Patent ID: 8826979

Claim:
An apparatus for placing a cement plug in a well, comprising: a pipe for delivering a cement slurry to a predetermined location in the well to be plugged; at least one sensor located at a lower end of the pipe and operable to measure parameters in the well at the predetermined location; wherein the sensor comprises a sensor package that is detachable from the pipe so as to remain at the predetermined location in the well and houses a sensor cable rolled as a bobbin which can be withdrawn to connect the sensor to the operating system at the surface, the sensor being configured to measure at least one parameter relevant to cement plug placement and is connected to the operating system by means of a cable; a release mechanism by which the sensor package is held in the pipe, the mechanism being operable by means of a body that can be pumped through the pipe to detach the sensor package on contact with the mechanism, wherein the body comprises a dart or a ball; and an operating system located at the surface for receiving output signals from the sensor.