Systems and methods for downhole lithium sensing

A system for downhole lithium sensing, comprising:

• a plurality of ionophore-based sensor units disposed within a first subsurface reservoir, each ionophore-based sensor unit comprising a housing in which a lithium ionophore sensor, a wireless communication unit, and a microprocessor connected with the lithium ionophore sensor are disposed;
• and
• a computing unit located outside the first subsurface reservoir, the computing unit in wireless communication with the plurality of ionophore-based sensor units,
• wherein each ionophore-based sensor unit is configured to:
• collect a sample of reservoir brine from the first subsurface reservoir;
• determine a local concentration value of ionic lithium in the sample;
• and
• transmit the local concentration value to the computing unit, and
• wherein the computing unit is configured to estimate a total concentration value of ionic lithium in the first subsurface reservoir from the local concentration values.