| Abstract |
The combined depths of two CSDP tests at Valles Calder, New Mexico, give researchers access to 1386 m (4545 ft) of continuous core form one of the most famous quaternary caldera in the world. VC-1 and VC-2A were both drilled near the ring faults of the Valles Caldera. A mineral type exploration rig utilizing a continuous coring, wire line retrievable core system was used for the drilling. Because of the close annular space (about 0.2 in), and the adverse downhole environment of temperature, H2S, CO2, torque, loss of returns, and sloughing sections close control of the drilling fluid was required. IN spite of the hostile environment encountered, 95-100% core recovery was accomplished by utilizing a low solids, liquid anionic copolymer drilling fluid. Hole advancement was 1/2 to 1 1/2 hour per 10 foot (3m) core tube. Down time was minimal (less than 4%). Actual coring occupied about 60% of the total time. |