准噶尔盆地腹部二次三维地震勘探主要技术与效果(为庆祝克拉玛依油田勘探开发50周年而作)

20世纪90年代在准噶尔盆地开展了以大面元区带三维为主的一次三维地震勘探,旨在寻找大中型构造油气藏,成效显著.进入新世纪以来,随着勘探目标向岩性-地层型油气藏转换,一次三维精度不足的缺陷逐渐显现,为此,在地质评价非常高的一次三维覆盖区开展了二次三维地震勘探.二次三维地震勘探突出应用了5项技术措施,即宽方位角观测与束间耦合,常规面元或小面元采集,地表相对潮湿季节施工,根据表层条件优选激发参数和应用中高频检波器接受与炮检联合组合.在厚沙漠区,二次三维资料主频比一次三维高15～20 Hz,达到45～50 Hz,其信噪比、保真度也有很大提高.对小断裂、不整合面、尖灭点和砂体的地震反射成像清晰度明显提高,岩性圈闭识别能力增强.

Results and Technologies of Second-Time 3D Seismic Prospecting in Hinterland of Junggar Basin

The first-time 3D seismic exploration activities have been made since 1990's, which were dominated by regional 3D seismic with large bin size, aiming at finding out large- to medium-sized structural traps and reservoirs, and lots of significant achievements were made. With the advent of new century, the insufficient precision of the first-time 3D seismic activities appeared gradually as the focus of prospecting toward lithologic-stratigraphic reservoirs. So it is necessary to perform the second-time 3D seismic activities in highly evaluat- ed areas covered with 3D seismic survey before. And 5 different technologies are applied such as wide-azimuth geometry and swath cou- pling, acquisition with normal or small bin size, seasonal or relatively wet surface acquisition, selection of source parameters by surface condition and application of medium-high frequency geophone and source-geophone array to receive seismic wave. In thick desert area, the main frequency of 45-50 Hz is used, about 15-20 Hz higher than the first-time 3D data, and signal to noise ratio and fidelity are sig- nificantly improved. As a result, the seismic reflection image definitions of small faults, unconformity surface, pinchout point and sand- body are also improved matkedly and the recognition capability of the lithologic traps are intensified in terms of geologic effect.