Shrouded core catcher

• US 4,605,075 A
• Filed: 08/31/1984
• Issued: 08/12/1986
• Est. Priority Date: 08/31/1984
• Status: Expired due to Fees

• Current Assignee: Eastman Christensen Company
• Original Assignee: Norton Christensen, Inc.
• Inventors: Radford, Steven R., Davis, J. Stanley
• Primary Examiner(s): Levy, Stuart S.
• Assistant Examiner(s): Hannon, Thomas R.
• Application Number:
  US06/646,576
• Time in Patent Office: 711 Days
• Field of Search: 175/20, 175/58, 175/226, 175/244-251, 175/253, 175/255, 175/257, 175/268, 175/309, 175/404, 166/318
• US Class Current: 175/58
• CPC Class Codes: E21B 25/02 the core receiver being insertable into, or removable from, the borehole without withdrawing the drilling pipe
• CPC Class Codes: E21B 25/04 the core receiver having a core forming cutting edge or element, e.g. punch type core barrels
• CPC Class Codes: E21B 25/10 Formed core retaining or severing means E21B25/06, E21B25/08 take precedence

Abstract

A fragmented or unconsolidated core can be cut and retained within a coring tool without substantial disturbance of the core by the use of a shrouded core catcher. A core catcher is concentrically disposed within the coring tool and outside of a smooth, cylindrical sleeve telescopically disposed inside of the core catcher. The core catcher in turn is coupled to a lower assembly which can be selectively longitudinally fixed within the coring tool, but which is otherwise temporarily coupled to the sleeve. As the sleeve is longitudinally pulled upward after the completion of the coring operation, the lower assembly becomes longitudinally fixed within the coring tool and the sleeve, which heretofore has fully covered and concealed the core catcher, begins to be withdrawn from the core catcher, leaving it unconcealed. Ultimately, the core catcher is at least partially uncovered, thereby permitting activation and contact between the core catcher and the core disposed within the coring tool. However, at all times during the coring operation, the core catcher remains concealed behind the cylindrical sleeve which extends in the coring tool throughout the substantial length of the core.

Claims

1. An improvement in the coring tool for cutting a core and including an inner tube longitudinally displaceable within said coring tool comprising:

a smooth inner cylindrical sleeve for receiving said core;

a core catcher concentrically disposed outside said sleeve and concealed from said core; and

means coupled to said sleeve and core catcher for temporarily longitudinally connecting said core catcher and said sleeve in a first configuration, and for selectively disconnecting said core catcher and said sleeve in a second configuration to allow relative longitudinal displacement of said sleeve with respect to said core catcher to unconceal said core catcher with respect to said core;

wherein said means for connecting and selectively disconnecting said core catcher and sleeve is concentrically disposed outside of said core catcher;

wherein said means for connecting and selectively disconnecting said core catcher and sleeve longitudinally restrains said core catcher within said coring tool, and then selectively disconnects said sleeve from said core catcher, thereby permitting said core catcher to become unconcealed,

whereby interfering contact between said core catcher and said core is substantially eliminated.

2. The improvement of claim 1, wherein said means for coupling and selectively decoupling said core catcher and said sleeve comprises a lower assembly, said core catcher being longitudinally fixed with respect to said lower assembly, and means coupled to said lower assembly for temporarily coupling said lower assembly to said sleeve, and then for selectively longitudinally restraining and fixing said lower assembly in said coring tool.

3. The improvement of claim 2, wherein said means for coupling and restraining comprises shear pins disposed through said lower assembly and sleeve for coupling said core catcher and sleeve, and an outer tube ring radially extending within said coring tool to provide an interference contact with said lower assembly, said outer tube ring being longitudinally fixed with respect to said coring tool.

