沙漠地区地震采集避高就低方法探讨

沙漠地区地表是起伏连绵的沙丘,在沙丘的高部位,疏松干燥沙层(低降速带)的厚度可达几十米至上百米,而在2个沙丘之间的谷状地带低降速带的厚度一般只有几米。随着低降速带厚度增大,地震采集的激发条件和接收条件也随之变差,在一定程度上制约着地震资料信噪比的提高。地震采集施工过程中,根据沙丘分布情况,在一定的约束条件下,将部分激发点和接收点设置到沙漠的较低洼部位,避开较厚的低降速带,即避高就低,能有效改善激发和接收条件,取得更好的地震勘探地质效果。通过实际资料来说明高大沙丘对地震资料品质的影响,并从理论上探讨如何根据勘探目的层参数和勘探精度要求来规范避高就低方案。

Discussion on the method of "dodging thick LVL and moving from high places to the lower" in desert seismic acquisition

Rolling dunes are met everywhere when seismic acquisition is carried out in deserts. The depth of loose and arid sand, i.e. LVL depth, can reach tens of meters in the thick parts of the dunes, whereas it is only several meters in the valleys between dunes. When the LVL thickness increases, the shooting and receiving conditions deteriorate, which to some extent restrains the data quality from improving. In order to dodge the thick LVL, some shooting and receiving points are moved to the lower places according to the scattering of dunes, which can effectively improve the shooting and receiving conditions and in turn yield desired seismic and geologic effects. This is called "dodging thick LVL and moving from high places to the lower". This paper analyzed the effect of high dunes on seismic data, and discussed theoretically how to design the scheme of "dodging thick LVL and moving from high places to the lower"according to the requirements of target parameters and surveying accuracy.