Expanding the Envelope: Demonstrating a 200ft Depth of Detection for an Ultradeep Azimuthal Resistivity Tool

This is a case study from the Norwegian continental shelf where ultra-deep resistivity tools were run in two wells, one passing over the other; this provided the opportunity to determine depth of detection for the tool.

Ultra-deep reading resistivity tools can delineate multiple resistivity boundaries. When these boundaries are a significant distance away, it is important to have confidence in both their position and the resistivity’s they represent. To gain more confidence in the apparent geology and fluid boundaries, it would be useful to obtain solid confirmation by mapping or logging those boundaries in a second well.

The two wells crossed near a section of a high-resistivity reservoir, which was detected by the ultra-deep resistivity measurements in both wells. This reservoir section was bounded above and below by low-resistivity zones and laterally by faults. This arrangement produced a distinctive shape that was easy to correlate between the two wells. By superimposing the two inverted resistivity profiles, it was demonstrated that the apparent shape of the reservoir, as observed from the two wells, was highly similar, indicating they showed the same structure.

The lower boundary was clearly visible in both sets of inversion results, approximately 200 below the upper well.