Geometrics MicroEel Manuale utente
MicroEel
Solid Analog Streamer
P/N 60101-13 Rev. C
May 6, 2012
Operation Manual
GEOMETRICS, INC.
2190 Fortune Drive
San Jose, CA 95131 USA
Tel: (408) 954-0522
Fax: (408) 954-0902
support@geometrics.com
www.geometrics.com
COPYRIGHT © 2011, 2012
Table of Contents
1 – INTRODUCTION....................................................................................................... 4
2 – SYSTEM COMPONENTS........................................................................................ 5
2.1 CABLE.................................................................................................................. 5
2.1.1 Hydrophones............................................................................................... 7
2.1.2 Hydrophone Preamplifiers.......................................................................... 7
2.1.3 Deck and Tow Cable Connector Terminations........................................... 7
2.1.4 Cable Crate................................................................................................. 9
2.2 POWER SUPPLY AND REQUIREMENTS ................................................................ 10
2.2.1 DHA-7/MicroEel Battery Pack................................................................. 10
2.2.2 Power Consumption.................................................................................. 12
2.2.3 AC Battery Charger.................................................................................. 12
3 – SYSTEM SET-UP.................................................................................................... 13
3.1 INTERCONNECTIONS........................................................................................... 13
3.2 DEPLOYMENT .................................................................................................... 13
3.3 BATTERY CHARGING ......................................................................................... 14
4 – APPENDIX ............................................................................................................... 16
4.1 CONNECTOR WIRING ......................................................................................... 16
4.2 CALIBRATION..................................................................................................... 16
4.3 SPECIFICATIONS ................................................................................................. 17
4.4 WARRANTY AND SERVICE ................................................................................. 18
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List of Figures
Figure 1. MicroEel active section with solid flotation (green) and tow cable (black)....... 4
Figure 2. MicroEel solid analog streamer block diagram.................................................. 6
Figure 3. Topside deck cable connector terminations (NK-27 termination not shown).... 8
Figure 4. Deck cable 55-socket connector termination. .................................................... 8
Figure 5. Tow cable 55-pin connector termination shown with Kellems grip. ................. 9
Figure 6. Crate for transport, storage, and deployment. .................................................. 10
Figure 7. DHA-7/MicroEel Battery Pack. ....................................................................... 11
Figure 8. Detail of DHA-7/MicroEel Battery Pack. ........................................................ 11
Figure 9. Sheet lead, tin snips, and Bulldog tape............................................................. 14
Figure 10. DHA-7/MicroEel-D Battery Pack wiring....................................................... 16
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1 – Introduction
The MicroEel Solid Analog Streamer is designed for high-resolution marine seismic
imaging. It is ideal for shallow oil and gas investigations, stratigraphic and structural
mapping, and teaching and research.
The MicroEel features solid-type construction specifically designed to withstand the
harsh conditions of commercial marine surveys. The active section is built using
Geometrics continuous-flotation molding method (Figure 1).
Figure 1. MicroEel active section with solid flotation (green) and tow cable (black).
In addition, the MicroEel uses unique proprietary polymer hydrophones, which unlike
ceramic hydrophones are non-shattering. Polymer hydrophones provide superior
durability and performance under the rigors of marine applications with a stable signal
response up to 10 kHz.
Depending on your location, the MicroEel may require a US Department of Commerce
license for export.
This manual provides operating instructions, including description of the MicroEel
system components, setup, calibration, and warranty.
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2 – System Components
The standard MicroEel Solid Analog Streamer system includes the following items:
Active section cable with tow cable, tail and eye bolt, and deck cable, coiled in a
plastic crate
DHA-7/MicroEel Battery Pack
Universal AC battery charger for the DHA-7/MicroEel Battery Pack
CD with support documents (*.pdf) including the operations manual, connector
wiring tables, and hydrophone calibration plots
2.1 Cable
The active section consists of a series of hydrophone groups, with the number of groups
equal to the number of channels, either 12 or 24 as a standard; other channel counts are
available through custom order. The available group intervals are a minimum of 1 m and
a maximum of 6.25 m in length. For group intervals between 3.125 and 6.25 m, there are
three depth-limited hydrophones spaced 0.11 m apart (0.22 m aperture) with the signal
summed electrically and connected to a preamplifier. For hydrophone groups less than
3.125 m, there is one hydrophone per group connected to a preamplifier. Other
hydrophone counts per group are available through custom order. All of the components
are in-line molded to a multi-conductor cable with a polyurethane jacket and Kevlar
center stress core; this is further encased in Geometrics’ proprietary solid flotation
material.
