Temporary well zone isolation
Disclosed herein is a temporary well isolation device, which is sealingly disposable in downhole tubing, and which has a housing with an axial passage. The temporary well isolation device also has frangible barrier element within the housing, where the frangible barrier element is sealingly engaged in the passage blocking fluid flow through the passage. The frangible barrier element bears a load from fluid pressure. The temporary well isolation device also has a disengagable constraint in contact with a frangible barrier element so as to redirect the load on the frangible barrier element from a first component of the load to a second component of the load, thereby preventing rupture of the frangible barrier element. Also disclosed herein is a method for disintegrating a frangible barrier element disposed in a passage of a temporary well isolation device.
1. A temporary well isolation device comprising:
a) a housing, sealingly disposable in downhole tubing, the housing having an axial passage therethrough wherein a first end of the passage is in fluid communication with the downhole tubing above the housing and a second end of the passage is in fluid communication with the downhole tubing below the housing;
b) a frangible barrier element within the housing, wherein said frangible barrier element is sealingly engaged in the passage blocking fluid flow through the passage so as to bear a load from fluid pressure; and
c) a disengagable constraint peripherally engaging the frangible barrier element so as to change boundary conditions from free to fixed to redirect the load on the frangible barrier element from a first component of the load to a second component of the load, thereby preventing rupture of the frangible barrier element.
2. The device of claim 1 further comprising a pump for increasing the pressure above the frangible barrier element to rupture the frangible barrier element.
3. The device of claim 1 wherein the first component of the load is the tensile component and the second component of the load is the compressive component.
4. The device of claim 1 wherein the shape of the frangible barrier element is such that the load on the frangible barrier element having the disengagable constraint in contact therewith is substantially compressive, and the load on the frangible barrier element upon the disengagable constraint being disengaged is substantially tensile.
5. The device of claim 4 wherein the frangible barrier element comprises one or more discs, said one or more discs having two sides, with at least one side being convex, and a circumferential edge.
6. The device of claim 1 wherein the disengagable constraint is annular.
7. The device of claim 6 wherein the disengagable constraint comprises an axially moveable tubular sleeve.
8. The device of claim 1 wherein the housing further comprises an axially movable tubular sleeve wherein is mounted the frangible barrier element, so that the frangible barrier element may be axially separated from the disengagable constraint.
9. The device of claim 1 further comprising a disengaging means for separating the frangible barrier element and at least a portion of the disengagable constraint.
10. The device of claim 1 wherein the frangible barrier element is composed of one or more materials, with at least one of the one or more materials being capable of withstanding a higher compressive load than a tensile load.
11. The device of claim 10 wherein at least one of the one or more materials is ceramic.
12. The device of claim 10 wherein the ratio of compressive strength to tensile strength of at least one of the one or more materials is at least 4:1.
13. A method for disintegrating a frangible barrier element disposed in a passage of a temporary well isolation device, the frangible barrier element so disposed as to block fluid flow through the passage, thereby supporting a load from fluid pressure, the method comprising utilizing the device of claim 1 .
14. The device of claim 1 further comprising a constraint removal element, wherein the disengagable constraint is at least partially removed from contact with the frangible barrier element so as to redirect the load on the frangible barrier element from a tensile component of the load to a compressive component of the load, thereby facilitating rupture of the frangible barrier element.