Tubing Weight Operation for a Downhole Tool

摘要

A downhole tool has housing components that are relatively movable. One of the components is supported downhole while a control line provides fluid pressure to move the other housing component relative to the supported component to put the tool in a first position. Loss of control line pressure allows the weight of tubulars bearing on the upper housing or rods to move it to put the tool in another position. The tubing weight overcomes the hydrostatic pressure in the control line even when there is no applied pressure in the control line to cause relative housing or rods movement to operate a tool. In that sense the tool can be fail safe to shut off flow, for example, on loss of control line pressure while reducing or elimination the need for a large return spring to offset hydrostatic pressure.