Pressure equalising devices
An electronic actuation system for a pressure equalizing device in a downhole apparatus such as a wellbore plug is described. The system includes a pressure sensor for measuring pressure in the wellbore, and means for setting a reference pressure value using a measurement from the pressure sensor. In a method of use, an applied pressure value is determined using a measurement from the pressure sensor and the reference pressure value, and the device is actuated, or opened, when the applied pressure meets a pre-determined condition, such as falling within a pressure window for certain time period. The invention allows natural changes in wellbore pressure to be accounted for when detecting a pressure actuation event.
1. An electronic actuation system for a pressure equalizing device in a wellbore plug, the system including a pressure sensor for measuring pressure in the wellbore, a reference pressure value setting module which uses a measurement from the pressure sensor to set a reference pressure value, a module programmed to determine an applied pressure value using a measurement from the pressure sensor and the reference pressure value, and a module programmed to determine a rate of change in pressure measured by the pressure sensor.
2. The electronic actuation system as claimed in claim 1 , further comprising a processor module for setting the reference pressure value.
3. The electronic actuation systems as claimed in claim 1 , wherein the pressure sensor is arranged to measure wellbore pressure above the wellbore plug.
4. The electronic actuation system as claimed in claim 3 , further comprising a second pressure sensor for measuring pressure below the plug.
5. The electronic actuating system as claimed in claim 1 , further comprising a memory unit for storing measured pressure values.
6. The electronic actuation system as claimed in claim 5 wherein the processor module is programmed to compare a pressure gradient with a reference pressure value.
7. A wellbore plug incorporating the downhole apparatus as claimed in claim 1 .
8. Downhole apparatus comprising: a body for locating on a work string; one or more ports provided in the body for passage of fluid between regions of the wellbore above and below the apparatus; an actuating member moveable relative to the body from a first position in which the ports are closed to prevent fluid flow therethrough, and a second position in which the ports are open to allow fluid flow therethrough, and an electronic actuating system for controlling movement of the actuating member from the first to second position; wherein the electronic actuating system includes a pressure sensor for measuring pressure in the wellbore, a reference pressure value setting module programmed to set a reference pressure value using a measurement from the'pressure sensor, a module programmed to determine an applied pressure value using a measurement from the pressure sensor and the reference pressure value; and a module programmed to determine a rate of change in pressure measured by the pressure sensor.
9. The downhole apparatus as claimed in claim 8 , wherein the electronic actuation system is as claimed in claim 1 .