Self-anchoring cementing wiper plug
A self-retaining cementing wiper plug has two or more steel or carbide tipped holddown fingers or slips extending radially outward from the plug for engaging the inner surface of the casing and preventing the plug from moving uphole over time and potentially interfering with other downhole apparatus such as a pump.
1. A self-anchoring cementing wiper plug having a plurality of radially extending, elastomeric wipers extending therefrom for insertion into a casing and for wiping engagement with an inner wall therein, the improvement comprising:
one or more substantially inflexible projections biased radially outward from the cementing wiper plug and angled uphole,
wherein, the one or more projections are moveable inwardly sufficiently so as to permit downhole movement into and along the production casing and are sufficiently inflexible for gripping engagement with the inner wall of the casing to prevent uphole movement of the plug therein.
2. The cementing plug as described in claim 1 further comprising two or more substantially inflexible, circumferentially spaced projections and wherein the two or more substantially inflexible projections are individual holddown fingers.
3. The cementing plug as described in claim 2 wherein the two or more holddown fingers are embedded at a first end in an elastomeric covering and extend outward therefrom to contact the casing at a second end.
4. The cementing plug as described in claim 3 wherein the two or more holddown fingers are positioned in a space formed between two adjacent wipers.
5. The cementing plug as described in claim 3 wherein the two or more holddown fingers are embedded in the elastomeric wipers.
6. The cementing plug as described in claim 3 wherein the holddown fingers are constructed of spring steel.
7. The cementing plug as described in claim 3 wherein the second ends of the holddown fingers are carbide tipped.
8. The cementing plug as described in claim 3 further comprising an anchor formed at the first end of the finger for anchoring the finger in the elastomeric covering.
9. The cementing plug as described in claim 3 further comprising a ring from which the holddown fingers extend.
10. The cementing plug as described in claim 9 further comprising an anchor formed about an inner edge of the ring for securing the ring in the elastomeric covering.
11. The cementing plug as described in claim 3 comprising two holddown fingers circumferentially spaced 180 degrees relative to each other, about the plug.
12. The cementing plug as described in claim 3 further comprising a plurality of holddown fingers spaced circumferentially about the plug.
13. The cementing wiper plug as described in claim 1 wherein the substantially inflexible projections are slips.
14. The cementing wiper plug as described in claim 13 wherein the slips are biased outwardly for engaging the casing.
15. The cementing wiper plug as described in claim 14 wherein the slips are biased outwardly by an elastomeric covering.
16. The cementing plug as described in claim 13 wherein the slips are shearable from a non engaging position to a casing engaging position.
17. A cementing wiper plug having a plurality of radially extending, elastomeric angled wipers for wiping an inside surface of casing, the improvement comprising:
one or more slips biased radially outward from the cementing plug for engaging the casing and preventing uphole movement of the plug,
wherein, the slips are moveable from a first casing non-engaging position to a second casing engaging position.
18. The cementing plug as described in claim 17 further comprising:
an inflexible core having an upper portion and a lower portion, the lower portion having a recess for receiving the upper portion;
a unitary elastomeric covering enclosing the upper and lower portions from which the wipers extend and having a plurality of ports spaced circumferentially thereabout and proximate a lower end of the upper portion;
a plurality of slips, each slip being shearably connected between the upper and lower core and stowed in the ports in the elastomeric covering in the casing non-engaging position
wherein, when the connection between the slips and the core is sheared, the top core is displaced downward into the recess in the bottom core and the slips are forced outwards into engagement with the casing.
19. The cementing wiper plug as described in claim 18 wherein the shearable connection is a plurality of shear tabs connected between the upper core and the lower core.