薄互层AVO响应特征分析

1.西南石油大学 地球科学与技术学院,四川 成都 610500; 2.中国石油川庆钻探工程公司地球物理勘探公司,四川 成都 610213; 3.中国石油长庆油田公司,陕西 西安 710018

薄互层; AVO; 正演模拟; 截距; 梯度

Analysis of seismic AVO response for thin inter-layer reservoir
SHE Yu-wei1,ZHU Shi-jun1,ZHU Peng-yu2,DANG Zhou-tao3,TANG Xu-lei2,YANG Wei-lei3,HU Gui-lin3

(1.School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China; 2.Geophysical Prospecting Company of Chuanqing Drilling Engineering Co.,Ltd.,CNPC,Chengdu 610213,China; 3.Changqing Oilfield Company,Petro China,Xi'an 710018,China)

thin interbedding; AVO; numerical simulation; intercept; gradient

DOI: 10.13800/j.cnki.xakjdxxb.2014.0618

备注

行业公认技术作为流体检测的重要工具,近年来,在单一薄层AVO响应特征方面取得了许多重要成果,这些成果为地层中单一薄层流体检测定性解释奠定了良好的基础,但作为地层中沉积更为普遍更的地质结构——砂泥岩薄互层,研究相对较少。文中首先对声学介质和弹性介质条件下的薄互层AVO响应进行研究,其次利用交错差分弹性波动方程对韵律型含气等厚薄互层进行数值模拟,研究薄层数和单层厚度对薄互层AVO响应的影响,最后利用梯度的变化特征,对薄互层层进行分类,研究其截距梯度交会(P-G)属性。结果 表明,薄互层的AVO响应在声学介质情况下会出现假亮点,在弹性介质中进行数值模拟更加合理。在弹性介质中与单层薄砂岩AVO响应进行比较,发现薄互层单层厚度小于1/8波长时,薄互层对顶面AVO效应起到加强的作用; 而当薄互层单层厚度大于1/8波长小于1/4波长时,AVO效应较薄层情况减弱。随着薄互层单层厚度的增加,P-G值发生明显的变化。因此可以根据工区薄互层单层厚度和层数确定出薄互层发育的P-G属性的分布范围,从而指导储层预测,为勘探开发提供依据。

Amplitude versus offset(AVO)as an important tool for seismic fluid detection,has achieved many important results on the aspect of a single thin-bed AVO responses in recent years and those achievements would be a good foundation for the qualitative interpretation of a single thin-bed.However,the study of more common geological structures sand-shale thin inter-layer series are relatively less.In this study,the media for thin inter-layer AVO modeling in acoustic and elastic regime are compared firstly.Then staggered difference elastic wave equation is adopted for the numerical simulation of isopachous thin interbedding,aiming at analyzing the influence of the single layer thickness and number of thin layers.At last,the classification of thin interbedding based on gradient is taken for the further study of P-G attributes.The result shows that the simulation in elastic media is more suitable for thin interbedding,due to fake highlights appears at the modeling in acoustic regime.Compareing thin interbedding AVO responses with a single sand thin bed in elastic media find that if the single layer thickness of thin inter-layer is less than 1/8 wavelength,thin interbedding strengthen AVO effects of the top surface; while the single layer thickness is between 1/8 and 1/4 wavelength,AVO effects of thin inter-layer is weaker than a single thin bed.Finally,as the increase of the single layer thickness of thin interbedding,P-G properties is changed obviously.Therefore,according to the single layer thickness and number of thin layers in work area,the P-G attributes distribution of thin inter-layer reservoir is determined which is helpful to guide reservoir prediction and provide the basis for exploration and development.