Wiper plug with packer
A self-retaining cementing wiper plug with a packer element 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. The packer element in the wiper plug is actuated when the plug is supported by an obstruction under the plug and then compressed, the packer being maintained in compression by the holddown fingers.
1. A cementing wiper plug for sealing a wellbore having a casing, comprising:
a plurality of radially extending, elastomeric wipers extending from the cementing wiper plug further 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 movement downwardly into the casing and are sufficiently inflexible to engage the casing to prevent uphole movement of the cementing wiper plug in the casing; and
an elastomeric packer element formed at a bottom of the cementing wiper plug, the packer element being actuable between an insertion diameter and an expanded diameter so as to engage the inside of the casing and seal the wellbore against leakage of fluids from below the cementing wiper plug when the elastomeric packer element is in the expanded diameter.
2. The cementing wiper plug as described in claim 1 wherein the packer is actuable upon compression and engagement with the casing and an obstruction in the wellbore below the cementing plug, the compression being maintained by the projections when compressive force is removed.
3. The cementing wiper plug as described in claim 2 wherein the obstruction in the wellbore is a bottom cementing plug.
4. The cementing wiper plug as described in claim 1 , further comprising:
a bottom post actuable between a non-actuated, non-telescoped position and an actuated telescoped position wherein the bottom post is telescoped into a hollow core in the cementing wiper plug;
an uphole retaining shoulder formed at a bottom of the cementing wiper plug, the elastomeric element being sandwiched between the bottom post and the retaining shoulder; and
means for actuating the bottom post from the non-telescoped position to the telescoped position for compressing the elastomeric element against the uphole retaining shoulder into sealing engagement with the casing.
5. The cementing wiper plug as described in claim 4 wherein the means for actuating the bottom post are shear screws.
6. A method of sealing a casing comprising:
landing a bottom wiper plug at a bottom of a casing;
landing a top wiper plug having a packer element on the bottom wiper plug; and
applying a compressive force to the top wiper plug for actuating the packer element into sealing engagement with the casing.
7. The method of sealing a casing as described in claim 6 wherein the compressive force is a hydraulic force and is applied by pumping a fluid into the casing above the top wiper plug.
8. The method of sealing a casing as described in claim 6 wherein the top wiper plug further comprises 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 movement downwardly into the casing and are sufficiently inflexible to engage the casing to prevent uphole movement of the cementing wiper plug in the casing; and
wherein the projections act to retain compression of the packer element when the compressive force is released.
9. A method of cementing a casing into a wellbore comprising:
pumping a bottom plug to a bottom of a casing string until the plug is landed;
pumping a column of cement into the casing string;
pumping a top plug having a packer element following the cement;
applying pressure above the top plug for releasing cement through the bottom plug to be displaced into the wellbore annulus; and
actuating the packer element in the top plug to an expanded diameter for sealing against the casing and preventing cement in the annulus from re-entering the casing.
10. The method as described in claim 9 , further comprising:
permitting the cement to harden and cure; and
perforating the casing above the top plug, the packer element preventing leakage of fluids uphole past the top plug.
11. The method as described in claim 9 wherein the pressure is hydrostatic and is applied by pumping a fluid above the top plug.
12. The method as described in claim 11 wherein the fluid is displacement fluid.
13. The method as described in claim 9 wherein the packer is actuated using hydrostatic pressure.
14. The method as described in claim 13 wherein the hydrostatic pressure is created by pumping a fluid into the casing above the top packer.