基于声波垂直入射于井壁的随钻远探测方法及初步数值模拟  

Preliminary Numerical Simulation of Acoustic Reflection Imaging Logging While Drilling Based on the Vertical Incidence of Acoustic Waves on the Borehole Wall

作　　者：刘西恩[1] 赵腾 车小花[2,3] LIU Xien;ZHAO Teng;CHE Xiaohua(China Oilfield Services Limited,Beijing,101149,China;State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing 102249,China;Key Laboratory of Earth Prospecting and Information Technology,Beijing 102249,China)

机构地区：[1]中海油田服务股份有限公司,北京101149 [2]中国石油大学油气资源与探测国家重点实验室,北京102249 [3]北京市地球探测与信息技术重点实验室,北京102249

出　　处：《测井技术》2023年第5期542-550,577,共10页Well Logging Technology

基　　金：国家自然科学基金“三维散射声波远探测扫描成像测井方法研究”(12274465)。

摘　　要：目前随钻声波远探测测井技术受到大振幅井孔模式波的干扰、声源斜入射于井壁的影响,导致回波传播路径长,来自井旁异常体的回波信号的信噪比往往很低。针对上述不足,提出了一种由相控线阵声波辐射器及其邻近的柱面阵声波接收器组成的随钻声波远探测测井方案。井下相控线阵声波辐射器辐射的声波近乎垂直入射于井壁,能够在地层中产生尽可能多的纵波。声波接收器离发射器很近,可以接收沿较小的声学路径传播的井旁异常体回波信号,从而提高回波信号的信噪比。此外,应用柱面阵声波接收器可以获得准确的方位测量结果。采用三维有限差分方法对新方法进行初步数值模拟,结果表明井内声源在井旁地层中产生纵波和横波,其中纵波主要沿垂直于井轴的方向传播,横波主要沿井眼上下侧向传播,这说明纵波更有利于探测距离井轴较远的井旁异常体;来自井旁地层界面的PP回波的到时与方位呈现出近似的正弦关系,不同方位接收的波形极性相同、幅度不同,具有相似性;最靠近地层界面所在方位的接收单元接收的PP回波到时最早,振幅最强;随着地层界面越来越远,PP回波到时越来越晚,振幅越来越小。将新方法与现有方法进行对比,结果表明该方法能够同时压制井孔模式波和增强井外地层中的纵波能量,从而有效增强随钻声波远探测测井回波信号的信噪比。该研究为随钻远探测装置设计和后续的实验研究提供了理论依据。The current acoustic reflection imaging logging while drilling(LWD)technology is affected by the interference of large amplitude borehole mode waves and the oblique incidence of acoustic waves on the borehole wall,resulting in a long propagation path of echoes.The signal-to-noise ratio(SNR)of the echo signal from the well-side anomalies tends to be low.In response to these shortcomings,an acoustic reflection imaging LWD scheme consisting of the linear phased array acoustic transmitter and its adjacent cylindrical array acoustic receiver is proposed.The downhole linear phased array acoustic transmitter radiates acoustic waves that are incident nearly vertically on the borehole wall,generating as many P-waves as possible in the formation.The acoustic receiver,which is very close to the transmitter,can receive the echo signal from the well-side anomalies propagating along a smaller acoustic path,thereby improving the SNR of the echo signal.In addition,the application of the cylindrical array acoustic receiver can obtain accurate azimuth measurement results.A preliminary numerical simulation study of the proposed method was carried out using a 3D finite difference method.The simulation results show that the acoustic source in the well generates P-waves and S-waves in the formation near the well,where P-waves mainly propagate in the direction perpendicular to the well axis,and S-waves mainly propagate along the upper and lower lateral directions of the well.This indicates that P-waves is more beneficial to detect anomalies that are far away from the well axis.The arrival time of the PP-waves from the formation interface shows an approximate sinusoidal relationship with the azimuth angle of the receiver,and the PP-waves recorded by receivers with different azimuth angles have the same polarity and are similar.The PP-waves received by the receiving unit nearest the formation interface arrives earliest and has the largest amplitude.As the distance between the formation interfaces and the well increases,the arrival time o

关 键 词：随钻声波测井 声波远探测 相控阵 数值模拟 

分 类 号：P631.84[天文地球—地质矿产勘探]