Determination of cementing plug location

摘要

A method which allows for the determination of displacement during a cementing operation involves lowering a dart (72) into engagement with a plug (62) in a wellbore where the location of the plug (62) is measured. The dart (72) may be lowered on an optic fibre (80) and include sensors to determine its position or the position can be calculated from the length of optic fibre (80) lowered into the wellbore. There are also claimed methods of measuring wellbore conditions by use of a optic fibres and sensors.