关于塔中大沙漠区低速带调查重新定位的思考

Reconsidering the aim and function of low-velocity zone investigation in the massive deserts of middle Tarim basin

（1.中国石油化工股份有限公司油田勘探开发事业部工程技术处,北京100029；2.中国石油东方地球物理勘探公司研究院，河北涿州072750；3.北京帕美智软件开发有限公司，北京100022）

Exploration & Production Department, SINOPEC, Beijing 830011, China

在塔中大沙漠区，小折射和微测井是野外低速带调查的主要技术手段，旨在得到近地表速度分布，指导井深设计和计算野外静校正量。塔中大沙漠区的设计井深一般在潜水面以下1~3 m，利用小折射和微测井技术可以很容易地得到潜水面的埋深。但野外静校正量的计算需要得到替换速度（2 000 m/s）以上所有地层的精细速度分布，由于受到采集密度和探测深度的影响，利用小折射和微测井技术得到的野外静校正量存在较大的误差，野外静校正后的叠加剖面存在长波长静校正问题。为此，用非线性初至波层析反演静校正方法替代小折射和微测井技术，有效地解决了长波长静校正问题。最后，针对塔中大沙漠区潜水面稳定这一特点，讨论了野外低速带调查仅确定潜水面的埋深的可行性，这样可以大大降低调查点密度。

Small refraction and upholes are the main technologies for low-velocity zone investigation in the massive deserts of middle Tarim basin, which aim at obtaining the near-surface velocity model for the source depth design and datum statics calculation. Source depth of massive deserts in middle Tarim basin is generally designed 1 to 3 meters under the water table and it is easy to obtain the burial depth of water table by small refraction and uphole. However, the calculation of field statics should obtain the detailed velocity distribution of all layers above substitution velocity (2000 m/s). For the effect of acquisition density and investigation depth, the field statics obtained by small refraction and uphole exist a big error and the stacking profiles after field statics has a long wavelength static problem. This problem was effectively solved by using nonlinear first break tomography inversion static method to take the place of the small refraction and uphole. Finally, aimed at the steady water table in massive deserts of middle Tarim basin, the feasibility of only identifying the depth of water table in the area with low-velocity zone was discussed, indicating that it can largely decrease the density of investigation points.