Methods to detect formation pressure
First Claim
1. A method of estimating a formation pressure during drawing of a fluid from a formation, comprising:
- drawing the fluid from the formation;
determining a fluid pressure at at least two different times during the drawing of the fluid from the formation; and
analyzing the fluid pressures using a higher-order pressurederivative with respect to time to estimate the formation pressure during the drawing of the fluid, wherein the higher-order pressure derivative with respect to time is greater than a second pressure derivative.
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Abstract
A method of determining a formation pressure during drawdown of a formation comprises sampling fluid from a formation using a downhole tool. A fluid sample pressure is determined at two different times during the drawdown. The fluid sample pressures are analyzed using a higher-order pressure derivative with respect to time technique to determine the formation pressure during the drawdown. Another method of determining a formation pressure during drawdown of a formation comprises sampling fluid from a formation using a downhole tool. A fluid sample pressure is determined at two different times during the drawdown. The fluid sample pressures are analyzed using at least two analysis techniques to each determine an estimate of the formation pressure during the drawdown.
47 Citations
23 Claims
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1. A method of estimating a formation pressure during drawing of a fluid from a formation, comprising:
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drawing the fluid from the formation; determining a fluid pressure at at least two different times during the drawing of the fluid from the formation; and analyzing the fluid pressures using a higher-order pressure derivative with respect to time to estimate the formation pressure during the drawing of the fluid, wherein the higher-order pressure derivative with respect to time is greater than a second pressure derivative. - View Dependent Claims (2, 5, 6, 7, 8, 9, 10, 11, 12)
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3. A method of estimating a formation pressure during drawing of a fluid from a formation, comprising:
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sampling fluid from a formation using a downhole tool; determining a fluid sample pressure at two different times during the drawdown; and analyzing the fluid sample pressures using at least two analysis techniques to each estimate a separate formation pressure during the drawdown, wherein the at least two analysis techniques are drawn from the group consisting of;
a first pressure derivative technique;
a higher-order pressure derivative technique;
a formation rate analysis technique;
a dp/dt-ratio technique; and
a stepwise drawdown technique. - View Dependent Claims (4)
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13. A method of testing fluid samples downhole, comprising:
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lowering a tool in a wellbore, the tool having a device to withdraw the fluid samples from a formation downhole, a pressure sensor for measuring pressure of the withdrawn fluid and a controller for controlling operation of the tool; drawing fluid samples from a formation downhole; measuring a fluid pressure at least two different times during the withdrawal of the fluid samples; and analyzing the fluid pressures using a higher-order pressure derivative with respect to time to determine the formation pressure during the withdrawal of the fluid samples, wherein the higher-order pressure derivative is greater than the second pressure derivative.
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14. A tool for use in a wellbore, comprising:
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a device adapted to drawdown fluid from a formation adjacent a wellbore; a pressure sensor that measures pressure of the fluid; and a controller that determines fluid pressure at at least two different times during drawing of the fluid and analyzes the fluid pressures using a higher-order pressure derivative with respect to time to estimate the formation pressure wherein the higher-order pressure derivative is greater than the second pressure derivative. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification