Directions of seismic waves changed from 70.4° to 68.5°, 66.0°, 63.7°, and 61.1°. In irregular mining model, directions of seismic waves of 1.33 ms PAVS are 70.4° in first floor, 65.4° in surrounding rock and 63.1° within ore mineral body. In layered model, 1.33 ms and 0 ms PAVS increases the SNR by 14.1 dB and 10.2 dB compared with the single vibrator. In tilt mining model, 1.33 ms and 0 ms PAVS increases the SNR by 18.9 dB and 14.9 dB compared with the single. Thus we get a conclusion that seismic waves of PAVS are directional in complex media, although the direction of the beam will deflect in different media. For a variety of time delay parameters, PAVS have the ability to improve the SNR of seismic data. According to the numerical simulation results, PAVS can effectively improve the quality of seismic data in ore cluster area.