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实现过金属套管测量地层电阻率的难点在于突破套管的屏蔽。为了验证低频电磁场穿透金属套管的可能性,进行了金属套管内电磁场响应的理论计算和实验室测量。由于套管内电磁信号非常微弱,设计了专用的大功率电磁场发射装置,研制了弱信号探测的高灵敏探头和高精度测量仪器,实现了金属套管内电磁场信号的激励和测量。测量结果表明,在金属套管内实现低频电磁场激励和弱信号测量是可行的,根据套管内的信号可以获得关于地层的电阻率信息。
The difficulty of measuring the formation resistivity of the metal casing lies in breaking the shield of the casing. In order to verify the possibility of low frequency electromagnetic field penetrating the metal sleeve, theoretical calculations and laboratory measurements of the electromagnetic field response in the metal sleeve were performed. Due to the very weak electromagnetic signal in the casing, a special high-power electromagnetic field emission device is designed and a highly sensitive probe and a high-precision measuring instrument for weak signal detection are developed. The excitation and measurement of the electromagnetic field signal in the metal sleeve are realized. The measurement results show that it is feasible to realize the low-frequency electromagnetic field excitation and weak signal measurement in the metal casing, and the resistivity information about the formation can be obtained based on the signals in the casing.