随钻前视声波测井钻头前方声场特征研究

The Characteristics of the Acoustic Field Ahead of the Bit in“Look-Ahead”Acoustic Logging While Drilling

现有声波测井仪器无法满足前视探测需求,为此开展了基于相控阵技术的随钻前视声波测井技术研究。采用相控线阵声波辐射器和相控圆弧阵声波接收站,分别实现声波能量的定向辐射和扫描接收;利用有限差分算法,分别模拟了随钻条件下钻头前方存在一个地层界面时的单极和相控阵声波测井响应。模拟结果表明,由于井底散射的影响,随钻前视声波测井的波场比常规反射声波测井的声场更为复杂;与单极声波辐射器相比,相控线阵声波辐射器能够定向增强辐射到钻头前方地层中的声波能量,可以显著增强P-P回波的幅度;与单极声波接收器相比,通过统计相控圆弧阵声波接收站扫描接收到的不同方位P-P回波的幅度,可以近似判断钻前地层界面的方位。研究结果验证了利用相控阵声波测井技术探测钻前地质异常体的可行性,为后续工业样机的开发提供了理论依据。

As the existing acoustic logging tools cannot meet the requirements of"look-ahead"detection,the research on“look-ahead”acoustic logging-while-drilling(LWD)was performed based on the phased array technology.The directional radiation and scanning reception of acoustic energy were realized by the linear phased array(LPA)acoustic wave radiator and arcuate phased array(APA)acoustic receiver stations.The responses of monopole and phased array acoustic logging with a formation interface ahead of the drill bit are numerically simulated by the finite-difference algorithm.The results showed that the acoustic fields of“look-ahead”acoustic LWD are more complex than those of conventional acoustic reflection logging,because of the wave scattering at the well bottom.Compared with the monopole acoustic radiator,the amplitude of P-P echo can be significantly enhanced by directionally enhancing the acoustic energy radiated into the formation ahead of the drill bit with LPA acoustic wave radiator.Compared with the monopole acoustic receiver,the APA acoustic receiver station can approximately determine the azimuth of the formation interface ahead of the drill bit by analyzing the amplitude distribution of P-P echo waves in the scanning reception waveforms.The research results confirmed that detecting geological anomalies ahead of the drill bit with phased array acoustic logging is feasible,and it can provide a theoretical basis for the development of industrial prototypes.