Method for signalling a downhole device in a well

摘要

A method and apparatus for controlling the operation of a well involves locating a pressure monitoring device downhole and arranging it to be operative: to monitor a characteristic pressure profile of a well during a certain time span controlled by a downhole clock associated with the device; to monitor the temperature downhole in the region of the clock; to calibrate a time reading of the downhole clock with reference to the monitored temperature to correct for drift between the clock time and real time resulting from the downhole elevated temperature; and to respond and generate a triggering output when a significant deviation to the pressure profile is introduced into the well as a control signal to the monitoring device, by comparing two separate pressure profiles within the time span, the device only generating the triggering output when the same pressure profile is monitored twice within the time span.

主权项

1. A method for controlling the operation of a well, the method comprising the steps of:
locating a pressure monitoring device downhole; arranging the pressure monitoring device so that it is operative:
to monitor a characteristic pressure profile of the well during a certain time span; andto respond and generate a triggering output when a significant deviation to the pressure profile is introduced into the well as a control signal to the monitoring device, by comparing two separate pressure profiles within the time span, the device only generating the triggering output when the same pressure profile is monitored twice within the time span; arranging an actuator so that it is initiated into operation to control any required operation of the well when the monitoring device responds to the control signal and generates the triggering output; in which the method comprises the further steps of: arranging the pressure monitoring device to monitor the characteristic pressure profile during the specified time span controlled by a downhole clock associated with the device; monitoring the temperature downhole in the region of the clock; and calibrating a time reading of the downhole clock with reference to the monitored temperature, to correct for drift between the clock time and real time resulting from the elevated temperature which the clock is exposed to downhole.