Title

Effects of excitation depth and geophone coupling on near-surface Q value estimation

单位

(1.中国石油集团东方地球物理勘探有限责任公司,天津300280;2.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;3.非常规油气湖北省协同创新中心,湖北武汉430100;4.成都信息工程大学气象信息与信号处理四川省高校重点实验室,四川成都610225)

Organization

(1.BGP Inc.,CNPC,Tianjin 300280,China;2.Key Laboratory of Exploration Technology for Oil and Gas Resources of Ministry of Education,Yangtze University,Wuhan 430100,China;3.Hubei Cooperative Innovation Center of Unconventional Oil and Gas,Wuhan 430100,China;4.Meteorological Information and Signal Processing Key Laboratory of Sichuan Higher Education Institutes of Chengdu University of Information Technology,Chengdu 610225,China)

摘要

激发深度和检波器耦合效应会影响地震信号的频谱特征。基于实际微测井资料研究地震波主频变化特征可知,不同深度激发获取的地震子波主频相差近55 Hz,检波器耦合效应使地震子波严重缺失低频信息,且高频部分出现类似“陷波”现象。基于地表一致性理论,定量地模拟了不同激发深度以及不同检波器耦合条件对近地表Q值估算结果的影响,结果表明,激发深度差异与检波器耦合差异会大幅度降低近地表Q值估算的精度。在大港ZY地区实际双井微测井数据采集过程中,通过选取合适的井下检波器接收深度以及制作井下助插器等方法保障井下检波器耦合效果,并采用共激发点资料消除激发条件差异带来的影响,提高了近地表Q值的估算精度。

Abstract

Excitation depth and geophone coupling strongly affect the frequency spectrum of seismic data.Uphole survey data analysis indicates that the main frequency of the seismic wavelet excited from the deeper layer is higher than is that from the shallow layer.The wavelet spectrum shows a serious lack of the low frequency component,and high frequency shows the notch phenomenon because of poor geophone coupling.Based on the surface consistency theory,seismic signals under different excitation depths and geophone coupling conditions were analyzed quantitatively.It was found that the Q factor estimation accuracy decreased because of the seismic wavelet differences resulting from the different excitation depths and geophone coupling conditions.During the actual data acquisition of a double-hole uphole survey in the ZY area of Dagang,a reasonable depth was chosen where the geophone was laid over the water table,and a special instrument was utilized to ensure the geophone coupling state in order to improve the estimation accuracy of the near-surface Q values.

关键词：

激发深度; 检波器耦合; 近地表; Q值估算; 吸收衰减;

Keywords:

excitation depth,; geophone coupling,; near-surface,; Q value estimation,; absorption attenuation;

基金项目

成都信息工程大学气象信息与信号处理四川省高校重点实验室开放课题资助(QXXCSYS201701)和油气资源与勘探技术教育部重点实验室(长江大学)开放基金(K2016-11)共同资助。

DOI

10.3969/j.issn.1000-1441.2018.05.006

激发深度和检波器耦合对近地表Q值估算的影响分析