Research On Interpretation Method Of Downhole Transient Electromagnetic Data

The transient electromagnetic method is sensitive to the reaction of low-resistance anomalous bodies and is currently an effective method for detecting the goaf water area.For the double-layer goaf area,it is affected by the "low resistance shielding" of the upper goaf water area.It is not easy to delineate the accurate range of the mined-out water accumulation area underneath.Mine transient electromagnetic method is generally used for detection in construction roadways.The working environment of construction roadways is complicated and the interference is more serious.It is a comprehensive response of the entire underground space and often causes ambiguity.To solve the above problems,the method of combined interpretation of ground transient electromagnetic and mine transient electromagnetic data is adopted: that is,the ground transient electromagnetic method is used to detect downwards,and the main target layer is the upper mined out water area,and at the same time in the coal mining face.In the roadway on the side,the mine transient electromagnetic method is used to detect upwards.The main target layer is the mined-out water area in the lower part.The data collection and comprehensive interpretation can be carried out to avoid the influence of low-resistance layers.First,the feasibility of joint interpretation is analyzed,through the transient electromagnetic forward modeling under the half-full space conditions of different geoelectric models such as different scales,different water fills,different buried depths,and double-layer mined-out areas developed in coal-measure strata.Numerical simulation calculations analyze the transient electromagnetic response characteristics of the half-space and full-space goaf areas with different characteristics.From the numerical simulation results,it can be seen that the transient electromagnetic response is very weak for the unfilled goaf area;for the single-layer waterfilled goaf area with different characteristics,the half-space and full-space transient electromagnetic response characteristics are basically the same: detection distance The smaller,the larger the water-filled volume,the stronger the transient electromagnetic response,and as the distance increases,the later the anomaly appears;for the double-layer water-filled goaf,under full and half-space conditions The transient electromagnetic response is stronger than that of the single-layer water-filled goaf,and its resolution is lower.It only has a good resolution for the "relative" first-layer water-filled goaf.Combining the two can realize the double-layer goaf.Zone detection.Subsequently,on the basis of numerical simulation,combined with the actual situation of the study area,a joint interpretation of the mine transient electromagnetic and ground transient electromagnetic data in the relevant study area is carried out.Compared with the data interpretation of the single transient electromagnetic method,the joint interpretation is for the mined-out product.The delineation range of the water area is smaller,and the result is more accurate.This paper uses the combined interpretation method of ground and mine transient electromagnetic method,which shows that the comprehensive interpretation of the two transient electromagnetic methods has a good effect on the detection of complex goaf areas in coal mines.