三湖地区真假含气地震异常的识别与处理技术

Identification and elimination of non-gas-related seismic anomalies in the Sanhu area,Qaidam Basin

柴达木盆地三湖地区地震剖面上的"低频、同相轴下拉"现象是寻找气藏的有效手段。但是随着勘探的深入,发现地震反射异常现象并不都是由于地层含气引起的,一些特殊的地表条件(表层结构异常)也会造成类似的异常现象,致使一些探井钻探失利。在近两年的该区高精度二维地震勘探中,通过针对性的表层调查方法和对近地表结构的精细解剖,弄清楚了地震反射异常与表层结构的对应关系,对表层结构引起的地震异常有了较深刻的认识;通过分析总结,提出了用反射时间法来甄别表层异常与地下含气异常;在此基础上,通过高精度折射静校正处理技术消除了这些由于表层结构异常变化带来的地震资料异常。这些技术措施的实施,为三湖地区地震资料真假异常的识别提供了比较实用的方法,在实际的生产应用中见到了较好的效果。

Seismic anomaly of 'low frequency and event down-pulling' was previously believed to be indicators of gas reservoirs on seismic section in the Sanhu area,Qaidam Basin.However,along with the deepening of exploration,it is discovered that not all the seismic anomalies are caused by gas in reservoirs and some surface structures can also induce similar anomalies,leading to the failure of some exploratory wells.During the high-resolution 2D seismic exploration in recent two years,we have discovered the relationship between this kind of anomaly and surface structures based on a detailed analysis of surface structures.A reflection time method is presented for differentiating seismic anomalies caused by surface structures and those by subsurface gas reservoirs.The high-resolution refraction static correction technique is used to eliminate the anomalies caused by surface structures.These methods are practical for the differentiation of non-gas-related and gas-related seismic anomalies.