Downhole Surveys - DHS Australia

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Geomole Borehole Radar

Borehole Radar is an electromagnetic subsurface imaging technique which provides high detailed continuous ore body and structural delineation information for mine planning and geotechnical applications.

DHS can do the acquisition with the GeoMole radar:

- Borehole radar research and development.
- Borehole radar tool manufacturing.
- Borehole radar data processing and interpretation software development – SeisWin.
- Borehole radar deployment, processing and interpretation training.
- Complete borehole radar solutions from problem description through to solution.

Services

GeoMole provides both technical and consultancy services. Borehole radar tools and software are available for lease to qualified personnel. Please contact info@geomole.com for more information.

Borehole Radar Technology

The GeoMole borehole radar can provide high resolution images to determine the continuity of target horizons up to 40 m from the borehole depending on the resistivity of the host rock.

GeoMole has two different radar tools available for surveys:

- The Monostatic or Iqua is a single probe radar that transmits and receives on the same antenna.

- The Bistatic or isiJula radar is longer at 5.5m and has a separate Transmitter (Tx) and Receiver (Rx) connected by a flexible or solid optical fiber spacer.

Radargram, showing how it is created from multiple single traces (one is shown in red)

Due to logistical and space constraints the Iqua radar is most often used; however the isiJula can also be used for specialised applications. It is important to note that due to the physics behind transmission the closest that the Iqua can ‘see’ a target is at 5m. Similarly, due to the physical configuration, the isiJula can only image targets further than 2 meters away.

Specification	Monostatic (Iqua)	Bistatic (IsiJula)
Length	1.65 m	5.5 m (1.65Tx + 2.0Spacer + 1.65Rx)
Diameter	32 mm – 42 mm	32 mm – 42 mm
Weight	3 Kg	8 Kg
Transmitted Frequency(Center)	10 -100Mhz (60Mhz)	10 – 100Mhz (40Mhz)
Storage Capacity	4hrs 30 min	4hrs 30min
Traces Capture Time	2 sec	2 sec
Optimal Deployment Speed	0.33 m per trace	0.33 m per trace
Download Method	Serial - Bluetooth	Serial - Bluetooth
Depth Rating	1000m ( 32 mm plastic housing) 3000m (36/42mm fiberglass housing)	1000m (32 mm plastic housing) 3000m (36/42 mm fiberglass housing)
Normal Range (min – max)	5-40m (varies with rock type)	2-40m (varies with rock type)
Maximum salinity	2000us/m	2000us/m
Sample Frequency	250Mhz	250Mhz
Primary Resolution	8-bit	8-bit
Battery Life	8 hrs – Survey or 12 hrs - Standby	8 hrs - Survey or 12hrs - Standby

Borehole radar radiation pattern

A radargram showing how it relates to 3D reality and modeled reality

Seiswin Software

SeisWin is a data analysis and interpretation package that provides interactive data processing and interpretation for borehole radar. The built-in utilities such as 1D and 2D filtering, special SVD filtering, event migration and common tangent line stacking allow the user to enhance the data quality and map the features from radar time sections onto the basemap for spatial presentation and validation. With prior geological knowledge, ambiguity associated with borehole radar can be eliminated.

SeisWin also provides a means for the interpretation and display of seismic and full waveform sonic data. Two and three-dimensional seismic data sets can be handled. The interpretation can involve interaction with a basemap window showing the locations of survey lines and relevant geological and other features. It allows the user to map features on the seismic section such as bad data zones and faults on to the base map so that the user can correlate them within the survey area.

Borehole design - for an optimal radar survey, radar signals shown in green

Radar Solutions

Borehole Radar has been applied successfully to the following areas:

Kimberlitic pipe delineation
Mapping potholes in the Bushveld platinum mines
Mineralised dyke and sill delineation
Imaging mineralised reefs ahead of mining
Massive nickel sulphide delineation
Mapping mineralised shear zones
Mapping structural information in shaft and geotech pilot boreholes
Tunnels and void detection

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