砂岩型铀矿地震勘探中若干问题研究

Study on some problems in the seismic exploration of sandstone type uranium deposits

相比于常规的石油和煤炭地震勘探,砂岩型铀矿地震勘探过程中存在着诸多难点问题:勘探目标层埋藏深度浅,一般小于1000 m,浅层地震资料信噪比低,且易受采集噪声的影响;目标层砂体与围岩的物性差异小,致使有效的地震信息较微弱;砂泥薄互层多,砂岩型铀矿往往存在于"泥砂泥"、"煤砂泥"等互层结构的砂体之中,且含矿砂层厚度通常较小,在十米至几十米不等,识别难度较大.据此,开展了大量的地震数据采集、处理和解释技术试验以及应用研究工作,基本明确了从采集面元优化、精细叠前去噪和速度分析方面解决目标层埋藏深度浅所致问题;从采集覆盖次数优化和保幅处理方面解决物性差异小所致问题;从采集的激发和接收参数的优化、提频处理以及波阻抗反演方面解决砂泥薄互层所致问题.实际应用效果证明采用的技术方案具有一定的针对性,是砂岩型铀矿地震勘探有效可行的技术手段.

There are some problems in the sandstone uranium seismic exploration,compared with conventional oil and coal seismic exploration. For example,a. the buried depth of target layer is shallow,generally less than 1000 m,which making the signal-to-noise ratio of shallow seismic data descending and bringing the noise in field raw data; b. the difference of physical properties between target layer sand body and surrounding rock is small,which causing the effective seismic information become weak; c. the sandstone uranium was often born in the thin layers of sand and mud,and the thickness of target layer is small,ten meters to tens of meters,which lead to trouble in distinguishing the sandstone. In view of the above,the large amount of technology experiment and application research of seismic data acquiring,processing and explaining was executed,the problem caused by the buried depth of the target layer was solved by the optimization of the acquisition bin size,the precision of the prestack noise and the high precision velocity analysis; the problem caused by the difference in physical property was solved by the optimization of coverage and protection of amplitude; the problem caused by the thin layers of sand and mud was solved by the optimization of excitation and receiving parameters in acquisition,raising frequency processing,and p-wave impedance inversion method. The practical results show that the technical scheme has certain pertinence,and it is an effective and feasible technical means for seismic exploration of sandstone type uranium deposits.