Deep Televiewer investigations for a proposed open pit copper-gold mine

August 11, 2026

The Situation

As part of a feasibility study for the development of the US$2.37 Billion proposed open pit copper-gold mine on the Island of Mindanao in the Philippines, a series of deep boreholes were drilled to better model some of the worlds largest undeveloped copper-gold deposits.

Technical Approach

As part of this ground Investigation, a number of the boreholes were scanned with Advanced Logic Technologies Optical and Acoustic televiewers to better understand the Porphyry deposits and map any defect orientations and lineation’s within the diorites and volcanic geology of the site. A typical vertical sample interval of 1-2 mm was used, with a sample taken every 1° around the 360° image.

Figure 1- Televiewer logging at the Kingking site (Credit: RDCL).

Borehole depths ranged from 95 – 447 m across the site, and all were inclined between 70° - 80°. This posed on-site challenges in relation to centralisation of the tools (Televiewer data is critical to be well centralised in order to capture undistorted, high quality images of the borehole wall). Metallic, bow-string centralisers were used to ensure all tools were run centralised.

Due to the unstable nature of the volcanoclastic geology, all boreholes were logged in multiple open-hole sections. This is where casing was pulled up in stages, and stable sections are logged individually to reduce the risk of open hole section’s collapsing and leading to data loss. The televiewer imagery from each open hole section of the borehole is then depth-matched with each other and with core information, and merged into one single log. The 400 m+ boreholes were logged in 26-28 runs of 10-40 m sections.

Outcomes

A high resolution, digital & orientated image of the rock wall was able to be collected in each of the boreholes for this investigation. Key fracture zones were able to be identified and cross-referenced with recovered core. Using the televiewer tools in-built magnetometer and inclinometer’s, all imagery was orientated to magnetic north, but was able to be corrected for true north. This effectively gave a digital orientated image, with true dip direction and azimuths being able to be calculated for all identified defect features.

All data processing was undertaken in WellCAD. Using WellCAD’s advanced image interpretation module, further calculations were able to be determined, including;

· Stereonet (Polar Projection) Plot

· Rock Quality Designation

· Acoustic Impedance

· Rose Diagram

· Histogram

Figure 2- Stereonet projection plot from a typical 250 m hole.

Summary

Within the 400 m+ boreholes, over 1,500 defect features were able to be identified within each borehole, providing an unprecedented level of detail to be able to be extracted from the drilling program.

Recovered core information, mostly borehole logs and core photos, were cross-referenced during televiewer defect interpretations. This information highlighted a number of previously classified defects and fracture zones seen in the recovered core, but not in the televiewer logs. This differentiated a number of defects that are likely to be drilling induced or related, and not indeed geological in nature. This led to a revision of the previous interpretation to result in a more accurate geological model of each borehole.

Figure 3- Acoustic televiewer example with imported unoriented core photos.