A Prototype of a Fiber-optical Downhole Measurement System of Pressure, Temperature And Flow

A prototype of a downhole measurement system is described in this paper that uses fiber Bragg grating (FBG) sensors without electrical circuits in the downhole part. Such a device could potentially allow small sensors to be deployed in harsh borehole environments. We have tested and demonstrated the measurements of pressure, temperature and fluid flow velocity. Pressure and temperature measurements are discriminated using a dual-sensitivity FBG system. The system showed linear responses within an expected range and noise levels of 0.18 MParms, and 0.14 deg-Crms, . For the flow measurement, the system uses cross-correlation and Karman vortex shedding frequency techniques. It has been demonstrated from the laboratory tests that the system has a linear response up to 1.00 m/s and the minimum detectable velocity of 0.05 m/s.