1. Field of Invention
The invention is directed to actuator devices for actuating downhole tools and, in particular, actuator devices having a thermally expansive fluid that, when expanded causes actuation of the downhole tool.
2. Description of Art
Some downhole tools need to be retained in an unset position until properly placed in the well. It is only when they are properly located within the well that the downhole tool is set through actuation of the tool. One technique for actuating the downhole tool is to open a window or passageway within the downhole tool exposing the actuating member, e.g., piston, of the downhole tool to the wellbore environment, e.g., the hydrostatic wellbore pressure. The hydrostatic pressure then acts upon the actuating member of the downhole tool and the downhole tool is actuated. In this technique, the creation of the window or passageway does not directly actuate the downhole tool. Instead, the creation of the window or passageway allows a different actuating mechanism, e.g., the hydrostatic or wellbore pressure, to actuate the tool. Additionally, in some instances, hydrostatic pressure is insufficient to actuate the tool.
In other techniques, pressures from fluids pumped down the well are used to actuate the downhole tools. In still another technique, an explosive charge is included as part of the downhole tool. The explosive charge is then detonated by a detonator connected to the surface of the well through an electronic line or connected to battery pack located on the downhole tool. The force from the combustion of the explosive change then acts upon the actuating member and the downhole tool is actuated.