Fluid flow measurement using optical fibres

Apparatus for monitoring fluid flow, comprising:

• an optical fibre having a heatable coating for disposing in thermal contact with flowing fluid;
• a power source operable to heat the heatable coating so that heat is transferred from the coating to the fluid;
• an optical source operable to generate light and launch the light into the optical fibre;
• a photodetector operable to detect light from the optical fibre;
• and
• a processor operable to process the detected light to obtain information indicative of the temperature of the heatable coating, where the temperature of the heatable coating depends on the flow.

A method of monitoring fluid flow in an oil well, comprising:

• providing an optical fibre having a heatable coating;
• deploying the optical fibre downhole in an oil well such that the heatable coating is in thermal contact with flowing fluid;
• heating the heatable coating so that heat is transferred from the coating to the fluid;
• launching light into the optical fibre;
• detecting light from the optical fibre;
• processing the detected light to obtain information indicative of the temperature of the heatable coating, where the temperature of the heatable coating depends on the flow;
• and
• using the information indicative of the temperature of the heatable coating to derive information about the flow.

A method of detecting scale within a well bore, comprising:

• providing an optical fibre having a heatable coating;
• deploying the optical fibre downhole within a well bore so that the heatable coating is in thermal contact with fluid flowing within the well bore;
• heating the heatable coating so that heat is transferred from the coating to the fluid;
• launching light into the optical fibre;
• detecting light from the optical fibre;
• processing the detected light to obtain information indicative of any variation in temperature of the heatable coating with depth within the well bore, where the temperature of the heatable coating depends on the flow of the fluid;
• monitoring the temperature information for any changes in temperature of the heatable coating with depth within the well bore;
• and
• identifying any change in temperature with a change in fluid flow within the well bore caused by scale deposition at that depth.