Ann: Testing Update , page-16

Veeone - the reason why PB2 ended so abruptly is because of the bentonite clays drilling towards Leadville - they, at times are undrillable - you drill through them - well basically wash them and they then close back over your drill string increasing the friction pull - forever back reaming to ensure the torque is kept to within limitations of the strength of your string or you HP pull. This is supposedly why PB2 was pulled - too risky for the contractor to continue to drill into!