陇东巨厚黄土塬区地震勘探数据采集方法研究
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摘要
陇东巨厚黄土塬区,由于表层地震激发条件复杂多变,潜水面深,反射波衰减强烈,导致目的层反射波难以分辨,为此在陇东地区的多个地震勘探项目中有针对性的进行了多井组合、井深对比、检波器组合等一系列试验及分析研究。结果表明在黄土塬地区可使用中密度成型炸药,多井组合激发,且井越深记录质量越好;检波器采用9串2并或9串线形组合,组内距2m,可有效压制随机干扰;观测系统须根据不同地貌条件进行选择,在黄土塬上宜采用多道、小炮间距、小偏移距、高覆盖等直线观测系统;而在黄土沟、坡中,可采用弯线观测系统,并适当减少道数及覆盖次数、增大炮间距及偏移距等;在沟塬过渡段为避免出现空白段,应采用变观系统。
In the eastern Gansu extra thick loess tableland area, since complex and variable near-surface seismic shot condition, deep groundwater level and strong reflection wave attenuation will cause target reflection indistinguishable. For this reason, multiple seismic prospecting projects in the area should carry out a series of tests and analytic studies including multiwell assemblage, well depth contrast and geophone array etc. The result has shown that the medium density packaged explosive and multiwell multiple shot can be used in loess tableland area, in addition, the deeper the well the better the record quality. The geophone array uses 9 in series 2 in parallel or9 in series line type combination, element interval 2m, thus can suppress random disturbance effectively. Field setup should be selected based on landform, on the loess tableland should use multichannel, small shotpoint interval, small offset and high coverage straight line field setup. While in loess gully, on slope can use slalom line field setup, and appropriately reduce channel number and fold, increase shotpoint interval and offset. In gully and tableland transition zone, to avoid blank zone, shotpoint transferring should be used.
In the eastern Gansu extra thick loess tableland area, since complex and variable near-surface seismic shot condition, deep groundwater level and strong reflection wave attenuation will cause target reflection indistinguishable. For this reason, multiple seismic prospecting projects in the area should carry out a series of tests and analytic studies including multiwell assemblage, well depth contrast and geophone array etc. The result has shown that the medium density packaged explosive and multiwell multiple shot can be used in loess tableland area, in addition, the deeper the well the better the record quality. The geophone array uses 9 in series 2 in parallel or9 in series line type combination, element interval 2m, thus can suppress random disturbance effectively. Field setup should be selected based on landform, on the loess tableland should use multichannel, small shotpoint interval, small offset and high coverage straight line field setup. While in loess gully, on slope can use slalom line field setup, and appropriately reduce channel number and fold, increase shotpoint interval and offset. In gully and tableland transition zone, to avoid blank zone, shotpoint transferring should be used.
引文
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