地震勘探中的各向异性影响问题研究

Studies on the influence of anisotropy in seismic exploration

各向同性介质的常规地震成像技术和叠前时间/深度偏移地震成像技术已被广泛应用于构造解释和岩性识别,并获得了一定的应用效果,但其地震分辨率显然还难以满足薄储层识别和解决油田开发问题的需要。为此,本文基于零井源距VSP、8方向的WalkawayVSP、3DVSP和全方位三维地面地震的联合地震采集数据,针对沉积环境相对稳定的薄储层和裂缝性储层,探讨了VTI、HTI介质和剩余静校正对地震勘探的影响。研究结果认为,对于沉积环境相对稳定的薄储层和裂缝性储层,VTI介质是影响地震成像分辨率的主要因素,在3000m炮检距时会引起约100ms的时差;而HTI介质(含非均匀速度和构造倾角)的方位影响通常小于±20ms,但也会影响地震成像的分辨率。同时,HTI介质的相对空间变化信息的求解有助于裂缝性储层的预测。此外,VTI和HTI介质会直接影响基于地表一致性理论的剩余静校正的求解能力。因此,对于沉积环境相对稳定的薄储层和裂缝性储层勘探而言,充分考虑VTI和HTI介质的影响,将能有效提高地震勘探的分辨率和储层预测能力。

Routine seismic imaging technique and pre-stack time/depth migration imaging technique in isotropic media have been widely applied in structure exploration and lithology exploration,great application effects have been achieved.However the seismic resolution still can not meet the need of exploration for thin reservoir and oilfield development.Based on the data gathered by integrated seismic of zero-offset VSP,8-direction Walkaway VSP,3D VSP and full azimuth 3D ground seismic,the influence of VTI medium,HTI medium and residual static correction to seismic exploration were discussed for thin reservoir and fractured reservoir in stable deposition environment.For the reservoir and fractured reservoir in stable deposition environment the study results show that the VTI medium is the main influence factor for seismic imaging resolution,it could cause 100 ms time difference within 3000M offset,for HTI medium(including non-uniform velocity and structure dip) the orientation influence is generally less than ±20 ms,but it could also affects the resolution of seismic imaging.Meantime the solution of HTI medium relative space information could help to predict fractured reservoir.In addition VTI and HTI media could directly affect the solution accuracy of residual static correction,which is based on surface consistency theory.Therefore for thin reservoir and fractured reservoir in stable deposition environment,fully considering the influence of VTI and HTI media will help us raise seismic exploration resolution and reservoir prediction ability.