Process-based approach for the detection of CO2 injectate leakage
View Patent ↗The present invention includes a method for distinguishing between a natural source of deep gas and gas leaking from a CO 2 storage reservoir at a near surface formation comprising: obtaining one or more surface or near surface geological samples; measuring a CO 2 , an O 2 , a CH 4 , and an N 2 level from the surface or near surface geological sample; determining the water vapor content at or above the surface or near surface geological samples; normalizing the gas mixture of the CO 2 , the O 2 , the CH 4 , the N 2 and the water vapor content to 100% by volume or 1 atmospheric total pressure; determining: a ratio of CO 2 versus N 2 ; and a ratio of CO 2 to N 2 , wherein if the ratio is greater than that produced by a natural source of deep gas CO 2 or deep gas methane oxidizing to CO 2 , the ratio is indicative of gas leaking from a CO 2 storage reservoir.
1. A process-based method of detecting a CO 2 gas leak in a deep geologic gas storage reservoir, the method comprising:
constructing a gas sampling station in a vadose zone proximal to the deep geologic gas storage reservoir;
measuring a CO 2 level in the vadose zone using one or more gas analyzers sampling gas from the vadose zone through the gas sampling station;
measuring an O 2 level in the vadose zone using one or more gas analyzers sampling gas from the vadose zone through the gas sampling station;
measuring a CH 4 level in the vadose zone using one or more gas analyzers sampling gas from the vadose zone through the gas sampling station;
measuring a N 2 level in the vadose zone using one or more gas analyzers sampling gas from the vadose zone through the gas sampling station;
determining a H 2 O vapor level in the vadose zone;
determining an Ar level in the vadose zone;
computing a normalized CO 2 level, a normalized O 2 level, a normalized CH 4 level, a normalized N 2 level, a normalized Ar level, and a normalized H 2 O vapor level using the CO 2 level, the O 2 level, the CH 4 level, the N 2 level, the Ar level, and the H 2 O vapor level, wherein a normalized level corresponds to a concentration of a gas referenced to 100% by volume or to 1 atmosphere total pressure;
determining a first relationship representing the normalized O 2 level as a function of the normalized CO 2 level;
generating a comparison of the first relationship with a second relationship representing O 2 levels as a function of CO 2 levels for respiration processes;
determining, using the comparison, that the first relationship is indicative of the normalized CO 2 level for the normalized O 2 level being greater than that expected for respiration, thereby detecting that CO 2 gas is being added to the vadose zone from an exogenous deep source;
generating a second comparison of the first relationship with a third relationship representing O 2 levels as a function of CO 2 levels from CH 4 oxidation processes;
determining, using the second comparison, that the first relationship is indicative of the normalized CO 2 level for the normalized O 2 level being greater than that expected from CH 4 oxidation, thereby confirming that CO 2 gas is being added to the vadose zone from the exogenous deep source; and
indicating that CO 2 gas is leaking from the deep geologic gas storage reservoir.
2. The method of claim 1 , wherein determining the first relationship includes generating a plot of the normalized O 2 level versus the normalized CO 2 level.
3. The method of claim 2 , wherein generating the comparison includes showing a curve on the plot representing the second relationship.
4. The method of claim 1 , wherein determining the first relationship includes generating a plot of the normalized O 2 level versus the normalized CO 2 level, and wherein generating the second comparison includes showing a curve on the plot representing the third relationship.
5. The method of claim 1 , further comprising:
determining a third relationship representing the normalized CO 2 level as a function of the normalized N 2 level;
generating a second comparison of the third relationship with a normalized atmospheric N 2 level; and
determining, using the second comparison, that the normalized N 2 level is less than the normalized atmospheric N 2 level, thereby detecting that CO 2 gas is being added to the vadose zone from an exogenous deep source.
6. The method of claim 5 , wherein determining the third relationship includes generating a second plot of the normalized CO 2 level versus the normalized N 2 level.
7. The method of claim 6 , wherein generating the second comparison includes showing a line on the second plot representing the normalized atmospheric N 2 level.
8. The method of claim 1 , further comprising:
determining a normalized N 2 /O 2 level using the normalized N 2 level and the normalized O 2 level;
determining a third relationship of the normalized CO 2 level as a function of the normalized N 2 /O 2 level;
generating a second comparison of the third relationship with a fourth relationship representing CO 2 levels as a function of N 2 /O 2 levels for respiration or methane oxidation; and
determining, using the second comparison, that the third relationship is indicative of the normalized CO 2 level for the normalized N 2 /O 2 level being greater than that expected for respiration or CH 4 oxidation, thereby detecting that CO 2 gas is being added to the vadose zone from an exogenous deep source.
