海上拖缆时移地震采集设计实例

两期海上拖缆地震数据采集时海况等因素的不同,会导致时移地震数据中激发点、接收点和拖缆羽角的差异。特别是在拖缆地震方位角较窄和海上钻井平台位置变化时,这些差异会严重影响时移地震的可重复性。在实施南海M油田时移地震项目过程中,对于前期较差地震观测数据(缆数少、激发航线复杂、拖缆羽角大),二期时移地震采集应采用更多的缆数、较密和较直的激发航线、较小拖缆羽角进行观测; 时移地震数据处理中,在满足激发点误差与接收点误差之和不超过100m的条件下,通过时移地震数据重构、相对保持拼接处理和适当的互均衡处理可获得高于99%可重复的时移地震数据,能满足储层沉积解释和剩余油气预测的要求。

Towed streamer time lapse seismic survey design: a case study

Environment (obstacles, weather, tide and etc.) differences often cause differences of source and receiver positions and feathering angles in offshore streamer time lapse seismic. Especially narrow azimuth survey and platform positions shifted in an area will result in non-repeatable features of time lapse seismic. For towed streamer time lapse seismic project in the oilfield M in South China Sea, the baseline is a 4-streamer survey with complicated sail line and big feathering angle. For the monitor survey, 10 streamers with dense and straight sail line (100m separation instead of 200 m for baseline) and smaller feathering angle are adopted. In the data processing stage when source and receiver position difference between baseline and monitor surveys is less than 100m, the trace pairs with the minimum positioning error is reconstructed from redundant monitor seismic data. And relative amplitude preserved processing of the two vintage data as well as the cross-equalization finally produce the 4D seismic result with 99% repeatability, which satisfy the requirement of reservoir study and remaining oil predication.