川东高陡构造的深度偏移应用研究

APPLICATION RESEARCH ON DEPTH MIGRATION OF THE STEEPLY-FOLDED STRUCTURE IN EAST SICHUAN

川东高陡构造由于层速度在横向上的剧变 ,通常的时间偏移处理不能使反射正确归位 ,得不到正确的构造形态和高点位置。文章针对川东陡构造的地质及地球物理特征 ,对时间偏移 ,Geodepth软件叠前和叠后波动方程深度偏移 ,以及叠后射线变速深度偏移等方法做适用性研究后发现 :对于川东这种地表高差大、地腹构造形态复杂导致层速度变化剧烈的地区 ,深度偏移明显比时间偏移校正能力强 ,所得到的构造形态和高点位置更准确 ,并且在速度校正方面叠前比叠后深度偏移好。但是 ,叠前与叠后深度偏移在成像上相当 ,在运算速度上后者比前者快 10倍。由此 ,总结出了适合川东高陡构造深度偏移的方法及一套叠前、叠后深度偏移处理流程。通过对温泉井、沙坪场、黄泥堂、南门场等构造的实际应用 ,获得了良好的钻探符合率及钻探成功率 ,这表明深度偏移具有明显效果。

Owing to the extreme lateral change of the interval velocity of the steeply-folded structure in east Sichuan, the normal time migration process makes reflection position not correct and distorts structural shape. Aimed at the geologyical and geophysical charateristics of the steeply-folded structure in east Sichuan, an application research is carried out for time migration, prestack & poststack wave equation depth migration of Geodepth softeware and poststack raypath variant velocity depth migration etc. The result shows that the depth migrations are of higher rectifiable ability than time migration; the structural shape and top position obtained by the former are more accurate; the prestack depth migration is more favorable than the post one in the aspect of velocity rectification for the area with extreme variant elevation and violent interval velocity change caused by the complicated underground structure. The image of the prestack depth migration corresponds to the poststack depth migration, but the calculating speed of the latter is 10 times of the former. In this paper, a method and a set of precessing flows of prestake and poststack depth migration are summaried to match depth migration of this region. Through the actual operation of the structures such as Wenquanjing, Shapingchang, Huangnitang and Nanmenchang etc., favorable drilling coincidence rate and success rate are achived.