The reduction in reservoir pressure may tend to draw up underlying water towards the well in a cone like shape if an oil well is produced at excessive rates. Like-wise gas can be drawn downwards from an overlying gas cap.
see water coning.
The upward angular displacement of the rotor blades of a gyroplane or helicopter under the influence of lift. The Coning Angle is the angle between the rotor blades and the plane normal to the axis of the hub.
Found on http://www.aeroplanemonthly.com/glossary/
No exact match found