先验信息约束层析成像静校正技术在柴西南地区的应用

在柴达木盆地西部南区,针对不同的地质目标采集了多块三维地震资料,对于该地区进一步的油气勘探开发,需要整体认识该区域的地质特征和沉积相,为此在该区开展了三维地震资料连片处理研究。柴西南地区近地表结构复杂,岩性多变,地表高差达600 m,低、降速层厚度变化大(4～200 m),连片处理中静校正问题突出。在对各种静校正方法适应性分析的基础上,提出了先验信息约束层析成像静校正技术,阐述了该方法的基本原理和实现步骤。在方法实现时,区块之间的初至时差采用相关法予以消除,初始速度模型采用相控处理的小折射和微测井资料来建立,并将该模型作为初至波非线性层析反演的约束条件,建立了准确的近地表速度模型,计算全区的静校正量。应用效果分析表明,先验信息约束层析成像静校正技术可以较好地解决复杂地区三维地震资料连片处理中的静校正问题。

Application of priori information constraint tomography static correction technique in the south of Western Qaidam basin

In the south of western Chaidamu Basin,many blocks of 3-D seismic data with different geological targets have been acquired.The further exploration and production requires research on the overall geological features and sedimentary facies.Therefore,we carried out 3-D multi-surveys merged processing at the area.In this area,the near surface structure is complex,the lithology changes fast,the surface elevation difference reaches to 600m,the thickness of low-velocity zone is from 4 to 200 m,so the statics problem is serious in merged processing.After analyzing the adaptability of different statics methods,we proposed tomography statics constrained by priori information,and presented its basic theory and realization steps.In practical application of the method,correlation method is used to eliminate the first-arrival time difference between blocks,the initial velocity model is built with the shallow refraction and uphole data after phase-control processing,then first-arrival wave non-linear tomography inversion is carried out constrained by this initial model,finally,an accurate near-surface velocity model is built,and the static correction value can be calculated for the whole area.The application analysis indicates that tomography statics constrained by priori information can well solve the statics problem in 3-D multi-surveys merged processing in the area with complex near-surface conditions.