The contact between drillstring and bore hole wall in the process of horizontal drilling is of large area and geometrically nonlinear. 长中半径水平井钻柱与井壁的接触问题是大面积接触的几何非线性问题。
A transmitter toroid induces a low-frequency current in the drillstring, which flows out of the bit and returns farther up the string. 发射线圈在钻柱内感应出低频电流，从钻头流出，在钻柱上部返回。
