山地复杂构造倒转背斜地震剖面反射特征及油气成藏分析

Seismic reflection features and analysis of hydrocarbon accumulation of reversed anticlines in complicated mountainous areas

中国西部山地复杂构造的倒转背斜是重要的含油气构造类型之一。高陡复杂构造区许多失利井,与倒转背斜的地质特点及其地震剖面反射特征认识不足有关。依据地面地质、钻井和测井资料建立倒转背斜模式,采用模型正演和偏移技术分析不同类型倒转背斜的地震响应特征,建立在地震剖面上识别倒转背斜的模式和方法,有助于在地震剖面上查明倒转背斜形态。具有较高信噪比的山地复杂构造,叠前深度偏移剖面能很好地反映出倒转背斜形态。倒转背斜正常翼地层剥蚀程度低,埋藏深度适中,可成为良好的油气圈闭;倒转翼地层陡倾,断块发育,油气成藏条件差,倒转翼下方潜伏背斜保存条件好,是油气聚集有利场所,油气勘探效果良好。

The reversed anticline is one of the most important hydrocarbon-bearing structures in the mountainous area in western China. Many wells drilled in the steep and complicated structures failed, largely due to insufficient understanding on the geological and seismic re什ection characteristics of the reversed anticlines. Based on surface geology, drilling and well logging data, different modes of reversed anticlines were established, then the seismic response features of different types of reversed anticlines were analyzed through forward modeling and migration, and finally the reversed anticlines were recognized based on seismic sections. This method is helpful to identifying the forms of the reversed anticlines. For the complicated mountainous structures with seismic data with high SNR, pre-stack depth migration sections can clearly show the forms of the reversed anticlines. If the normal limb of the reversed anticline is less denuded and moderately buried, it may be a good hydrocarbon trap. If the limb is steep and faults are developed, the conditions for hydrocarbon accumulation may be poor. The buried anticlines beneath the reversed limb have good preservation conditions favorable for hydrocarbon accumulation, so they are promising targets for hydrocarbon exploration.