IVZ - General Discussion, page-1217

Roch doesn't understand the basics of wireline formation testing.

When you conduct a pretest with a tool like the MDT you're flowing formation fluid from a point in the bore into a small pretest chamber (20cc). If the formation is low perm you'd reduce your drawdown volume to less than 20cc. You're also drawing fluid in from a small radius around the well bore.

During a flow test you're flowing a much larger section of the well bore into the bore and to surface. A flow test has a much larger radius of investigation than an MDT tool and you're drawing down and then shutting in the tool to let the reservoir recover to original pressure over much longer periods than with an MDT pretest (MDT pretest - minutes, flow test - hours).