Downhole water chemistry sensing utilizing polymer matrix cartridge

A system for measuring ion concentration of a fluid downhole using a polymer matrix packaged in a cartridge comprising:

• an optical source configured to provide an illumination light through a first window;
• a cartridge disposed adjacent to the first window, the cartridge comprising:
• a bracket having a first opening;
• a retainer disposed within the first opening, the retainer formed of a porous material having pores sized to allow a fluid to flow therethrough, the retainer having a second opening;
• and
• a substrate disposed within the second opening, the substrate comprising a polymer matrix embedded with an ion-indicator, the substrate configured to interact with the fluid and to modify an optical characteristic of the substrate according to an ion concentration of the fluid;
• a detector configured to receive a sample light passing through the substrate and a second window, the second window disposed between the cartridge and the detector, wherein the illumination light optically interacts with the substrate to generate the sample light, the sample light indicative of the ion concentration of the fluid;
• and
• a controller configured to measure the ion concentration of the fluid based on the sample light.

A method for determining ion concentration of a fluid downhole using a polymer matrix packaged in a cartridge, the method comprising:

• disposing a cartridge within an optical path of a sensor, the cartridge comprising:
• a bracket having a first opening;
• a retainer disposed within the first opening, the retainer formed of a porous material having pores sized to allow a fluid to flow therethrough, the retainer having a second opening;
• and
• a substrate disposed within the second opening, the substrate comprising a polymer matrix embedded with an ion-indicator, the substrate configured to interact with the fluid and to modify an optical characteristic of the substrate according to an ion concentration of the fluid;
• illuminating the substrate;
• detecting a change in an optical characteristic of the substrate, the change indicative of the ion concentration of the fluid;
• and
• determining the ion concentration of the fluid.