The dielectric tool, also known as "water hold-up" or "water cut", measures the capacitance of the fluid that passes between the probe and the body of the tool. This measurement is used to help determine water percentage and to locate first water entry.
The tool is useful when oil is the main phase and the water cut does not exceed 30 percent. The contents in some sour wells will result in inaccurate readings.
- Determine water entry points: with the dielectric tool, there is a big change in the frequency readings between water and air. It is easy to identify the water entry point.
- Identify static fluid interfaces: in an observation well (with no flow), the dielectric tool can be used to record where the different well contents, such as water, oil, solvents, and gas are located. The measurements can be used over a period of time to indicate how the fluids are shifting in level.
- Supplement the interpretation of multi-purpose flow regimes during production logging.
The dielectric probe is generally superior to the nuclear or gradiomanometer density log in distinguishing oil from water. This is a result of the high dielectric contrast that exists between water (approximately 80) and oil (range from 2 to 6). Use of the dielectric tool, however, is restricted to flow conditions where hydrocarbon is the continuous phase, which typically requires a water cut of less than 30 to 40 percent.