摘要
井中分布式光纤声波传感(DAS)系统作为新一代井中地震观测装备,与传统的井中三分量数字采集系统相比,具有施工安全、高效,一次激发即可实现全井段观测的优点。DAS系统具有传、感一体的特点,因此在井中光缆悬挂观测时无法实现光缆的完全推靠以及井口段光缆张力的有效减少,这导致地震资料采集时会产生较强的缆波和耦合干扰,从而影响地震资料的信噪比。从地震波的传播规律出发,分析了DAS井中观测干扰波的产生过程和特征,明确了DAS系统缆波干扰和“弹簧波”干扰是由波到达光缆时沿着光缆传播而形成。采用随机中值滤波技术压制缆波干扰以及模拟正反演法压制“弹簧波”干扰,提高了地震采集资料的信噪比。该方法在实际地震资料应用的结果表明:DAS干扰波的分析合理,噪声压制效果明显,去噪后的DAS数据能够获得较好的井中地震成像结果。
Compared with a traditional three-component digital acquisition system,the distributed fiber acoustic sensing(DAS)system is safer and highly efficient during operation.In fact,using a single shot,the entire well section can be scanned.This new-generation technology can meet the current needs of in-borehole data acquisition.However,since DAS systems are characterized by integrated transmission and sensing,it is not possible to fully stretch the optical cable,and at the same time,minimize the tension at the wellhead during in-borehole operation.This results in a strong interference that decreases the signal-to-noise ratio of the data.Exploiting the propagation law of seismic waves,this study analyzes the process of generation of interference waves in the DAS system,and their wavefield characteristics.The DAS system records the same wavefield as that recorded by conventional three-component geophones,plus the cable-wave and“spring-wave”interferences.These two types of interference are caused by the seismic wave energy reaching the cable through different paths,which causes the cable to vibrate.The cable-wave interference can be suppressed via random median filtering,whereas the“spring-wave”interference can be suppressed by the inversion method.Test results on field data demonstrated a reasonable recognition of the wavefield characteristics of the interference waves,and that the adopted noise suppression strategy was effective.After suppression of the interference waves,the imaging profile obtained via the DAS system was consistent with that obtained via surface seismic methods,suggesting a good application potential of the DAS system in wells.
作者
吕公河
牟风明
刘小会
刘雪洁
尚盈
LV Gonghe;MU Fengming;LIU Xiaohui;LIU Xuejie;SHANG Ying(Sinopec Geophysical Corporation,Beijing 100020,China;Shengli Branch of Sinopec Geophysical Corporation,Dongying 257086,China;Laser Institute,Qilu University of Technology (Shandong Academy of Sciences),Jinan 250103,China)
出处
《石油物探》
CSCD
北大核心
2022年第1期85-92,111,共9页
Geophysical Prospecting For Petroleum
基金
国家自然科学基金青年基金项目(62005137)
山东省泰山学者工程项目(tsqn20161061)
山东省高等学校青创科技支持计划(2019KJJ004)
中国石油化工集团公司科研项目“井中地震采集系统自主研发”(JP21002)共同资助。
关键词
分布式光纤
DAS
干扰波
压制
缆波干扰
“弹簧波”干扰
distributed optical fiber
DAS
interference wave
suppress
cable wave interference
“spring wave”interference
