摘要
深反射地震是了解深部地质结构的主要手段,获取高品质的数据是给出合理地质解释的基础.在结晶岩地区,由于地层成层性差、非均质性严重,地震散射效应明显,导致地震波场复杂,同时结晶岩为非理想弹性体,不利于地震波能量转换,有效反射能量弱,信噪比低.加之深反射地震的目标层较深且受环境噪声干扰严重,高频信号衰减快,地震资料主频较低.这些因素使得在结晶岩区难以获得高品质的地震资料,为探索提高该类地区深反射地震资料质量的方法和技术,本文依托长江中下游成矿带2009—2014年深反射地震数据采集工作,在精细设计、严格施工的基础上,从激发和接收入手,开展了"轴向不耦合激发"、"宽频接收"和"宽线观测"等技术方法试验研究.结果表明,这些方法技术措施提高了下传弹性波能量,展宽了接收地震信号的频带,提高了覆盖次数和信噪比,有效改善了地震原始资料的品质和成像效果.研究结果对今后结晶岩地区深地震反射数据采集工作具有重要的实用价值和参考意义.
Deep reflection seismic survey is the main method to explore the deep geological structure,in which the high quality data is the basis of reasonable geological interpretation.Due to very irregular and heterogeneous strata in hard-rock environment,the seismic scattering effect is obvious,leading to complexity of the seismic wave field.On the other hand,as non-ideal elastic media,hard-rock rigidity is not conducive to elastic wave energy conversion,so explosive energy is too limited to transfer to elastic waves.Low frequency characteristics of seismic dataassociated with the deeper exploration target can be seriously disturbed by environmental noise,resulting in low signal-to-noise ratio in hard-rock environment.Based on the seismic reflection data acquisition in the middle and lower reaches of the Yangtze River metallogenic belt from 2009 to 2014,this work focused on how to improve seismic raw data quality and signal-to-noise ratio with fine design and careful implementation in hard-rock environment.We have conducted a series of experiments on new methods such as"longitudinal non-coupling exploding","wide band receiving"in the very low SNR region and"wide line acquisition"to improve seismic data quality.The results show that these techniques can enhance the energy of elastic waves propagating downward,expand frequency bands of received seismic signals,and raise coverage times and SNR,which effectively improve the quality of raw data and imaging profiles.It provides the experience and reference for deep seismic data acquisition in hard-rock environment in the future.