9. The method of claim 8 , wherein determining the third relationship includes generating a second plot of the normalized CO 2 level versus the normalized N 2 /O 2 level.
10. The method of claim 9 , wherein generating the second comparison includes showing a curve on the second plot representing the fourth relationship.
11. A process-based method of detecting a natural source of CO 2 gas proximal to a deep geologic gas storage reservoir, the method comprising:
constructing a gas sampling station in a vadose zone proximal to the deep geologic gas storage reservoir;
measuring a CO 2 level in the vadose zone using one or more gas analyzers sampling gas from the vadose zone through the gas sampling station;
measuring an O 2 level in the vadose zone using one or more gas analyzers sampling gas from the vadose zone through the gas sampling station;
measuring a CH 4 level in the vadose zone using one or more gas analyzers sampling gas from the vadose zone through the gas sampling station;
measuring a N 2 level in the vadose zone using one or more gas analyzers sampling gas from the vadose zone through the gas sampling station;
determining a H 2 O vapor level in the vadose zone;
determining an Ar level in the vadose zone;
computing a normalized CO 2 level, a normalized O 2 level, a normalized CH 4 level, a normalized N 2 level, a normalized Ar level, and a normalized H 2 O vapor level using the CO 2 level, the O 2 level, the CH 4 level, the N 2 level, the Ar level, and the H 2 O vapor level, wherein a normalized level corresponds to a concentration of a gas referenced to 100% by volume or to 1 atmosphere total pressure;
determining a first relationship representing the normalized O 2 level as a function of the normalized CO 2 level;
generating a comparison of the first relationship with a second relationship representing O 2 levels as a function of CO 2 levels for respiration processes;
determining, using the comparison, that the first relationship is indicative of the normalized CO 2 level for the normalized O 2 level being smaller or about equal to that expected for respiration, thereby detecting that CO 2 gas is being added to the vadose zone by a natural source;
generating a second comparison of the first relationship with a third relationship representing O 2 levels as a function of CO 2 levels from CH 4 oxidation processes;
determining, using the second comparison, that the first relationship is indicative of the normalized CO 2 level for the normalized O 2 level being smaller than or about equal to that expected from CH 4 oxidation, thereby confirming that CO 2 gas is being added to the vadose zone by the natural source; and
indicating that CO 2 gas present in the vadose zone is from a natural source.
12. The method of claim 11 , further comprising:
identifying the natural source as biological respiration.
13. The method of claim 11 , wherein determining the first relationship includes generating a plot of the normalized O 2 level versus the normalized CO 2 level.
14. The method of claim 13 , wherein generating the comparison includes showing a curve on the plot representing the second relationship.
15. The method of claim 11 , further comprising:
identifying the natural source as CO 2 from CH 4 oxidation.
16. The method of claim 11 , wherein determining the first relationship includes generating a plot of the normalized O 2 level versus the normalized CO 2 level, and wherein generating the second comparison includes showing a curve on the plot representing the third relationship.
17. The method of claim 11 , further comprising:
determining a third relationship representing the normalized CO 2 level as a function of the normalized N 2 level;
generating a second comparison of the third relationship with a normalized atmospheric N 2 level; and
determining, using the second comparison, that the normalized N 2 level is about equal to the normalized atmospheric N 2 level, thereby detecting that CO 2 gas is being added to the vadose zone from a natural source.
18. The method of claim 17 , wherein determining the third relationship includes generating a second plot of the normalized CO 2 level versus the normalized N 2 level.
19. The method of claim 18 , wherein generating the second comparison includes showing a line on the second plot representing the normalized atmospheric N 2 level.
20. The method of claim 11 , further comprising:
determining a normalized N 2 /O 2 level using the normalized N 2 level and the normalized O 2 level;
determining a third relationship of the normalized CO 2 level as a function of the normalized N 2 /O 2 level;
generating a second comparison of the third relationship with a fourth relationship representing CO 2 levels as a function of N 2 /O 2 levels for respiration or methane oxidation; and
determining, using the second comparison, that the third relationship is indicative of the normalized CO 2 level for the normalized N 2 /O 2 level being about equal to or less than that expected for respiration or CH 4 oxidation, thereby detecting that CO 2 gas is being added to the vadose zone from a natural source.
21. The method of claim 20 , wherein determining the third relationship includes generating a second plot of the normalized CO 2 level versus the normalized N 2 /O 2 level and wherein generating the second comparison includes showing a curve on the second plot representing the fourth relationship.