The Study On The Numerical Simulation Of Response Of Wellside Remote Detection Tool

Traditional logging tools are limited by the limited survey depth.In narrow production zones and complex geological environments,it is difficult to meet the needs of the logging site,and the remote detection technology can reach the detection range of several meters to tens of meters to the stratum structure and geological body around the well.Therefore,Based on the COMSOL finite element simulation software,this paper designs a set of coil system parameters for electromagnetic remote detection tool that can detect 30 m away.Then study the boundary detection capability,borehole,intrusion,abnormal body detection and other logging response characteristics of the electromagnetic remote detection tool to provide corresponding theoretical support for electromagnetic remote detection logging.The main research results are divided into the following four parts:The first part builds a three-dimensional stratum model in COMSOL finite element simulation software.By studying the boundary detection capabilities and detection characteristics of zz,xx and xz components,the transmission frequency of the electromagnetic remote detection tool is determined to be 1KHz.Based on whether the layer boundary at a distance of 30 m can be detected,the arrangement of the coil system array and the range of the spacing are given.combined with the engineering implementation requirements of the actual instrument design,the final coil shape,size,number of turns and coil spacing are determined.The second part studies the logging response characteristics of the electromagnetic remote detection tool in the formation model without borehole.The research on the detection accuracy of the instrument under different background conductivities under a uniform formation verifies that the detection accuracy of the tool meets the engineering requirements.Under the two-layer stratum model,the change of the tool response characteristics when the conductivity contrast between the surrounding rock and the target layer changes are researched.When the conductivity of the target layer is 0.01 and 0.1 S/m,the change trend of the signal is opposite.In the performance of the edge detection distance,the edge detection signal is larger because of the higher conductivity of the target layer,so the edge detection distance is farther.The response characteristics of the tool under the three-layer formation when the tool moves from bottom to top through the target layer are studied.The third part studies the logging response characteristics of the electromagnetic remote detection instrument under the formation model with borehole.Calculate and analyze logging response when factors such as well diameter,mud conductivity,contrast,eccentricity and intrusion change.The results show that the borehole has little effect.And at different contrasts,compared with the case without wellbore,because the mud conductivity is greater than the target layer conductivity,the measured signal value has a small change in size,but the magnitude of the change will only affect the edge detection distance when the engineering threshold is 10 n V.The eccentricity research is divided into two types: z-direction offset and y-direction offset.When the tool is offset in the z direction,the measured signal strength changes linearly with the offset.When the tool is shifted along the y direction,the measured signal strength trend is symmetrical along the y axis.The intrusion study divides the six intrusion models into two types according to the high-resistance surrounding rock and the low-resistance surrounding rock,and summarizes the boundary detection characteristics of the electromagnetic remote detection tool under different invasion depths and different invasion models.The fourth part is the response characteristics of anomalous bodies near the well.Calculated and analyzed the geometry of the anomalous bodies near the well and its distance from the tool.The larger the size of the anomalous bodies,the greater the absolute value of the real part of the induced electromotive force.When the side length of the anomalous bodies is greater than 5m,it can be detected by the tool.When the anomalous bodies is a cube and the distance between the tool and the anomalous bodies is 10 m,the axis of the tool is used as the center of rotation,the response law of the xx and xz components with the rotation angle is studied.When judging the azimuth of the anomalous bodies,two components should be used together.By studying the influence of the conductivity contrast between the surrounding rock and the target layer on the detection of abnormal body,we can obtain: The amplitude of the change of the xz component with the contrast signal is greater than the xx component,and the skin effect has more influence on the xx component than the xz component.