花海盆地深地震反射剖面的最佳采集参数实验和分析

深地震反射方法是探测地壳深部结构的先锋技术,能获取到莫霍面和上地幔的反射图像,成为揭示岩石圈结构、解决深部地质构造问题的有效手段。花海盆地位于河西走廊盆地群西部,处于不同大地构造单元的交汇部位,地层发育较全,但出露和发育程度差异较大,除白垩系为大面积连续分布外,其他各时代的地层均出露不全,常表现为被侵入岩分割破坏的残块状,为了确定深地震反射在花海盆地适合的采集参数,在采集前开展点试验,进行小、中、大炮炸药井炮激发参数对比优选,最终得到最优化的采集参数。在小炮实验中,36 kg药量取得的反射信息没有48 kg和60 kg的丰富,而且在MOHO反射的清晰度上48 kg和60 kg药量更为清晰,单井激发比组合井激发效果好;在中炮和大炮实验中,不同组合井对比差异不大,随着药量增大,激发能量增大,面波、折射波等干扰波能量也在增大,小炮干扰波能量最弱,反射信息最丰富的,中炮和大炮干扰波较发育,但通过后期去噪处理,也能得到中浅层反射信息。

Experiment and analysis of the best acquisition parameters for deep seismic reflection profiles in Huahai Basin

The deep seismic reflection profiling is a pioneering technique for detecting the deep structure of the crust. It can obtain the reflection fabrics of the Moho and the upper mantle, and hence is an effective method for revealing the lithosphere structure. The Huahai Basin is located in the western part of the Hexi Corridor basin, which is the intersection area of different tectonic units. The stratigraphic development is relatively complete, but the degrees of excavation and development are quite different. Except for the large area continuous distribution of the Cretaceous strata, the strata of other epochs are incompletely exposed, and are often manifested as residual debris damaged by division of intrusive rocks. In order to determine the suitable acquisition parameters for deep seismic reflection in the Huahai Basin, the authors conducted a pilot experiment before the collection, in which the small, medium and large TNT explosives were fired, and wells with different depths were drilled to make comparison. The parameter comparison was preferred, and finally the optimized acquisition parameters were obtained. In the small TNT explosives experiment, the reflection information obtained by the 36 kg dose is not as rich as the information obtained by 48 kg and 60 kg dose, and the results of 48 kg and 60 kg doses are clearer in the clarity of the MOHO reflection, with the single well excitation better than the combined well excitation. In the experiment of medium and large TNT explosives, the contrast of different combination wells does not show much difference. As the dose increases, the excitation energy increases, and the interference wave energy such as surface wave and refracted wave also increases. The interference wave energy of the small TNT explosives is the weakest, but has the most abundant reflection information. The interference waves of he medium and large TNT explosives are more developed, but the middle-shallow reflection information can also be obtained through the noise-suppressed processing.