全波场地震采集

Full-wave field seismic acquisition

尽管高精度三维地震采集取得了巨大的成功,但面对更复杂地质体时,探索能同时进行连续界面反射及随机介质散射的全波场地震采集的方法依然十分重要。地震采集面临两大困难,一个是不存在同时满足大倾角界面反射波与小尺度介质散射波的单一观测系统,即现有野外排列并不能对散射波充分采样;另一个是面对小尺度介质产生的地震波散射,不能同时满足横向分辨率与最小介质尺度对空间采样的要求,认为对小尺度介质进行充分采样无效。在引入量子力学概念后,地下非均质体与地震波的传播构成量子系统,散射波被视为概率波,空间采样密度便不再受限制。全波场地震采集是均衡获取多态式地震波的过程,由于不能靠稀疏、规则的采样方式获取,概率波采集需要满足遍历性,宜采用共中心点道集离散化技术,基于多观测系统设计和炮道密度控制的细分面元方法实现。考虑到地震散射波信号弱,存在局域性和不确定性,应选择小面元、小道距、小偏移距、近偏高覆盖和炮点与检波点局部随机布设等采集参数。全波场地震采集方式灵活,支持同期、多期镶嵌或井场连续地震采集,有效信号更丰富,背景噪声更低,地震波信号的频率范围更宽,而且经济上可以接受且物理可实现。

High-precision 3D seismic acquisition has achieved considerable success.However,for complex geological bodies,it is important to develop full-wave field seismic acquisition methods that can adapt to both continuous interface reflection and random medium scattering.There are two difficulties in seismic acquisition.First,there is no single seismic layout that satisfies both the reflection of large dip interfaces and the scattering of small-scale media;thus,the existing field arrays cannot adequately sample the scattered waves.Second,for the scattering of seismic waves generated by small-scale media,existing observation systems cannot satisfy both the lateral resolution and spatial sampling requirements of the minimum medium size;thus,it is impossible to completely sample small-scale media.According to the concept of quantum mechanics,the propagation of underground heterogeneous bodies and seismic waves is considered to constitute a quantum system,and scattered waves are considered probability waves,so that the spatial sampling density is no longer limited.Full-wave field seismic acquisition is a process of obtaining multi-state seismic waves in a balanced manner.Because probability waves cannot be obtained through sparse and regular sampling,probability-wave acquisition must satisfy the ergodicity requirement.It is advisable to adopt common-midpoint gather discretization technology,which is achieved through multiple observation system design and bin subdivision controlled by the trace density.Owing to the weak seismic scattered wave signal and the characteristics of localization and uncertainty,acquisition parameters should be selected,such as a small bin,a small trace spacing,a small spread,high coverage at near-offset,and a local random layout of the shot and receiver.The full-wave field seismic acquisition method is more flexible and can support simultaneous acquisition,multi-phase embedded acquisition,or well site continuous acquisition.The data have richer effective signals,less background noise,and wider frequency bands.This technology is economically acceptable and physically achievable.