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经过前期勘探 ,已证实柴达木盆地中部存在浅层生物成因天然气 ,并发现了 6个浅层天然气田 ,即涩北一号、涩北二号、台南、台吉乃尔、驼峰山和盐湖。在过气田的时间地震剖面上存在典型的“气烟囱”效应 ,即由于天然气藏的气体向上运移及逸出 ,由于地震波能量被吸收而在时间地震剖面上出现的下拉、低频、深层成像差等现象。叠前深度偏移 (PSDM)是石油勘探家行之有效的一种解释性方法 ,它能够改善成像质量 ,提高信噪比 ,使深度剖面具更高的解释可信度。成像质量的提高是通过建立精确的速度模型而实现的。建立了精确的速度模型 ,就能够准确地归位目标层反射能量 ,提高信噪比 ,从而达到消除“气烟囱”效应的目的。在涩北区块 (柴达木盆地 ) ,应用以上方法得到的深度地震剖面消除了时间剖面伴有的速度效应 ,使得解释人员能更好地解释区块的构造背景 ,并应用Geosec2D软件对涩北一号和盐湖构造进行构造形成期分析。图 8参 7
After the previous exploration, it has been confirmed that shallow biogenic natural gas exists in the central Qaidam basin and six shallow gas fields have been discovered, namely Sebei No.1, Sebei II, Tainan, Tajinel, Hump Mountain and Salt Lake. There is a typical “chimney” effect on the time-seismic profile of the over gas field. Because of the upward migration and escape of gases in the gas reservoir, the pull-down, low frequency and deep imaging aberrations on the time-seismic profile due to the absorption of seismic energy And so on. Prestack depth migration (PSDM) is an effective interpretation method for oil prospectors, which can improve the imaging quality, improve the signal-to-noise ratio and make the depth profile more credible. The improvement of imaging quality is achieved by establishing accurate velocity models. The accurate velocity model is established to accurately locate the reflection energy of the target layer and improve the signal to noise ratio so as to eliminate the effect of “gas chimney”. In the Sebei block (Qaidam basin), the depth seismic profile obtained by applying the above method eliminates the velocity effect accompanying the time profile, so that the interpreter can better explain the tectonic setting of the block and apply Geosec2D software to the astringent North No. 1 and Salt Lake tectonic formation period analysis. Figure 8 Reference 7