Measurement of Oil and Water Flow Rates in a Horizontal Well With Chemical Markers and a Pulsed-Neutron Tool
- Bradley A. Roscoe (Schlumberger-Doll Research) | Chris Lenn (Schlumberger Oilfield Assistance Ltd.) | T.G.J. Jones (Schlumberger Cambridge Research) | Colin Whittaker (Schlumberger Cambridge Research)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- May 1997
- Document Type
- Journal Paper
- 94 - 103
- 1997. Society of Petroleum Engineers
- 4.1.4 Gas Processing, 5.3.2 Multiphase Flow, 7.2.2 Risk Management Systems, 3.3.1 Production Logging, 4.1.2 Separation and Treating, 5.2.2 Fluid Modeling, Equations of State, 5.2.1 Phase Behavior and PVT Measurements, 5.2 Reservoir Fluid Dynamics, 4.1.5 Processing Equipment, 1.14 Casing and Cementing, 5.6.5 Tracers
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A new approach to obtaining oil and water flow rates in producing horizontal wells has been developed with a pulsed-neutron tool (PNT). This approach uses separate measurements of oil and water velocities in combination with separate holdup measurements to obtain the flow rates.
The velocity measurement uses water-soluble and oil-soluble chemical markers, both of which are insoluble in the other fluid phase for the measurement. The markers are injected into the borehole by a logging tool at one location and detected by a PNT at a second location. The transit time between injection and detection of the marker gives a measurement of the fluid velocity. Because the markers are soluble in only one phase, the velocity of each phase can be measured separately. This measurement has been made under both laboratory and field conditions to measure velocities from 10 to 500 ft/min at horizontal and several degrees deviation from horizontal. The results of these tests show good linearity and repeatability of the measurement.
The holdup measurement is performed with the inelastic data from a PNT. With these data, it is possible to obtain quantitatively the holdup of all three phases by combining information from the inelastic near/far (N/F) ratio with the near and far carbon/oxygen (C/O) ratios. This approach to the holdup measurement has been demonstrated by use of a combination of laboratory data, Monte Carlo modeling, and field data. The results of this study have demonstrated that the root-mean-square (RMS) accuracy of this measurement is about 6% on each of the three phases.
As horizontal wells have become more prevalent, the ability to reliably evaluate the production performance of these wells has become increasingly important. Existing production-logging techniques, such as spinners, that have been successfully used in vertical wells cannot always be applied to horizontal wells with full confidence owing to the segregated flow in the borehole. For this reason, new techniques must be developed to evaluate oil and water flow rates in horizontal wells.
To determine the flow rates of the oil and water phases in a horizontal well, one must measure either (1) the individual oil and water flow rates directly or (2) the individual oil and water velocities in addition to their holdups. (Note that, for most production-logging applications in horizontal wells, measuring only the holdup or only the velocity of the production fluids is usually insufficient to determine the source of production problems.) This paper will address the second approach, the measurement of individual oil and water velocities and their holdups.
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