The central axis line of a well or a pipeline with a position vector \bf r at each point of trajectory given as:
(1) | {\bf r} = {\bf r}(l)= \{ x(l), \, y(l), \, z(l) \} |
where
{\bf r}(l) | position vector of trajectory points with z(l) being a vertical direction |
l | path length from pipeline intake point {\bf r}_0 |
{\bf r}_0 | pipeline intake point coordinates \{ x_0 = 0, \, y_0 = 0, \, z_0 = 0 \} |