Method for sealing an annular space in a wellbore
A method for providing one or more seals in an annular space between a well tubular and the surrounding formation or between pipes of a wellbore system includes determining an in-situ temperature, pressure, earth formation properties and one or more fluids present at one or more locations where the seals are desired. A sealing substance is placed at the locations and allowed to flow into the annular space and undergo curing to form one or more seals. The sealing substance may be a setting expoxy based, phenolic based or polyester based fluid that includes at least one solid component. The sealing substance has physical and fluid dynamic properties compatible with the determined in-situ parameters.
1. A method for providing one or more seals at a plurality of locations in an annular space between a well tubular and a surrounding formation or between pipes of a wellbore system, said method comprising the steps of
a) determining an in-situ temperature, pressure, earth formation properties and one or more fluids present at the plurality of positions to thereby determine a density of the one or more fluids present at the plurality of locations,
b) providing a sealing substance comprising an epoxy, phenolic, or polyester based fluid, at least one solid component, and a hardener for causing the sealing substance to cure,
configuring said sealing substance to have physical and fluid dynamic properties compatible with the in-situ parameters determined in step a) to thereby facilitate placing the gel at one or more of the plurality of locations where said seals are desired, and
c) injecting said sealing substance through a plurality of openings formed in said well tubular, wherein said sealing substance is configured to flow into the annular space and then around the exterior surface of the well tubular to thereby fill an entire annular space that extends between an exterior surface of the well tubular to the surrounding formation, without sinking or floating away from a point of injection, and cure to form said one or more seals at the plurality of locations to thereby isolate a first annular region of space between the well bore and the exterior surface that extends along a first longitudinal section of the well tubular from a different annular region of space between the well bore and the exterior surface that extends along a second longitudinal section of the well tubular.
2. The method according to claim 1 , wherein in said step c) said sealing substance is placed at said one or more locations using a system for injection of a substance into an annular space.
3. The method according to claim 1 , wherein the placing of said sealing substance at one or more locations are performed by an assembly inserted into said well tubular, said assembly comprising: a cutting part capable of making a hole through said well tubular, a substance chamber for storage of said sealing substance, and an injection part capable of injecting said sealing substance into said annular space.
4. The method according to claim 1 , wherein said sealing substance has thixotropic properties which are compatible with the parameters determined in step a).
5. The method according to claim 1 , wherein said sealing substance comprises silica flakes.
6. The method according to claim 1 , wherein said sealing substance comprises carbon fibres.
7. The method according to claim 1 , wherein the density of said sealing substance is in a range from about 700 kg/m3 to about 1400 kg/m3.
8. The method according to claim 1 , wherein configuring said sealing substance to have physical and fluid dynamic properties compatible with the in-situ parameters determined in step a) comprises configuring the sealing substance to have a density equal to the density of the one or more fluids determined in step a).
9. The method according to claim 1 , wherein said sealing substance comprises barite.
10. The method according to claim 1 , wherein a time for said sealing substance to undergo curing in step c) is controlled by addition of a catalyst, such as an accelerator or a retarder.
11. The method according to claim 1 , wherein said sealing substance exhibits a curing shrinkage of less than 2%.
12. The method according to claim 1 , wherein said sealing substance exhibits no curing shrinkage or expansion upon curing.
13. The method according to claim 12 , wherein said sealing substance comprises wood fibres.
14. The method according to claim 1 , wherein said sealing substance comprises a filler material for determining mechanical properties of the sealing substance after curing.
15. The method according to claim 1 , wherein in said step c) said sealing substance is placed at said one or more locations via a single hole in said well tubular or in said pipes.
16. The method according to claim 1 further comprising:
heating said one or more seals to a temperature of at least 250° C. to facilitate removal of said one or more seals.