Borehole Logging Method

Purpose: Borehole logging is a versatile technique for characterizing subsurface formations, providing detailed data on geological, hydrological, and structural properties. It is widely used in mineral exploration, environmental studies, and geotechnical assessments to enhance understanding of subsurface conditions.

Applications:

Geological Mapping: Gamma, resistivity, and spontaneous potential probes reveal geological changes, helping to identify formation layers and mineralized zones.

Contamination and Fluid Studies: Induction conductivity with gamma probes maps formation conductivity and potential contamination. Fluid conductivity and temperature logs identify flow zones and fracture locations.

Structural and Dimensional Analysis: Caliper probes assess borehole diameter changes and fracture distribution, supporting structural stability evaluations.

Technical Process: Borehole logging utilizes a range of probes to collect data on various parameters. Cross-hole IP/Resistivity surveys and Time-Domain EM surveys are also conducted using specialized electrodes and EM probes for detailed 3D subsurface mapping. Video logging offers visual confirmation of detected features, further aiding analysis.

Key Uses: Borehole logging is crucial for in-depth subsurface evaluation, providing insights into geological structures, fluid dynamics, and potential contamination pathways, essential across mineral, environmental, and construction sectors.

Boreholes can be surveyed with many types of probes:

• Caliper for mapping fractures and borehole diameter changes.
• Induction Conductivity used with gamma to map formation conductivity and potential contamination.
• Total Counts Gamma for mapping geologic changes.
• Single Point Resistivity for mapping geologic changes.
• Spontaneous Potential for mapping geologic changes.
• Fluid Conductivity useful for locating potential flow zones.
• Fluid Temperature also useful for locating fractures that might be flow sources.
• Heat Pulse Flowmeter is used to determine whether flow is up or down in the borehole at various depths, thus helping to locate flowing fractures.
• Optical Televiewer provides a high-resolution oriented 360 degrees image of the borehole. This is useful for mapping geologic variations and fractures.
• Acoustic Televiewer uses acoustic waves that highlight fractures and voids with colour images. It is also oriented and is used in conjunction with other logs to determine fluid flow contacts or fractures.

Borehole Time-Domain EM Surveys are also carried using 3D EM and Fluxgate probes.

The IP/Resistivity geophysical method use stainless steel and copper electrodes to acquire cross-hole survey data: Cross-hole IP/Resistivity Surveys for Gold & Voids

Video logs are also useful for further characterizing features detected within the borehole.

Seismic hydrophones placed inside a borehole with shots taken around the borehole can be used to determine direction to legacy wells and voids.