随钻超深电磁波仪器探测深度及响应特征模拟

Simulation to Determine Depth of Detection and Response Characteristics while Drilling of an Ultra-Deep Electromagnetic Wave Instrument

  • 摘要: 研究不同天线组合的边界探测深度是研发随钻超深电磁波仪器的基础工作。采用数值模拟方法,研究了轴向天线、水平天线和倾斜天线3种接收天线的探测深度和响应特征,结果发现:随钻超深电磁波仪器的探测深度与线圈距、工作频率及地层电阻率对比度相关;不同电磁场分量对地层界面响应特征不同,超深探测轴向接收天线测电阻率比常规电磁波更容易受邻层影响;采用水平接收天线时,天线距越小,工作频率越大,定向电动势信号幅度越大;采用倾斜接收天线时,天线距越大,工作频率越大,相对定向信号幅度越大。对于随钻超深电磁波仪器,采用水平接收天线时天线距要小,采用倾斜接收天线时天线距要大;多个频率和天线距的组合可以增大随钻超深电磁波仪器的探测深度和对地层电阻率的适应性;通过降低工作频率、增大天线距,可使随钻超深电磁波仪器的探测深度达到20.00~30.00 m。研究认为,该探测深度能弥合地震和测井之间的差距,使随钻油藏描述成为可能。

     

    Abstract: Studying the boundary detection depth while drilling for different antenna combinations is the primary objective of developing ultra-deep electromagnetic wave instruments. The numerical simulation method has been used to study the boundary detection depth and response characteristics of three kinds of receiving antennas: axial antenna, horizontal antenna and tilted antenna. The simulation analysis suggested that the detection depth while drilling for the ultra-deep electromagnetic wave instrument was related to the antenna spacing, operating frequency and the formation resistivity contras. Further, it became clear that different electromagnetic field components had different response characteristics to the formation interface, and the axial resistivity measurement of ultra-deep detector was more likely to be affected by adjacent layers than the conventional electromagnetic waves. When the horizontal receiving antenna was used, the smaller the antenna spacing and the higher the operating frequency, the larger the potential signal amplitude of directional electromotive force. Then, when the tilted receiving antenna was used, the larger the antenna spacing and the higher the operating frequency, the larger the potential relative directional signal amplitude. While using the ultra-deep electromagnetic wave instrument while drilling, the antenna spacing should be small when the horizontal receiving antenna is used, and the distance should be large when the tilted receiving antenna is used. Further, the combination of multiple frequencies and antenna spacing can increase the detection depth while drilling and therefore, the adaptability to the formation resistivity of ultra-deep electromagnetic wave instrument. By reducing the operating frequency and increasing the antenna spacing, the detection depth of ultra-deep electromagnetic wave instrument while drilling can reach 20−30 m. The study showed that the detection depth could bridge the gap between seismic and well logging, and make it possible to describe the oil reservoir while drilling.

     

/

返回文章
返回