Methods and apparatus for downhole fluids analysis
First Claim
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1. A method of determining gas-oil ratio of a formation fluid comprising:
- a) subjecting the fluid to spectroscopic analysis at at least two wavelengths, one of which is sensitive to the presence of gas and the other of which is sensitive to the presence of oil and generating response data;
b) determining a response matrix {circumflex over (B)} from the response of gas at the two wavelengths and the response of oil at the two wavelengths;
c) determining a signal response vector {right arrow over (S)} at the two wavelengths;
d) calculating a mass fraction vector {right arrow over (m)} of a gas-oil mixture according to the relationship {right arrow over (S)}={circumflex over (B)}{right arrow over (m)}; and
e) determining the gas-oil ratio from the mass fraction vector.
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Abstract
A method of determining GOR comprising subjecting a fluid to spectroscopic analysis at a first wavelength sensitive to gas and a second wavelength sensitive to oil, determining a response matrix for the contribution of gas at the first and second wavelengths and the contribution of oil at the first and second wavelengths, determining a signal response vector and the two wavelengths, calculating a mass fraction vector from the response matrix and the signal response vector and using the mass fraction vector to determine GOR.
129 Citations
23 Claims
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1. A method of determining gas-oil ratio of a formation fluid comprising:
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a) subjecting the fluid to spectroscopic analysis at at least two wavelengths, one of which is sensitive to the presence of gas and the other of which is sensitive to the presence of oil and generating response data;
b) determining a response matrix {circumflex over (B)} from the response of gas at the two wavelengths and the response of oil at the two wavelengths;
c) determining a signal response vector {right arrow over (S)} at the two wavelengths;
d) calculating a mass fraction vector {right arrow over (m)} of a gas-oil mixture according to the relationship {right arrow over (S)}={circumflex over (B)}{right arrow over (m)}; and
e) determining the gas-oil ratio from the mass fraction vector. - View Dependent Claims (7, 8, 9, 10)
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- 2. A method as claimed in claim l,wherein the response matrix {circumflex over (B)} comprises a first column comprising the spectroscopic response of gas at each of the two wavelengths, and a second column comprising the spectroscopic response of oil at each of the two wavelengths.
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11. Apparatus for determining gas-oil ratio of a fluid obtained from a formation surrounding a borehole comprising:
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a) a tool body which can be located in the borehole and establish fluid communication with the formation so as to withdraw a sample of fluid therefrom;
b) a spectroscopy module located in the tool body for subjecting the fluid sample to spectroscopic analysis at at least two wavelengths, one of which is sensitive to the presence of gas and the other of which is sensitive to the presence of oil and generating response data;
c) means for determining the gas-oil ratio of the sample which calculates a mass fraction vector {right arrow over (m)} of a gas-oil mixture according to the relationship {right arrow over (S)}={circumflex over (B)}{right arrow over (m)}, wherein {right arrow over (S)} is a signal response vector at the two wavelengths, {circumflex over (B)} is a response matrix formed from the response of gas at the two wavelengths and the response of oil at the two wavelengths; and
determines the gas-oil ratio from the mass fraction vector {right arrow over (m)}.- View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A method of analysing fluids from an underground formation using a spectrometer having a light source, a measurement cell and a detector, the method comprising:
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a) determining a temperature dependency curve for source data made from measurements made by the detector of light passing directly from the source;
b) determining a temperature dependency curve for measure data made from measurements made by the detector of light passing through the measurement cell;
c) measuring the response of the detector to light passing through the measurement cell when filled with fluid; and
d) analysing the fluid based on the measured response and the determined temperature dependency curves. - View Dependent Claims (19)
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20. Apparatus for analysing fluids from a formation surrounding a borehole, comprising:
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a) a tool body for location in the borehole;
b) means for establishing fluid communication with the formation;
c) a flow line in the tool body for flowing fluid samples from the formation; and
d) first and second optical analysis modules in the tool body and connected by a flow line, each module capable of making optical measurements on the fluids in the flow line. - View Dependent Claims (21)
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22. A method of analyzing fluids from an underground formation using a spectrometer having a light source, a flow line including a measurement cell and a detector, the method comprising:
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a) making spectroscopic measurements of fluid in the measurement cell at a wavelength responsive to the presence of alkanes; and
b) using the measurements to indicate the presence of gas in the flow line. - View Dependent Claims (23)
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Specification