Prediction of percentage levels of gases that are undetectable via optical absorption measurements

A method comprising:

• disposing a fluid sampling tool within a wellbore;
• drawing fluid from a formation within the wellbore, within which the fluid sampling tool is disposed, using a probe;
• detecting raw data relating to optical properties of the fluid using a spectrometer, wherein the raw data relating to the optical properties of the fluid comprises optical absorbance at a plurality of wavelengths;
• receiving, by a controller, the raw data relating to optical properties of the fluid from the spectrometer, wherein the controller comprises at least one processor configured to execute coded instruction stored in a memory of the controller;
• predicting, by the controller, percentage levels of one or more components in the fluid based at least in part on the raw data relating to the optical properties of the fluid, wherein the one or more components comprise at least one gas component without an optical signature in the near infrared spectrum;
• predicting a partial mass density of the fluid based at least in part on the raw data relating to the optical properties of the fluid;
• predicting an ideal mass density of the fluid based on an assumption that the fluid contains only hydrocarbons and carbon dioxide;
• comparing the partial mass density to the ideal mass density to determine whether the one or more components comprise one or more non-hydrocarbon components based on a percentage difference between the partial mass density and the ideal mass density;
• and
• determining a mole fraction of the one or more non-hydrocarbon components based on the percentage difference.

A fluid sampling system, comprising:

• a fluid sampling tool comprising:
• a probe configured to draw a fluid from a formation within which the fluid sampling tool is disposed during an oil and gas well operation;
• and
• a spectrometer configured to detect raw data relating to optical properties of the fluid, wherein the raw data relating to the optical properties of the fluid comprises optical absorbance at a plurality of wavelengths;
• and
• a controller comprising at least one processor configured to execute coded instructions stored in memory of the controller, wherein the coded instructions, when executed by the at least one processor, cause the processor to:
• receive the raw data relating to the optical properties of the fluid from the spectrometer;
• predict percentage levels of one or more components in the fluid based at least in part on the raw data relating to the optical properties of the fluid, wherein the one or more components comprise at least one gas component without an optical signature in the near infrared spectrum;
• predict compositions of the one or more components in the fluid;
• predict data relating to the optical properties of the fluid, pressure of the fluid, and temperature of the fluid based at least in part on the compositions of the one or more components of the fluid, pressure of the fluid, and temperature of the fluid;
• compare the predicted data relating to the optical properties of the fluid to the raw data relating to the optical properties of the fluid to determine whether the one or more components comprise one or more non-hydrocarbon components based on a percentage difference between the predicted data relating to the optical properties of the fluid and the raw data relating to the optical properties of the fluid;
• and
• determine a mole fraction of the one or more non-hydrocarbon components based on the percentage difference.

A method comprising:

• disposing a fluid sampling tool within a wellbore;
• drawing fluid from a formation within the wellbore, within which the fluid sampling tool is disposed, using a probe;
• detecting raw data relating to optical properties of the fluid using a spectrometer, wherein the raw data relating to the optical properties of the fluid comprises optical absorbance at a plurality of wavelengths;
• receiving, by a controller, the raw data relating to optical properties of the fluid from the spectrometer, wherein the controller comprises at least one processor configured to execute coded instruction stored in a memory of the controller;
• predicting, by the controller, percentage levels of one or more components in the fluid based at least in part on the raw data relating to the optical properties of the fluid, wherein the one or more components comprise at least one gas component without an optical signature in the near infrared spectrum;
• predicting compositions of the one or more components in the fluid;
• predicting data relating to the optical properties of the fluid, pressure of the fluid, and temperature of the fluid based at least in part on the compositions of the one or more components of the fluid, pressure of the fluid, and temperature of the fluid;
• comparing the predicted data relating to the optical properties of the fluid to the raw data relating to the optical properties of the fluid to determine whether the one or more components comprise one or more non-hydrocarbon components based on a percentage difference between the predicted data relating to the optical properties of the fluid and the raw data relating to the optical properties of the fluid;
• and
• determining a mole fraction of the one or more non-hydrocarbon components based on the percentage difference.