DHA-7
from Geometrics

The 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.

DHA-7 with Geode Seismograph.
DHA-7 with Geode Seismograph.

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 0.5 to 5 m and a total cable length of up to 400 m (1,312 ft). The cable is terminated topside with suitable connectors to mate with the seismograph and a 12VDC rechargeable power supply. Custom group intervals and multiborehole configurations are also available to tailor the system to meet your needs. The array is easily deployed by hand.

Applications

  • 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

    Features

  • 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

Product Dimensions

Physical Dimensions (L x W x H) Weight
DHA-7 (instrument only) depends on hydrophone int x 41.3mm x 41.3mm 0.15kg/m

Technical Specifications

Hydrophone Sensor Type: Proprietary Polymer
Channels: 12 or 24.
Hydrophone Interval: 1-5m
Sensors per Group: One.
Frequency Response: 10 Hz to 10,000 Hz ± 1.0 dB.
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
Power: ±12V DC Model DHA Battery Pack on surface.
Maximum total length: 400 m, lead plus active section.
Strength member: Kevlar center stress core.
Bend Radius: 12.7 cm
Working Load: 273 kg
Breaking strength: 909 kg
Temperature Operating Range: -10˚C to +70˚C

Shipping

Contents Dimensions (L x W x H) Weight
Reel 1
DHA-7
75cm x 75cm x 52cm 55kg
Case1
Tail weight, battery, cables.
50cm x 40cm x 40cm 25kg
Shipping Notes:

If dispatched with a Geode seismograph then the system will be collated onto a pallet. The courier will require a fork lift or tailgate flit.

Data Sheet