Downhole PV tests for bubble point pressure
First Claim
1. A method for determining a property of a fluid comprising:
- fitting a curve to a set of pressure versus volume data points for a fluid;
computing a second derivative of a function representing the curve; and
estimating a point where the slope of the second derivative is zero.
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Accused Products
Abstract
The present invention provides an objective bubble point pressure determination method enables new applications of downhole PV (Pressure Volume) test results such as in situ measurement of the bubble point pressure for use as a quality control parameter for sampling. The present invention provides a method and apparatus to fit data points to a curve and to smooth these points over an interval of N points. The derivative of the curve is determined to obtain peak acceleration. The peak acceleration represents the bubble point pressure. This bubble point pressure is verified by comparison to changes in fluid compressibility and visual observation of a pressure volume plot history.
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Citations
27 Claims
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1. A method for determining a property of a fluid comprising:
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fitting a curve to a set of pressure versus volume data points for a fluid;
computing a second derivative of a function representing the curve; and
estimating a point where the slope of the second derivative is zero. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for determining a property of a fluid comprising:
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fitting a set of curves to a set of pressure versus volume data points for the fluid;
computing the second derivative of a set of functions representing the set of curves; and
comparing the second derivative of the set of functions to determine the property of the fluid. - View Dependent Claims (13, 14, 15)
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16. A computer readable medium containing instructions that when executed by a computer perform a method for determining a property of a fluid comprising:
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fitting a curve to a set of pressure versus volume data points for a fluid;
computing a second derivative of a function representing the curve; and
estimating a point where the slope of the second derivative is zero. - View Dependent Claims (17, 18, 19)
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20. A computer readable medium containing instructions that when executed by a computer perform a method for determining a property of a fluid comprising:
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fitting a set of curves to a set of pressure versus volume data points for the fluid;
computing the second derivative of a set of functions representing the set of curves; and
comparing the second derivative of the set of functions to determine the property of the fluid. - View Dependent Claims (21, 22, 23)
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24. An apparatus for determining a property of a fluid comprising:
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a processor programmed to fit a curve to a set of pressure versus volume data points for a fluid, compute a second derivative of a function representing the curve; and
estimate a point where the slope of the second derivative is zero; and
an output device in data communication with the processors via which an estimate of the property is communicated. - View Dependent Claims (25, 26, 27)
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Specification