Title

Research on reservoir thickness influence on seismic reflections

作者

秦喜林杨飞刘媛媛

Authors

Xilin QIN Fei YANG Yuanyuan LIU

单位

1. 油气资源与勘探技术教育部重点实验室(长江大学), 湖北武汉 430100 2. 中国石油物探重点实验室, 长江大学, 湖北武汉 430100 3. 中国石化江汉油田勘探开发研究院, 湖北武汉 430070

Organization

1. Key Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, Yangtze University, Wuhan 430100, China 2. Key Laboratory of Geophysical Exploration of CNPC, Yangtze University, Wuhan 430100, China 3. Exploration and Development Research Institute, Jianghan Oilfield, Sinopec, Wuhan 430070, China

摘要

薄储层的衰减机制主要包含固有衰减和散射衰减, 在地震频带范围内, 散射衰减主要表现为薄层调谐效应, 固有衰减主要由介质的黏弹性导致。为了厘清储层厚度对地震波的影响规律, 应用广义传播矩阵正演算法对比分析了各向同性楔状模型和各向异性楔状模型地震波振幅随偏移距的变化特征, 然后利用改进的反演谱分解技术和频变AVO反演方法提取模型正演数据的频散属性, 最后分析储层厚度对地震波频散特征的影响规律。研究结果表明, 固有衰减会明显减小储层的反射振幅, 而散射衰减使储层反射振幅随着厚度先增加后减小; 地震波频散随着地层厚度的增加呈"M"型变化, 其两个极大值分别出现在λ/20和λ/2附近(λ为波长), 极小值对应厚度为λ/4;当储层厚度小于λ/4时, 散射衰减对反射振幅和频散的影响明显强于固有衰减。

Abstract

Wave attenuation across a thin reservoir mainly includes intrinsic attenuation and scattering attenuation.The former is caused by the viscoelasticity of media within seismic frequency band, and the latter manifests as tuning effect in a thin layer.In order to clarify the influence of reservoir thickness on seismic waves, we use the generalized propagation matrix to perform forward modeling of amplitude variation with offset for an isotropic and an anisotropic wedge model, and then extract the dispersion attribute from modelled data using a modified inversion spectral decomposition and frequency-dependent AVO inversion to investigate the impact of reservoir thickness on seismic-wave dispersion.The results indicate that intrinsic attenuation significantly reduces the reflection amplitude from the reservoir, while scattering attenuation causes reflection amplitude to first increase and then decrease with thickness.Seismic-wave dispersion shows a M-shaped curve as reservoir thickness increases, on which two maxima appear at the thicknesses around 1/20 wavelength and 1/2 wavelength, respectively, and the minimum at 1/4 wavelength.When reservoir thickness is less than 1/4 wavelength, scattering attenuation shows a stronger influence on reflection amplitude and dispersion than intrinsic attenuation.

关键词：

衰减; 调谐效应; 速度频散; 各向异性; 薄储层;

Keywords:

attenuation; tuning effect; velocity dispersion; anisotropy; thin reservoir;

基金项目

国家自然科学基金联合项目(U20A2092);油气资源与勘探技术教育部重点实验室(长江大学)第八批开放基金(K2021-04)

DOI

10.12431/issn.1000-1441.2024.63.03.010

薄储层厚度对地震反射波的影响规律研究