含平行裂缝储层中地震波频散、衰减及频变各向异性

Seismic dispersion, attenuation, and frequency-dependent anisotropy in reservoirs with aligned fractures

裂缝厚度(张开度)对裂缝储层有效渗透率等起关键作用因而探测裂缝厚度对裂缝储层的勘探开发具有重要意义。针对此,该文主要介绍地震波在含平行裂缝储层中的频散、衰减及频变各向异性特征,及其与裂缝厚度的关系。重点探讨了流体运动与散射两种主要机制,并介绍了最新的理论模型研究进展。研究表明,裂缝厚度对流体运动与散射机制均会产生重大影响,主要影响频率范围为流体运动的高频区域和散射的低频区域。该频率范围常在地震频带内,故在实际地震勘探中应考虑裂缝厚度的影响,其同时为地震探测裂缝厚度提供了理论基础。最后,还探讨了流体运动与散射机制的耦合作用,并给出了相应的理论模型。结果表明,两种机制相互耦合时,地震波的频散衰减特征会发生明显变化,应予以考虑。

Fracture thickness(aperture)has significant influence on the effective permeability of the fractured reservoirs.Therefore,it is of great importance to detect the fracture thickness in the exploration and development of fractured reservoirs.For this purpose,this paper primarily introduces the dispersion,attenuation,and frequency-dependent anisotropy of seismic waves in reservoirs with aligned fractures,as well as their relations with fracture thickness.Two important mechanisms including wave-induced fluid flow(WIFF)and scattering are investigated and the recent developments on the related theoretical models are introduced.It is found that the fracture thickness has significant influence on both WIFF and scattering.The primary influenced frequency regimes are the high frequency regime of WIFF and low frequency regime of scattering.These frequency regimes usually fall into the seismic frequency band and hence it is essential to consider the effects of fracture thickness in the seismic exploration.This in turn provides the theoretical basis for the seismic detection of the fracture thickness.Finally,the coupling between WIFF and scattering is also investigated and the corresponding model is given.The results show that the features of the seismic dispersion and attenuation will become notably different when the coupling occurs.Hence,it needs to be considered.