Method and apparatus for taking an undisturbed core sample
First Claim
1. A formation core sampling apparatus for a subterranean well where fluids are found, comprising:
- a housing;
core barrel means selectively movable with respect to said housing by fluid pressure, from a retracted position to facilitate placement of an end of said housing into the formation to an extended position for obtaining a formation specimen in said core barrel;
sealing means releasably mounted to said core barrel means for isolating the fluids in the well from said core barrel means as said core barrel means is selectively moved into the formation, in its movement from said retracted to said extended position.
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Accused Products
Abstract
The invention is a coring device which has features to seal off from the well fluids prior to taking of the specimen. The apparatus can be hydraulically or pneumatically actuated to move an inner string which is connected to a core barrel. Prior to moving the core barrel, an outer tube is sealingly pushed into the formation. Once the outer tube has been set into the formation, the inner tube drives the core barrel into the formation, leaving behind a rabbit. A clam shell is located at the forward end which stays open as the core barrel is driven into the formation and closes as the core barrel is withdrawn into the outer tube to retain the core. The pneumatic or hydraulic pressure continues to be applied to the inner string as the core barrel is withdrawn into the outer tube. Upon full retraction of the core barrel into the outer tube, a ball valve is actuated to seal off the core barrel. At that time, the hydraulic or pneumatic pressure is removed and the apparatus is pulled to the surface. The core barrel has a venting feature to allow any gas in the core barrel to escape as the core barrel fills with the core sample.
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Citations
19 Claims
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1. A formation core sampling apparatus for a subterranean well where fluids are found, comprising:
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a housing; core barrel means selectively movable with respect to said housing by fluid pressure, from a retracted position to facilitate placement of an end of said housing into the formation to an extended position for obtaining a formation specimen in said core barrel; sealing means releasably mounted to said core barrel means for isolating the fluids in the well from said core barrel means as said core barrel means is selectively moved into the formation, in its movement from said retracted to said extended position. - View Dependent Claims (2)
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3. A formation core sampling apparatus for a subterranean well where fluids are found, comprising:
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a housing; core barrel means selectively affixed to said housing and selectively movable with respect to said housing from a retracted position to facilitate placement of an end of said housing into the formation to an extended position for obtaining a formation specimen in said core barrel; plug means selectively affixed to said core barrel means at an end thereof for isolating the fluids in the well from said core barrel means as said core barrel means is selectively moved into the formation, in its movement from said retracted to said extended position; a seal between said plug means and said core barrel means; piston means connected to said core barrel means to move said core barrel means selectively into the formation; first retaining means on said piston means to retain said piston means stationary until said first retaining means are overcome; and an annular space between said housing and said core barrel comprising opposed bearing surfaces on said housing; wherein said housing, core barrel means, and said plug means can be moved into the formation in tandem a sufficient depth to isolate said core barrel means from the well fluids; and wherein application of fluid pressure to said piston means creates a net force in said annulus and said net force acts on said housing in a direction toward the formation prior to defeat of said first retaining means. - View Dependent Claims (4, 5, 6, 7, 8, 9)
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10. A core sampling tool comprising:
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a housing; a core barrel releasably mounted to said housing for movement through an entrance thereon between an extended position for sampling and a retracted position; releasable retention means to selectively hold said core barrel to said housing to facilitate their tandem insertion into a formation to a depth sufficient to exclude well fluids from the core barrel as it is subsequently moved to its extended position; releasable barrier means to selectively block off said entrance to said core barrel as said housing, core barrel and barrier means are pushed into the formation in tandem prior to movement of said core barrel to its extended position. - View Dependent Claims (11, 12)
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13. A core sampling tool comprising:
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a housing; a core barrel mounted to said housing for movement through an entrance thereon between an extended position for sampling and a retracted position; retention means to selectively hold said core barrel to said housing to facilitate their tandem insertion into a formation to a depth sufficient to exclude well fluids from the core barrel as it is subsequently moved to its extended position; barrier means to selectively block off said entrance to said core barrel as said housing, core barrel and barrier means are pushed into the formation in tandem prior to movement of said core barrel to its extended position; and biasing means acting on said housing to apply a net force on said housing tending to keep it in the formation as said core barrel moves from its retracted to its extended position; wherein said barrier means is a plug sealingly mounted to the inside of said core barrel adjacent its entrance and having a tapered profile at its leading end which extends beyond said core barrel entrance, said housing and core barrel also having a tapered profile adjacent said tapered profile of said plug to facilitate their embedment into a formation; and wherein said biasing means further comprises; a piston connected to said core barrel; a flowpath from the end of said core barrel opposite said plug to said piston; an annular space between said housing and said core barrel, said flowpath extending into said annular space; said annular space having a pair of opposed bearing surfaces of unequal cross-sectional area; whereupon application of fluid pressure in said passage against said piston, a net force is applied to said housing due to pressure in said annular space acting on said bearing surfaces which tends to push said housing into the formation. - View Dependent Claims (14, 15, 16)
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17. A method of obtaining core specimens from a formation, comprising the steps of:
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lowering a tool having a housing and a core barrel with its entrance initially plugged off to a point adjacent the formation; retaining the core barrel to the housing; driving the assembly of the core barrel, housing, and plug at the entrance to said core barrel into the formation to a sufficient depth to isolate the plugged of entrance to the core barrel from well fluids; moving the core barrel with respect to said housing and with respect to said plug at its entrance to obtain a sample; and applying a downward force on said housing as said core barrel is moved with respect to said housing and said plug to help retain said housing in the formation a sufficient depth to isolate the core barrel from well fluids. - View Dependent Claims (18, 19)
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Specification