井中磁源瞬变电磁响应特征研究

井中瞬变电磁波勘探是一个全空间地球物理场问题.采用Gaver-Stehfest逆拉氏变换方法,正演计算了瞬变信号激励下接收线圈上的电磁场响应.分析了包含井眼泥浆、套管、水泥环和地层的轴对称多层介质模型的电磁场响应特征,考察了各层介质参数对井中瞬变电磁响应的影响.不同电导率井眼泥浆的电磁场响应衰减曲线表明,井眼泥浆电导率...

Research on transient electromagnetic response of magnetic source in borehole

The transient electromagnetic exploration in borehole is a full space geophysical problem. The Gaver-Stehfeest inverse Laplace transform is used to theoretically calculate the transient electromagnetic response in the receiver loop. And the effects of the parameters of the borehole mud, metal casing, the cement sheath and the formation on electromagnetic logging responses are analyzed. The response curves of different electrical conductivity of the borehole mud indicate that the borehole mud has little effect on the electromagnetic responses. The numerical results of different geometry of the casing pipe show that the inner radius and the thickness of casing have an obvious effect on the logging responses, moreover, the abnormality of transient response appears where the casing thickness suddenly increases or decreases. The simulation results of different magnetic permeability of the casing pipe show that it has an important effect on transient response in borehole and the higher the magnetic permeability, the more difficult the electromagnetic signals through the casing. The results of different parameters of the cement sheath indicate that the high conductive cement sheath can generate large measurement error for low conductive formation. It is also found that the effect of the thickness of the cement sheath can be ignored for high conductive formation.