Reduced contamination sampling

A method for obtaining fluid from a subsurface formation penetrated by a wellbore, comprising:

• positioning a formation testing apparatus within the wellbore, the testing apparatus comprising a sample chamber having a floating piston slidably positioned therein so as to define a sample cavity and a buffer cavity;
• establishing fluid communication between the apparatus and the formation;
• inducing movement of fluid from the formation through a main flowline in the apparatus;
• diverting fluid from the main flowline into the sample cavity via a first flowline;
• discharging fluid from the sample cavity via a second flowline whereby fluid is flushed from the sample cavity;
• and
• terminating the discharge of fluid from the sample cavity whereby a sample is collected in the sample cavity.

A downhole sampling tool positionable in a wellbore penetrating a subterranean formation, comprising:

• a probe assembly for establishing fluid communication between the apparatus and the formation when the apparatus is positioned in the wellbore;
• a pump assembly for drawing fluid from the formation into the apparatus via said probe assembly;
• a main flowline extending through the downhole tool for communicating fluid obtained from the formation through the downhole tool;
• a main valve in the main flowline movable between a closed and an open position, the valve defining a first portion and a second portion of the main flowline;
• and
• a sample module for collecting a sample of the formation fluid drawn from the formation by said pumping assembly, said sample module comprising:
• at least one sample chamber have a slidable piston therein defining a sample cavity and a buffer cavity, the sample cavity in selective fluid communication with the first portion of the main flowline via a first flowline and in selective fluid communication with the second portion of the main flowline via a second flowline;
• wherein when the main valve is in the closed position, fluid communication is selectively established between the sample cavity and one of the first portion of the main flowline, the second portion of the main flowline and combinations thereof.