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3-D地震勘探技术作为获得详细地下资料的方法,在工业上已得到了认可。但3-D地震数据采集的成本现在是将来也永远是相当高的。因此选择正确的观测系统显得特别重要。直到目前,还没有一套完整的理论能够告诉我们是什么构成一个优秀的3-D观测系统,这样一个系统如何去设计。本文提出的3-D对称采样理论的目的是填补这项空白,可以作为3-D观测系统设计和分析的坚实基础。从80代起,有关设计2-D勘探的理论和方法就开始发展起来。Anstey提出了叠加组合的方法,Ongkiehong和Askin提出了自动采集技术,Vermeer提出了对称采样技术。在本文中,2-D观测系统的对称采样理论扩展到目前正在使用的最重要的3-D观测系统中。在3-D对称采样中,观测系统的空间特征是基本要素,空间特征重要是因为大部分地震处理程序是在把相邻道合并到新输出道上的某个空间域进行的,而且解释人员必须把3-D地震数据体的空间特征成图。一段时间以来,曾出现了各式各样的测量观测系统来进行3-D地震数据采集。所有这些观测系统都是与5-D叠前波场(4个空间坐标轴描述了震源和检波点的位置,第5个坐标轴表示了旅行时)的全采样有关的折衷方法。因此得出,大多数观测系统可以被认为是5-D波场的3-D子集的集合,每一个子集仅有两个变化的空间坐标。每个子集的地震道的空间分布变化是缓慢而有规律的。该性质使3-D勘探具有空间连续性,如果子集的采样合适,并可延伸到最大范围时,就可以充分利用空间连续性。 2-D对称采样标准——等炮距和接收距及等炮检组合同样也用于3-D对称采样,但对不同的观测系统要附加不同的标准。正交观测系统(平行炮线与平行接收线正交的观测系统)的附加标准就是为了保证最大横测线炮检距等于最大纵测线炮检距。 3-D对称采样观测系统简化了3-D观测系统的设计。一张简单的地球物理要求清单(空间连续性、分辨率、浅目的层和深目的层的可绘图性、信噪比)限制了勘探参数的选取。在以上所考虑的因素中,也已隐含地照顾到了炮检距和方位角分布。在野外具体实施时,要求认真计划以防失去空间连续性。
The 3-D seismic exploration technology has been industrially recognized as a method of obtaining detailed underground information. But the cost of 3-D seismic data acquisition is now and will always be quite high. So choosing the right observing system is particularly important. Until now, no complete theory has been able to tell us what constitutes an excellent 3-D observation system and how such a system can be designed. The purpose of the proposed 3-D symmetric sampling theory is to fill this gap and serve as a solid foundation for the design and analysis of 3-D observation systems. Beginning in the 80s, theories and methods of designing 2-D exploration began to develop. Anstey proposed a superposition method, Ongkiehong and Askin proposed automatic acquisition techniques, and Vermeer proposed symmetric sampling techniques. In this paper, the symmetric sampling theory of 2-D observing systems is extended to the most important 3-D observing systems currently in use. In 3-D symmetric sampling, the spatial features of the observing system are the basic elements. The spatial features are important because most of the seismic processing is performed in one of the spatial domains that merge adjacent tracks into the new outgoing track, and the interpreter must The spatial characteristics of 3-D seismic data are mapped. For some time now, a wide range of measurement and observation systems have emerged for 3-D seismic data acquisition. All of these observational systems are eclectic methods related to the full sampling of 5-D prestack wavefields (the 4 spatial axes describe the source and detector locations and the 5th axis indicates travel). It follows that most observing systems can be considered as a set of 3-D subsets of 5-D wavefields with only two varying spatial coordinates for each subset. The spatial distribution of the traces of each subset varies slowly and regularly. This property allows 3-D exploration to have spatial continuity, making it possible to make full use of spatial continuity if the subsets are properly sampled and extended to the maximum. The 2-D Symmetric Sampling Standard - Equal Gun Distance and Receiver Distance and other gun combinations are also used for 3-D symmetric sampling, but with different standards for different observing systems. An additional standard for the Orthogonal Observation System (Orthogonal Observation System for Parallel Gun and Parallel Receiving Lines) is to ensure that the maximum cross-line offset equals the maximum in-line offset. The 3-D symmetric sampling observation system simplifies the design of the 3-D observation system. A simple list of geophysical requirements (spatial continuity, resolution, pliability of shallow and deep layers, signal-to-noise ratio) limits the selection of exploration parameters. Among the factors considered above, the offset and azimuth distribution have also been taken care of implicitly. When implemented in the field, careful planning is required to prevent loss of spatial continuity.