垂直线电流源的三维电阻率成像

在油井注水和深井注浆的电法监测中,地表布设平面的电位测量网,而将钻井的钢套管作为线电流源来供电,据此可确定流体的运动方向和分布特征.数据处理中需解决垂直线电流源的三维电阻率反演.本文叙述了相应的反演理论和偏导数计算方法.在某油田的试验中,以生产井为电极圈的中心,每圈均匀布设18个电极,共6圈,在地表得到了108个电位数据,获得500～2 000m之间5个不同深度层的真电阻率分布图像,并对深度层为1 500～1 600m的图像进行了初步解释.结果表明,该方法可以对井下某深度层中的流体运动和分布可进行有效的监测.

3-D Resistivity Inversion of a Vertical Line Source of Current

In monitoring water- or mud-injection of oil well by electrical method, the potential electrodes are placed on the surface and the corresponding current electrode is the steel case of oil well which is a vertical line source of current. The purpose of exploration is to reveal the flow direction and distribution of fluid through these observed data. 3-D resistivity inversion of a vertical line source of current and a method of constructing Jaccobian matrix are introduced in this paper. A preliminary result from a test oilfield is presented. An oil production well is taken as a vertical line source of current, around which 108 electrodes are placed evenly at 6 circles with 50 m space in radius. The medium true resistivity values of 5 horizontal layers ranging from 500 m to 2 000 m deep are obtained. The result shows that this method is effective to monitor the direction and distribution of fluid in a certain layer.