Downhole fluid sampling system with hydraulic actuation

A method comprising:

• receiving, by a sampling system of a downhole tool deployed in a wellbore, a flow of formation fluid from the wellbore;
• collecting, by a first sampling chamber of a sampling unit positioned in the sampling system, a first sample from the flow of formation fluid, the sampling unit defining a set of sampling chambers including the first sampling chamber and a second sampling chamber;
• advancing, by a piston of the sampling system actuating on hydraulic fluid to displace at least a portion of the hydraulic fluid, the sampling unit by a predefined distance from a first position associated with the first sampling chamber to a second position associated with the second sampling chamber;
• and
• subsequent to advancing the sampling unit, collecting, by the second sampling chamber, a second sample from the flow of formation fluid.

A downhole tool comprising:

• a tool string positionable downhole in a wellbore;
• and
• a sampling system couplable to the tool string, the sampling system comprising:
• a sampling unit positionable to receive a flow of formation fluid from the wellbore, the sampling unit defining a set of sampling chambers that includes:
• a first sampling chamber positionable in the sampling unit to collect a first sample from the flow of formation fluid when the sampling unit is positioned at a first position in the sampling system;
• and
• a second sampling chamber positionable in the sampling unit to collect a second sample from the flow of formation fluid when the sampling unit is positioned at a second position in the sampling system;
• and
• a piston actuatable on hydraulic fluid of the sampling system to displace at least a portion of the hydraulic fluid to cause the sampling unit to advance by a predefined distance from the first position associated with the first sampling chamber to the second position associated with the second sampling chamber.