Method & apparatus for actuating a downhole tool

Abstract

A downhole tool, comprising one or more separate packers and sliding sleeves in the preferred embodiment, is actuable from a nonelectrical signal transmitted from the surface to the tool. The signal is received at the tool by a control system located within the tool. The control system operates in conjunction with a power supply in the tool to accomplish tool actuation. In the preferred embodiment, the valve member is temporarily retained in a sealing position, isolating pressure in one chamber from a different pressure in an adjacent chamber. The valve member or piston is temporarily retained by a high-strength fiber, such as Kevlar.RTM., in the preferred embodiment. The control system actuates the power source to heat a resistance heating wire, which causes failure in the fiber. Other mechanisms to trigger pressure-equalization can be used. The fiber can be cut by a cutter actuated electrically. The piston can be retained by solder which is melted electrically. The piston can be designed to be substantially in pressure balance so that the fiber can effectively hold the piston in place until it is rendered inoperative by heating up a resistance wire from the power supply as triggered by the control circuit. Once the fiber fails, the piston is released and the pressure is equalized. The pressure-equalization can be used to shift a setting sleeve to set a packer or to open or close a sliding sleeve valve. Different valves can be actuated in series, using different control signals, or in parallel, using one control signal. In the alternative, the same valve can be actuated to open and then to close, depending on the procedures desired. The resistance wire is threaded into the fiber cable to ensure effective transmission of the heat for proper release of the piston when desired.