Downhole electrochemical fluid sensor and method of using same

A system for sensing downhole parameters of a downhole fluid in a wellbore penetrating a subterranean formation, the system comprising:

• a downhole tool deployable into the wellbore;
• and
• an electrochemical fluid sensor comprising:
• a sensing portion in the downhole tool, comprising:
• a sensor body;
• a plurality of electrodes positioned within the sensor body;
• and
• part of a mediator flowline to circulate a sensing solution about the plurality of electrodes, the sensing solution comprising a mediator reactive to target chemicals;
• and
• a fluid portion positionable outside the downhole tool and connected to the sensing portion, the fluid portion comprising:
• part of the mediator flowline;
• and
• a gas permeable membrane positioned in the housing to fluidly isolate the downhole fluid from the sensing solution, the gas permeable membrane permitting a passage of gas to the sensing solution;
• and
• wherein the plurality of electrodes measures a change in an electrical current based on electrochemical reaction by the sensing solution whereby concentration of the downhole parameters of the target chemicals may be determined based on the measured change.