PETROLEUM-FLUID PROPERTY PREDICTION FROM GAS CHROMATOGRAPHIC ANALYSIS OF ROCK EXTRACTS OR FLUID SAMPLES
First Claim
1. A method of analyzing reservoir fluid property comprising:
- a) obtaining a rock extract or fluid sample from a subterranean reservoir;
b) analyzing the rock extract or fluid sample by gas chromatography to provide a gas chromatogram;
c) calculating chromatographic peak area for three or more alkanes in the gas chromatogram;
d) selecting a representative series of three or more alkane peaks for analysis;
e) optionally, normalizing the alkane peak areas across the representative series;
f) optionally, converting the chromatographic peak areas of the selected series to mole percent or weight percent;
g) obtaining a plot of the concentration in terms of peak area, mole percent or weight percent, against carbon number or molecular weight;
h) fitting an equation to plotted concentrations obtained from (g);
i) determining goodness of fit (R2) for the equation to the plotted peaks;
j) re-selecting the representative series of alkane peaks and repeating (e), (f), (g), (h), (i) and (j) as needed to obtain suitable goodness of fit;
k) identifying calibration petroleum sample or samples with similar plot; and
l) assigning one or more fluid properties from the calibration petroleum sample or samples to the rock extract or fluid sample with unknown property.
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Abstract
This method allows for prediction of subsurface fluid properties (e.g., phase or API gravity) using gas chromatogram data of a small-volume extract. Small volume equates to microliter scale volume (or milligram scale weight) from a subsurface rock sample, where a fluid test may not be available for analysis. The method may also be applied to petroleum liquid samples where drilling fluid or other contaminants preclude accurate direct property measurement. Gas chromatographic data is calibrated to measured petroleum properties; preferably local oils from the same petroleum system, however, a general global calibration can also be used.
6 Citations
19 Claims
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1. A method of analyzing reservoir fluid property comprising:
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a) obtaining a rock extract or fluid sample from a subterranean reservoir; b) analyzing the rock extract or fluid sample by gas chromatography to provide a gas chromatogram; c) calculating chromatographic peak area for three or more alkanes in the gas chromatogram; d) selecting a representative series of three or more alkane peaks for analysis; e) optionally, normalizing the alkane peak areas across the representative series; f) optionally, converting the chromatographic peak areas of the selected series to mole percent or weight percent; g) obtaining a plot of the concentration in terms of peak area, mole percent or weight percent, against carbon number or molecular weight; h) fitting an equation to plotted concentrations obtained from (g); i) determining goodness of fit (R2) for the equation to the plotted peaks; j) re-selecting the representative series of alkane peaks and repeating (e), (f), (g), (h), (i) and (j) as needed to obtain suitable goodness of fit; k) identifying calibration petroleum sample or samples with similar plot; and l) assigning one or more fluid properties from the calibration petroleum sample or samples to the rock extract or fluid sample with unknown property. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of analyzing reservoir fluid property comprising:
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a) obtaining a rock extract or fluid sample from a subterranean reservoir; b) analyzing the rock extract or fluid sample by gas chromatography to provide a gas chromatogram; c) calculating chromatographic area for three or more alkane pseudocomponents in the gas chromatogram; d) selecting a representative series of three or more pseudocomponent areas for analysis; e) optionally, normalizing the pseudocomponent peak areas across the representative series; f) optionally, converting the pseudocomponent peak areas of the selected series to mole percent or weight percent; g) obtaining a plot of the concentration in terms of pseudocomponent peak area, mole percent or weight percent against carbon number or molecular weight; h) fitting an equation to plotted concentrations obtained from (g); i) determining goodness of fit (R2) for the equation to the pseudocomponent areas; j) re-selecting the representative series of pseudocomponent areas and repeating (e), (f), (g), (h), (i) and (j) as needed to obtain suitable goodness of fit; k) identifying a calibration petroleum sample with similar plot; and l) assigning one or more fluid properties from the calibration petroleum sample to the rock extract or fluid sample with unknown properties. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of analyzing reservoir fluid property comprising:
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a) obtaining a contaminated, degraded or evaporated rock extract or fluid sample from a subterranean reservoir; b) analyzing the contaminated, degraded or evaporated rock extract or fluid sample by gas chromatography to provide a gas chromatogram; c) calculating chromatographic area for three or more alkane areas in the gas chromatogram; d) selecting a representative series of three or more alkane areas for analysis; e) optionally, normalizing the alkane peak areas across the representative series; f) optionally, converting the chromatographic peak areas of the selected series to mole percent or weight percent; g) obtaining a plot of the concentration in terms of peak area, mole percent or weight percent against carbon number or molecular weight; h) fitting an equation to plotted concentrations obtained from (g); i) determining goodness of fit (R2) for the equation to the plotted peaks; j) re-selecting the selected series of alkane areas and repeating (e), (f), (g), (h), (i) and (j) as needed to obtain suitable goodness of fit; k) identifying a calibration petroleum sample with similar plot; and l) assigning one or more fluid properties from the calibration petroleum sample to the contaminated, degraded or evaporated rock extract or fluid sample with unknown property. - View Dependent Claims (16, 17, 18, 19)
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Specification