Processes and systems for monitoring one or more gases dissolved in a liquid

A process for calibrating a Raman system, comprising:

• preparing a mixture comprising water and at least one gas at a pressure of about 14.7 psi-absolute to about 2,000 psi-absolute, wherein the at least one gas is dissolved in the water, and wherein the mixture is at thermodynamic equilibrium;
• flowing the mixture through a flowline and into an inlet of a sample cell, wherein degassing in the flowline is substantially avoided by increasing the pressure by at least 1 psi-absolute above the pressure the mixture of water and the at least one gas was prepared;
• flowing the mixture through the sample cell, wherein at least a portion of the mixture flows past an optical window such that the mixture is viewable within the sample cell through the optical window;
• recovering the mixture from an outlet of the sample cell;
• emitting an electromagnetic radiation signal into the sample cell through the optical window for at least a portion of the time the mixture is viewable through the optical window;
• contacting the mixture with the electromagnetic radiation signal within the sample cell;
• directing a scattered electromagnetic radiation signal comprising Rayleigh scattering and Raman scattering emitted from the sample cell through the optical window into a filter to remove at least a portion of the Rayleigh scattering to produce a primarily Raman scattering signal;
• directing the primarily Raman scattering signal to a detector to detect a Raman signal indicating the presence of the at least one gas dissolved in the water;
• and
• correlating the Raman signal to a dissolved concentration of the at least one gas with a thermodynamic model for the mixture of water and the at least one gas.