COMPARATIVE STUDY OF FRACTURES IN CORE AND BOREHOLE TELEVIEWER IN WELL VC-2B, VALLES CALDERA, NEW MEXICO

Abstract

Well VC-2B is a continuous core hole drilled in the Sulphur Springs area of the Valles caldera, New Mexico. It reached a temperature of 295o C at a total
depth of 5780 feet. Borehole televiewer logs are available for the depth interval of 704 feet to 910 feet where measured temperatures are about 140o to 145o C. This interval is the principal zone of lost circulation in the well and contains numerous fractures that can be identified as faults, mode I extensional fractures, hydrothermal breccias and completely and par-
tially sealed fractures. The zones responsible for the lost circulation can be identified in the core by the presence of drilling mud, lost circulation material and migrated fines derived from both the rock and drill
string. Analysis of fractures from the televiewer log of VC-2B shows that most of them strike to the northeast and dip steeply to the northwest, parallel to the Sulphur Creek fault zone.