Model DHA-7

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

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