Frac plug body

Patent metadata

Field	Value
Publication number	US-9759034-B2
Application number	US-201213452521-A
Country	US
Kind code	B2
Filing date	Apr 20, 2012
Priority date	Apr 20, 2012
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A frac plug mandrel assembly has an inner core that permits flow that is surrounded by a thin wall tube that distributes compressive loading, such as that applied by the set sealing element to the core. The core is a cylindrically shaped insert for inside the tube and allows flow until a ball or plug is landed on a seat to close off the flow through the core. The core can have a star pattern with a series of radially extending segments from a solid hub or a cylindrical shape of a honeycomb or other porous structure that has the requisite strength to resist collapse from compressive loading of the set sealing element while still allowing sufficient flow area for fluid displacement.

First claim

We claim:

1. A mandrel assembly for a frac plug for subterranean use, comprising:
a tubular mandrel comprising a wall having a longitudinal axis and an outer peripheral surface on said wall supporting a sealing element selectively radially extendable into engagement with a surrounding tubular or a borehole wall to create a compressive reaction force thereon and an inner peripheral surface on an opposite side of said wall defining a wall thickness therebetween, said inner peripheral surface extends from a first end to a second end of said mandrel defining a passage that incorporates a central axis of said mandrel to define a flow space about said central axis;
said mandrel having a seat around said passage for selective closing of said passage with an object forced to said seat with fluid pressure in a borehole extending to the subterranean location;
said passage further incorporates interconnected spaced structural members transversely spanning said passage for the substantial length of said sealing element and further spanning the central axis of said mandrel to opposed fixed contact of said inner peripheral surface such that said spaced structural members resist collapse force transmitted through said spaced structural members through said opposed fixed contact of said inner peripheral surface said structural members defining at least one fluid path through said passage between or among said structural members defined between said longitudinal axis and said inner peripheral surface.

2. The assembly of claim 1 , wherein:
said structural members comprise a cylindrically shaped core surrounded by said mandrel.

3. The assembly of claim 1 , wherein:
said structural members comprise a hub with a plurality of ribs.

4. The assembly of claim 3 , wherein:
said ribs are disposed in a plane that goes through said axis.

5. The assembly of claim 3 , wherein:
said hub is hollow.

6. The assembly of claim 3 , wherein:
said ribs have ends that contact said inner peripheral surface of said mandrel that are flat or arcuate.

7. The assembly of claim 3 , wherein:
said ribs are integrated with said inner peripheral surface of said mandrel.

8. The assembly of claim 3 , wherein:
adjacent ribs are circumferentially braced in a transverse plane to said axis.

9. The assembly of claim 3 , wherein:
said ribs have openings along their length.

10. The assembly of claim 1 , wherein:
said structural members have a honeycomb structure defining a plurality of through passages.

11. The assembly of claim 1 , wherein:
said at least one fluid path is straight through said structural members.

12. The assembly of claim 1 , wherein:
said structural members are defined by randomly shaped objects joined together to define flow passages through said passage.

13. The assembly of claim 12 , wherein:
said objects comprise spheres, rods, or mesh.

14. The assembly of claim 1 , wherein:
said structural members comprise a helix.

15. The assembly of claim 14 , wherein:
said helix is built around a core.

16. The assembly of claim 14 , wherein:
said helix is made of a plurality of flights on a constant pitch or a plurality of pitches.

17. A mandrel assembly for a frac plug for subterranean use, comprising:
a tubular mandrel comprising a wall having a longitudinal axis and an outer peripheral surface on said wall supporting a sealing element selectively extendable into engagement with a surrounding tubular or a borehole wall to create a compressive reaction force thereon and an inner peripheral surface on an opposite side of said wall, said inner peripheral surface defining a passage that is circular in cross-section to define a cylindrical space about said axis, said passage further comprising spaced structural members extending radially from said longitudinal axis to said inner peripheral surface, said structural members having a height extending the majority of the height of said sealing element while defining at least one fluid path through said passage between or among said structural members;
said structural members comprise a hub with a plurality of ribs;
said ribs define helical paths about said axis.

18. A method for completing a wellbore using at least one frac plug, comprising:
delivering at least one frac plug to a subterranean location in a formation through the wellbore, said at least one frac plug comprising
a tubular mandrel comprising a wall having a longitudinal axis and an outer peripheral surface on said wall supporting a sealing element selectively radially extendable into engagement with a surrounding tubular or a borehole wall to create a compressive reaction force thereon and an inner peripheral surface on an opposite side of said wall defining a wall thickness therebetween, said inner peripheral surface extends from a first end to a second end of said mandrel defining a passage that incorporates a central axis of said mandrel to define a flow space about said central axis;
said mandrel having a seat around said passage for selective closing of said passage including at said central axis thereof with an object forced to said seat with pressure in a borehole extending to the subterranean location;
said passage further incorporates interconnected spaced structural members transversely spanning said passage for the substantial length of said sealing element and further spanning the central axis of said mandrel to opposed fixed contact of said inner peripheral surface such that said spaced structural members resist collapse force transmitted through said spaced structural members through said opposed fixed contact of said inner peripheral surface, said structural members defining at least one fluid path through said passage between or among said structural members defined between said longitudinal axis and said inner peripheral surface;
maintaining said passage open during said delivering;
obstructing said passage with said object after said sealing element is extended to the surrounding tubular or borehole wall.

19. The method of claim 18 , comprising:
fracturing the formation;
milling out the frac plug after said fracturing.

Assignees

• King James G
• O'Malley Edward J
• Baker Hughes Inc

Inventors

• King James G
• O'Malley Edward J

Classifications

• E21B43/26

  by forming crevices or fractures · CPC title

• E21B33/1294

  characterised by a valve, e.g. a by-pass valve · CPC title

• E21B33/12 Primary

  Packers; Plugs (used for cementing E21B33/134, E21B33/16) · CPC title