4. An improvement in a coring tool for cutting a core comprising:

a core catcher disposed within said coring tool;

a smooth, cylindrical sleeve disposed in said coring tool and concentrically disposed inside of said core catcher, said sleeve fully covering said core catcher and providing a smooth, continuous surface of contact to said core, said sleeve being selectively displaceable with respect to said core catcher to ultimately fully uncover said core catcher; and

means for selectively activating said core catcher,

wherein said core catcher is full closure catcher, and said means for activating said core catcher comprises spring means for resiliently urging said full closure core catcher radially inward after said full closure core catcher has been uncovered by relative longitudinal displacement of said sleeve;

wherein said means for activating said core catcher being rotatably coupled to said lower assembly, said lower assembly being temporarily coupled to said inner tube and selectively detachable therefrom to allow relative longitudinal displacement between said sleeve and said lower assembly; and

wherein said means for activating said core catcher comprises an outer tube ring longitudinally fixed with respect to said coring tool, and extending radially inward to provide a longitudinal restraint to said lower assembly, said lower assembly being detached from said sleeve when selectively brought into contact with said outer tube ring, said sleeve continuing to be longitudinally displaceable within said coring tool and with respect to said full closure core catcher after longitudinal restraint of said lower assembly within said coring tool,

whereby disruptive contact between said core catcher and said core is substantially eliminated.

5. The improvement of claim 4, wherein a second core catcher is disposed within said sleeve, said second core catcher being a diametral interference fit core catcher and having an exterior frustoconical surface in contact with a mating interior frustoconical surface of said sleeve.

6. An improvement in a coring tool for cutting a core comprising:

a core catcher disposed within said coring tool;

a smooth, cylindrical sleeve disposed in said coring tool and concentrically disposed inside of said core catcher, said sleeve fully covering said core catcher and providing a smooth, continuous surface of contact to said core, said sleeve being selectively displaceable with respect to said core catcher to ultimately fully uncover said core catcher; and

means for selectively activating said core catcher,

wherein said core catcher is a diametral interference fit core catcher having an outward frustoconical shape;

wherein said means for activating said core catcher comprises a lower assembly and a collet assembly coupled to said lower assembly, said core catcher being disposed concentrically within said lower assembly, said collet assembly for temporarily longitudinally fixing said lower assembly with respect to said sleeve, longitudinally upward displacement of said inner tube activating said collet assembly to detach itself from said sleeve, thereby longitudinally restraining said lower assembly within said coring tool, and permitting said sleeve to be longitudinally displaced with respect to said lower assembly and core catcher disposed thereon,

whereby disruptive contact between said core catcher and said core is substantially eliminated.

7. An improvement in the coring tool for cutting a core and including an inner tube longitudinally displaceable within said coring tool comprising:

a smooth inner cylindrical sleeve for receiving said core;

a core catcher concentrically disposed outside said sleeve and concealed from said core; and

means coupled to said sleeve and core catcher for temporarily longitudinally coupling said core catcher and said sleeve in a first configuration, and for selectively decoupling said core catcher and said sleeve in a second configuration to allow relative longitudinal displacement of said sleeve with respect to said core catcher to unconceal said core catcher with respect to said core,

wherein said means for coupling and selectively decoupling said core catcher and sleeve is concentrically disposed outside of said core catcher;

wherein said means for coupling and selectively decoupling said core catcher and sleeve longitudinally restrains said core catcher within said coring tool, and then selectively decouples said sleeve from said core catcher, thereby permitting said core catcher to become unconcealed;

wherein said means for coupling and selectively decoupling said core catcher and said sleeve comprises a lower assembly, said core catcher being longitudinally fixed with respect to said lower assembly, and means coupled to said lower assembly for temporarily coupling said lower assembly to said sleeve, and then for selectively longitudinally restraining and fixing said lower assembly in said coring tool;

wherein said means for coupling and restraining comprises a collet assembly coupled to said lower assembly, said collet assembly resiliently and temporarily attaching to said sleeve, and an outer tube ring longitudinally fixed with respect to said coring tool, said outer tube ring radially extending within said coring tool to provide an interference contact with said collet asssembly, said outer tube ring detaching said collet assembly from said sleeve when in contact with said collet assembly,

whereby interfering contact between said core catcher and said core is substantially eliminated.