Early evaluation by fall-off testing
First Claim
1. A method of testing a zone of interest in subsurface formation intersected by a well, comprising:
- (a) providing a column of fluid in said well, said column of fluid having an overbalanced hydrostatic pressure at said subsurface formation greater than a formation pressure of said subsurface formation;
(b) running a testing string into said well, said testing string including a packer, a pressure monitor and a closure tool arranged to close a bore of said testing string;
(c) shutting in said subsurface formation by setting said packer and closing said bore of said testing string with said closure tool and thereby initially trapping said overbalanced hydrostatic pressure of said column of fluid in said well below said packer; and
(d) after step (c), monitoring a pressure fall-off in said well below said packer.
3 Assignments
0 Petitions
Accused Products
Abstract
Early evaluation testing of a subsurface formation is provided by monitoring pressure fall-off in the formation. This is accomplished by providing a column of fluid in the well having an overbalanced, hydrostatic pressure at the subsurface formation greater than a natural formation pressure of the subsurface formation. A testing string is run into the well, and the testing string includes a packer, a pressure monitor and a closure tool arranged to close a bore of the testing string. The formation is shut in by setting the packer and closing the bore of the testing string with the closure tool and thereby initially trapping the overbalanced hydrostatic pressure of the column of fluid in the well below the packer. Then the pressure in the well below the packer is monitored as it falls off toward the natural formation pressure. This data can be extrapolated to estimate the natural formation pressure based upon a relatively short actual test interval on the order of ten to fifteen minutes.
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Citations
22 Claims
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1. A method of testing a zone of interest in subsurface formation intersected by a well, comprising:
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(a) providing a column of fluid in said well, said column of fluid having an overbalanced hydrostatic pressure at said subsurface formation greater than a formation pressure of said subsurface formation; (b) running a testing string into said well, said testing string including a packer, a pressure monitor and a closure tool arranged to close a bore of said testing string; (c) shutting in said subsurface formation by setting said packer and closing said bore of said testing string with said closure tool and thereby initially trapping said overbalanced hydrostatic pressure of said column of fluid in said well below said packer; and (d) after step (c), monitoring a pressure fall-off in said well below said packer. - View Dependent Claims (2, 3, 4)
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5. An early evaluation method of open-hole testing while drilling, comprising:
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(a) drilling a borehole into a first subsurface formation with a drill string including a drill bit, a drill string closure valve, a packer and a pressure recording apparatus; (b) providing a column of drilling fluid in said borehole having a hydrostatic pressure at said first subsurface formation greater than a natural formation pressure of said first subsurface formation; (c) interrupting drilling of said borehole without removing said drill string from said borehole; (d) while said drilling is interrupted, shutting in said first subsurface formation by setting said packer and closing said closure valve; (e) after step (d), monitoring pressure fall-off data in said borehole below said packer for a sufficient time and with sufficient precision to extrapolate said data to said natural formation pressure, said time being less than a time required for pressure in said borehole to actually fall off to said natural formation pressure; and (f) extrapolating said data and thereby estimating said natural formation pressure. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13)
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14. An early evaluation testing string for evaluating a natural formation pressure of a subsurface formation intersecting an uncased borehole, comprising:
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a tubing string having a tubing bore;
packer means, carried by said tubing string, for sealing a well annulus between said tubing string and said uncased borehole above said subsurface formation;tubing string closure means for selectively closing said tubing bore and thereby shutting in said subsurface formation and opening said tubing bore such that said tubing bore is in communication with said well annulus; and pressure monitoring means, located below said tubing string closure means, for monitoring pressure fall-off data in said uncased borehole below said packer means with sufficient precision to allow extrapolation of said data to estimate said natural formation pressure. - View Dependent Claims (15, 16, 17)
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18. An early evaluation testing string for evaluating a natural formation pressure of a subsurface formation intersected by an uncased borehole, comprising:
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a tubing string having a tubing bore; packer means, carried by said tubing string, for sealing a well annulus between said tubing string and said uncased borehole above said subsurface formation; tubing string closure means for closing said tubing bore and thereby shutting in said subsurface formation, said tubing string closure means including a ball-type tester valve; and pressure monitoring means, located below said tubing string closure means, for monitoring pressure fall-off data in said uncased borehole below said packer means with sufficient precision to allow extrapolation of said data to estimate said natural formation pressure.
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19. An early evaluation testing string for evaluating a natural formation pressure of a subsurface formation intersected by an uncased borehole, comprising:
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a tubing string having a tubing bore; packer means, carried by said tubing string, for sealing a well annulus between said tubing string and said uncased borehole above said subsurface formation, said packer means being an inflatable packer; tubing string closure means for closing said tubing bore and thereby shutting in said subsurface formation; pressure monitoring means, located below said tubing string closure means, for monitoring pressure fall-off data in said uncased borehole below said packer means with sufficient precision to allow extrapolation of said data to estimate said natural formation pressure; a remote control system responsive to a remote command signal transmitted from a surface control station; and actuating means, operably associated with said remote control system, for closing said tubing string closure means and inflating said inflatable packer in response to said remote command signal.
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20. An early evaluation testing string for evaluating a natural formation pressure of a subsurface formation intersected by an uncased borehole, comprising:
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a tubing string having a tubing bore; packer means, carried by said tubing string, for sealing a well annulus between said tubing string and said uncased borehole above said subsurface formation; tubing string closure means for closing said tubing bore and thereby shutting in said subsurface formation; pressure monitoring means, located below said tubing string closure means, for monitoring pressure fall-off data in said uncased borehole below said packer means with sufficient precision to allow extrapolation of said data to estimate said natural formation pressure; and communication means, operably associated with said pressure monitoring means, for transmitting pressure fall-off data to a surface control station while said testing string remains in said uncased borehole.
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21. An early evaluation testing string for evaluating a natural formation pressure of a subsurface formation intersected by an uncased borehole, comprising:
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a tubing string having a tubing bore; packer means, carried by said tubing string, for sealing a well annulus between said tubing string and said uncased borehole above said subsurface formation; tubing string closure means for closing said tubing bore and thereby shutting in said subsurface formation; pressure monitoring means, located below said tubing string closure means, for monitoring pressure fall-off data in said uncased borehole below said packer means with sufficient precision to allow extrapolation of said data to estimate said natural formation pressure; and a downhole formation pump means for reducing fluid pressure in said uncased borehole adjacent said formation to a pressure below said natural formation pressure so that said pressure monitoring means can monitor a pressure buildup.
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22. An early evaluation testing string for evaluating a natural formation pressure of a subsurface formation intersected by an uncased borehole, comprising:
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a tubing string having a tubing bore; packer means, carried by said tubing string, for sealing a well annulus between said tubing string and said uncased borehole above said subsurface formation; tubing string closure means for closing said tubing bore and thereby shutting in said subsurface formation; pressure monitoring means, located below said tubing string closure means, for monitoring pressure fall-off data in said uncased borehole below said packer means with sufficient precision to allow extrapolation of said data to estimate said natural formation pressure; and position correlation means carried by said tubing string for correlating a position of said packer means relative to said subsurface formation.
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Specification