Dual-Spaced Neutron II Tool (DSN II™)
| The DSN
II tool is a thermal neutron tool designed to measure
formation porosity from neutron-nuclei interactions.
Neutron porosity logs provide total fluid information
for use with resistivity logs and/or pulsed neutron logs
in determining formation water saturation. They can be
combined with density logs to provide an indication of
formation gas saturation and also with density and/or
sonic logs to provide indications of formation
lithology. In open holes, the DSN II tool is usually
combined with the Spectral Density Logging Tool (SDLT™)
and the Natural Gamma Ray Tool (NGRT™). In cased holes,
the DSN II tool is usually combined with the NGRT tool
and DITS™ casing collar locator. |
|
| The DSN
II tool consists of an instrument section housing the
electronics, two He3 detectors, and a source sub housing
an americium-beryllium source which generates fast
neutrons that penetrate the formation at an initial
energy of 4.6 MeV. Thermal neutron tools are not as
limited by the spacing and depth of investigation
problems associated with epithermal neutron tools. Since
thermal neutrons are detected, count rates are much
higher than for epithermal neutrons. However, thermal
neutron detectors are more sensitive to lithology and
are affected by borehole and formation salinity. The
dual detector method is used to compensate for these
environmental effects. DSN II tool applications
include: |
- Gas Detection
- Porosity
- Lithology
|
| » DSN II™ Tool Benefits |
| The DSN
II service delivers porosity measurements with greater
accuracy and repeatability than any other neutron
porosity service. Designed for use in fluidfilled open
or cased holes, this service provides: |
- Superior accuracy. More consistent measurements
over the entire porosity range, even in cased
holes
- Repeatable results. Optimized detector spacing, advanced calibration methods and greater counting rates contribute to the service’s outstanding precision
- Faster Log runs. The optimized design help save
rig time by allowing logs to be run at faster cable
speeds
- Improved thin bed evaluation. Clearer delineation of thin-bed formations with Enhanced Vertical Resolution (EVR) available in real-time or in post-processing
- Increased reservoir understanding. A combination of logging tools can be run to identify lithology, reveal gas zones and calculate shale volumes
|
|
|
 |
| In this
DSN II log example, the subject well was logged twice.
The resulting near/far ratio curves and the calculated
porosity curves are overlaid to illustrate the high
repeatability of DSN II porosity measurements. |
| |
| » DSN II Tool Features |
| The DSN
II tool detector array contains two helium proportional
counters. The DSN II tool can be combined with most DITS
tools. Typical combinations could be: NGRT or CSNG™, DSN
II, SDLT, or the preceding combination run in a tool
stack with DLLT/MSFL™, HRI™/DFL, and/or FWST™. |
|
| » Associated Answer Products |
| The
following answer products are associated with the DSN II
tool: |
- The wellsite answer product is the neutron
porosity NPHI
|
- Neutron porosity data is also used with other open
hole sensors as input to Halliburton’s mineralogy,
open hole, and cased hole saturation analysis to
provide a complete formation evaluation product. These
include:
- ULTRA™ (Multi-Mineral Evaluation Program)
- CORAL™ (Complex Lithology Analysis)
- LARA™ (Laminated Reservoir Analysis)
- SASHA™ (Shaly Sand
Analysis)
|
|
|
| Length |
Diameter |
Maximum
Pressure |
Maximum
Temperature |
Weight |
| (ft) |
(m) |
(in) |
(mm) |
(psi) |
(Mpa) |
(°F) |
(°C) |
(lb) |
(kg) |
| 10.25 |
3.1 |
3.63 |
92.2 |
20,000 |
137.9 |
350 |
176.7 |
196 |
88.9 |
|
|
