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Model DHA-7

Downhole Hydrophone Array

Individually isolated hydrophone and preamp in-line molded to multi-conductor cable with Kevlar strength member.

  • Image faults and fractures, stratigraphy, voids, mineral deposits, underground structures; determine soil, rock and reservoir properties
  • Ideal for shallow gas and mining investigations, earthquake engineering and foundation studies, teaching and research
  • Suited for high-resolution uphole, VSP, and crosshole surveys
  • State-of-the-art polymer hydrophones provide superior, stable response
  • Unique design isolates vibration and suppresses cable-related noise
  • Small diameter and light weight make for easy deployment
  • Reliably performs under the rigors of borehole applications
  • No export license required
DHA-7

Example crosshole record showing high frequency first breaks. Courtesy of GeoTom LLC

The Model DHA-7 downhole hydrophone array is designed for high-resolution seismic borehole imaging. Unique proprietary polymer hydrophones (no ceramics) are in-line molded to a fully integrated, triple-sealed multi-conductor cable. Non-shattering polymer material provides superior performance and durability under the rigors of borehole applications and a stable signal response up to 10 kHz.

The Model DHA-7 is suited for use in cased and uncased, water-filled, narrow-diameter boreholes. The standard configurations include a group interval of 1 to 5 m and a total cable length of up to 400 m (or 1,300 ft). The cable is terminated topside with a 61-socket connector to mate with the seismograph (optionally terminated with 27-socket connector) and a 4-pin connector to mate with the ±12V DC battery pack. Custom group intervals and multi-borehole configurations are also available to tailor the system to meet your needs. The array is easily deployed by hand or with a small winch.

The Model DHA-7 production and performance is backed by Geometrics, now in its 40th year of knowledgeable and prompt customer support.

Tech Specs

Electrical

  • Hydrophone Sensor Type: Proprietary Polymer
  • Sensors per Group: One
  • Frequency response: 10 Hz to 10,000 Hz ± 1.0 dB
  • Capacitance: 5 nF at 22˚C
  • Sensitivity: -197 dB re 1 Volt per 1 μPa
  • Sensitivity with depth: < 1.0 dB over 400 m depth
  • Sensitivity with acceleration:< -70 dB re 1 Volt per g
  • Preamplifier Type: Ultra-low noise differential
  • Gain: 6 dB
  • Current: 10 mA per channel
  • Power: ±12V DC Model DHA Battery Pack on surface

Physical

Cable Type

  • Multi-conductor with polyurethane jacket
  • TerminationTopside: Y-type with one 61-socket connector (or 27-socket connector) and one 4-pin connector
  • Tail: 1-m (3.28-ft) long with stainless steel swivel and 6-kg (13.2-lb) weight
  • Maximum total length: 400 m (or 1,300 ft) (lead plus active section)
  • Strength member: Kevlar center stress core
  • Outside diameter: 13.5 mm (0.53 in)
  • Weight:
    • 12 channels: 0.12 kg per m (0.08 lbs per foot)
    • 24 channels: 0.15 kg per m (0.10 lbs per foot)
  • Bend radius: 12.7 cm (5 in)
  • Working load: 273 kg (600 lbs)
  • Breaking strength: 909 kg (2,000 lbs)

Active section

  • Channels: 12 or 24 standard; other counts available*
  • Group Interval: 1 to 5 m (or 3 to 15 ft) standard; other intervals available with a minimum of 0.5 m (or 18 in)
  • Outside diameter (hydrophone) 41.3 mm (1.63 in)
  • Length (hydrophone): 30.5 cm (12 in)
  • Weight (hydrophone): 0.16 kg (0.35 lbs)
  • Bend radius: 22.9 cm (9 in)

Environmental

  • Depth Operating Maximum: 400 m (or 1,300 ft)
  • Temperature Operating Range: -10˚C to +70˚C
  • Storage range: -40˚C to +70˚C

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