The Fluid Identification Tool is used to make logs of the fluid mixture Density and Capacitance. The combination of measurements allows calculation of individual holdups in three-phase oil/water/gas mixtures.
The tool replaces the conventional separate fluid density and capacitance tools with greatly improved accuracy and range due to new sensors and simultaneous sampling on the same volume of fluid. Correlation of the two sensor readings may be made 16 times per second to compensate for separation of the fluid phases in slug or turbulent flow. This is not possible when the sensors are separated by a significant distance along the tool string.
This new sensor uses an internal 1 mCi Ba-133 Radioactive Source (50 times less strong than competing tools) and super-sensitive scintillator crystal with a photomultiplier for maximum log quality. In some operating conditions, it is possible to log with an Exempt-Quantity Source with minimal loss of resolution. This is a great advantage because licensing issues are reduced or eliminated.
High count-rates (typically 30,000 cps) ensure statistical errors are less than 0.01 gm/cc. (with averaging over 1 second intervals) and minimize the influence of NORM (Naturally Occurring Radioactive Material) radiation. The detector is also fully shielded from NORM if it is present on the casing wall. The electronics are temperature compensated to maintain accurate count-rates at all rated temperatures.
The center-sample measurement includes a simultaneous 250 KHz capacitance measurement that senses water content from 0 – 100%. Unlike competing tools, there is no “saturation effect” when water holdup reaches 60 – 70%
The graphs below show typical measured accuracy of the FIT-A for both density and dielectric constant in various materials. Because the curves are very linear, it is possible to use a simple two-point calibration in the field using air and water.