裂缝性气藏转换波3D3C地震采集观测系统优选

Optimization of converted wave 3D3C layout for fractured reservoir

川西坳陷深层须家河组气藏具有埋藏深、岩性致密、非均质性强、储层类型多样、气水关系复杂等特点,采用常规油气藏地震勘探技术难以取得很好的效果。转换波三维三分量(3D3C)勘探综合了纵波勘探和转换波勘探的优势,对于解决川西深层致密裂缝性储层的裂缝检测及含气性预测问题具有良好的应用前景。为此,针对深层气藏特点及裂缝检测的需要,对接收线距、束间滚动距、宽窄方位角、观测系统类型及覆盖次数等观测系统参数进行了分析论证,认为斜交方式、小接收线距、小滚动距、全方位、高覆盖次数等是决定采集数据随方位角和偏移距分布均匀的主要因素,可以更好地满足纵横波方位各向异性分析及横波分裂裂缝检测要求。设计了3个斜交砖墙式观测系统方案,并结合XC地区3D3C转换波勘探观测系统分析进行了优选。

The Upper Triassic reservoir of Xujiahe Formation is deeply buried, tight, and heterogeneous in the west of Sichuan. Reservoir types are varied. Therefore conventional seismic survey often fails to yield desired results. It has been proved promising to solve the problem of detection of fractures and hydrocarbon potentials for fractured tight sand reservoir in the west of Sichuan by taking the advantages of both P-and converted-wave exploration. We designed and tested the layout of 3D3C seismic acquisition in terms of receiving line spacing, swath rollover distance, wide and narrow azimuth, fold, and array, and concluded that key factors to get symmetrical distribution of offset and azimuth are obliquely crossing layout with small receiving line spacing, small rollover distance, full azimuth, and high fold. Three candidate patterns of oblique brick layouts have been worked out. The optimized one is singled out for 3D3C survey in XC area.