The tow, active section, and tail cables are all one integrated piece, with no
interconnections in between. The tow cable connects to a topside deck cable. The deck
and tow cables are terminated with mating waterproof connectors. The opposite end of
the deck cable is finished with a Y-type termination to connect to the DHA-7/MicroEel
Battery Pack and seismograph. The total maximum length of the streamer from head of
the deck cable to tail of the active section is 400 m.
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Figure 2. MicroEel solid analog streamer block diagram.
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2.1.1 Hydrophones
The streamer uses Geometrics’ unique proprietary polymer hydrophones. The
hydrophone incorporates design features offering superior performance compared to
previous polymer hydrophone designs as well as the traditional PZT ceramic-type
hydrophones. Specifically, it is non-shattering and incorporates an isolating platform,
making it immune to cable-borne energy. In addition, other design aspects allow its
response to acoustic pressure alone to dominate the output.
The hydrophones are depth-limited and become inoperable at depths greater than 30 ±5
m. The inoperable state is temporary and functionality fully recovers when the depth is
reduced. This limitation allows the MicroEel to be exported under less strict US
Department of Commerce laws.
2.1.2 Hydrophone Preamplifiers
The true differential preamplifier used with the hydrophone is of a single-pole low-cut
and a single pole high-cut design. The low-cut frequency is determined by the ½πRC
time constant which is related to the element capacitance and the input resistance of the
preamplifier front-end. The preamplifier features exceptionally low noise. Nominal
element capacitance is 7.2 nF at 22 degrees C. The design also provides full voltage
regulation at each preamplifier. The voltage regulator isolates each channel from the
other which is desired when all preamplifiers share a common power bus.
2.1.3 Deck and Tow Cable Connector Terminations
The standard topside deck cable termination is a Y-type with one 61-socket connector
(PT06J-24-61S) for analog output, and one 4-pin connector [PT06A-8-4P(SR)] for power
connection to the DHA-7/MicroEel Battery Pack (Figure 3). As an option, the analog
output termination may be ordered with a 27-socket connector(s) (NK-27-21C) instead of
the 61-socket connector. Adaptor cables are also available to connect to seismographs
with other analog input connector types.
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4-pin
connecto
r
61-socket
connecto
r
Figure 3. Topside deck cable connector terminations (NK-27 termination not shown).
The standard deck cable termination for analog input from the tow cable is one 55-socket
waterproof connector (Glenair 220-06E16-55SN) (Figure 4).
Figure 4. Deck cable 55-socket connector termination.
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The standard tow cable termination for analog output to the deck cable is one 55-pin
waterproof connector (Glenair 220-01E16-55PN) (Figure 5).
Figure 5. Tow cable 55-pin connector termination shown with Kellems grip.
The connector pair between the deck and tow cables feature red marks on their collars to
indicate when pin and socket are aligned.
2.1.4 Cable Crate
The streamer is shipped coiled in a crate for storage, transport, and deployment (Figure
6). The crate is fully composed of inorganic plastic to comply with international shipping
regulations.
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Figure 6. Crate for transport, storage, and deployment.
2.2 Power Supply and Requirements
The streamer is powered by the DHA-7/MicroEel Battery Pack. The battery pack is
rechargeable using the included AC battery charger.
2.2.1 DHA-7/MicroEel Battery Pack
The DHA-7/MicroEel Battery Pack (Figure 7) contains two 12V DC deep discharge (5
Amp-hour) sealed lead-acid batteries used in a ±12V DC differential power
configuration. The deck cable power lead is connected to the battery pack via the 4-
socket connector located on the right-hand side of the battery pack. This connector is also
used to connect the AC battery charger. Next to the connector is a grounding post (¼”-20
bolt and nut).
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