塔里木盆地大北地区激发药量选择

Determining explosive quantity in Dabei area,Tarim basin

在塔里木盆地以往的地震数据采集中,对激发药量的确定缺乏具有理论指导的科学选择方法,从资料品质这一角度出发,往往会选择较大的药量。为此,在塔里木盆地库车坳陷大北地区的三维勘探中．从理论和试验上对激发因素进行了细致的分析。首先,对地震波在地层中的衰减规律进行了理论分析,探讨了仪器接收系统对信号的可记录性,给出了这些因素对激发子波能量的要求；然后,根据爆破工程理论,讨论了不同围岩和激发药量对激发子波的影响；最后,在野外进行了针对性的试验,根据试验结果,确定了激发药量的选择原则,即①衰减后的目的层反射波振幅应满足仪器接收系统对信号的可记录范围；②目的层的反射波能量要远远大于勘探区的环境噪声；③不同的激发岩性采用不同的激发药量,以保证整个勘探区域地震子波振幅相对一致。根据该原则,分别对大北地区的戈壁砾石区、砂泥岩出露区和西域组砾岩出露区的激发药量进行了科学合理的选择,获得了较好的激发效果,资料的品质得到了改善。

In the former seismic data acquisition in Tarim basin,theoreti- cally guided method to determine the explosive quantity was not found.The determination of the explosive quantity was based on data merely,often resulting in a larger amount of explosive than it was really needed.In order to solve this problem,explosive quanti- ty is carefully analyzed theoretically and experimentally in the process of the 3-D prospecting in Dabei area of Kuche depression, Tarim basin.First,the attenuation rules of seismic waves in strata were theoretically analyzed,the recording ability of receiving sys- tem on signals was researched,and the requirements of these fac- tors on shooting wavelet energy were given.Then,the influence of different surrounding rock and explosive quantity on shooting wavelets was discussed in terms of explosion engineering theory. Finally,pertinent experiment was carried out in field and the prin- ciple of determining explosive quantity was set by the experimental result,that is 1) the reflection amplitude of target after attenuation should satisfy the recording range of receiving system to signals,2) the reflection energy of target should be much higher than environ- ment noise in the exploration area,3) different explosive quantity should be adopted for different lithology to ensure that the ampli- tudes of the seismic wavelets in the whole exploration area can be relatively the same.According to this principle,the explosive quantity of the Gobi gravel area,the sand-mudstone outcropping area,and the western conglomerate area in Dabei is selected re- spectively.By doing so,good shooting results are obtained and the section quality is improved.