Multi-stage treatment for iron sulfide scales
Multi-stage treatment methods for the treatment or removal of iron sulfide scales in subterranean operations and operations involving the production and/or transportation of oil and gas. In one embodiment, the methods include identifying one or more types of iron sulfide scale present in a portion of a subterranean formation; introducing a first treatment composition comprising an acid into at least a portion of the subterranean formation to partially dissolve the iron sulfide scale therein; and introducing a second treatment composition into the portion of the subterranean formation after the first treatment composition, the second treatment composition comprising an iron sulfide treating additive selected based at least in part on a type of iron sulfide scale identified in the subterranean formation.
1. A multi-stage treatment method comprising:
identifying one or more types of iron sulfide scale present in a portion of a subterranean formation;
introducing a first treatment composition comprising an acid into at least a portion of the subterranean formation to partially dissolve the iron sulfide scale therein; and
introducing a second treatment composition into the portion of the subterranean formation after the first treatment composition, the second treatment composition comprising an iron sulfide treating additive selected based at least in part on a type of iron sulfide scale identified in the subterranean formation.
2. The method of claim 1 wherein at least a portion of the iron sulfide scale remains in a portion of the subterranean formation when the second treatment composition is introduced, and the method further comprises allowing the second treatment composition to at least partially dissolve the remaining portion of the iron sulfide scale.
3. The method of claim 1 further comprising introducing one or more spacer fluids into at least a portion of the subterranean formation after the first treatment composition and before the second treatment composition.
4. The method of claim 1 wherein identifying one or more types of iron sulfide scale present in a portion of the subterranean formation comprises retrieving a sample of iron sulfide scale from a portion of the subterranean formation.
5. The method of claim 1 wherein the iron sulfide treating additive comprises at least one additive selected from the group consisting of: a chelator; a reducing agent; acrolein; a weak acid; and any combination thereof.
6. The method of claim 5 wherein the chelator comprises at least one compound selected from the group consisting of: trishydroxymethylphosphine (THP); tetrakis(hydroxymethyl)phosphonium sulfate (THPS); ethylenediaminetetraacetic acid (EDTA); and any combination thereof.
7. The method of claim 1 wherein the first treatment composition further comprises a hydrogen sulfide scavenger.
8. The method of claim 1 wherein the first treatment composition further comprises a corrosion inhibitor.
9. The method of claim 1 wherein the first treatment composition further comprises a hydrogen sulfide scavenger and a corrosion inhibitor.
10. The method of claim 1 wherein the acid comprises at least one organic acid.
11. The method of claim 1 wherein at least one of the first and second treatment compositions are introduced into the portion of the subterranean formation using one or more hydraulic pumps.
12. A multi-stage treatment method comprising:
identifying one or more types of iron sulfide scale present in a portion of a conduit or container;
introducing a first treatment composition comprising an acid into at least a portion of the conduit or container to partially dissolve the iron sulfide scale therein; and
introducing a second treatment composition into the portion of the conduit or container after the first treatment composition, the second treatment composition comprising an iron sulfide treating additive selected based at least in part on a type of iron sulfide scale identified in the conduit or container.
13. The method of claim 12 wherein the conduit or container comprises a pipeline for transporting hydrocarbons from one location to another.
14. The method of claim 12 wherein identifying one or more types of iron sulfide scale present in a portion of the conduit or container comprises retrieving a sample of iron sulfide scale from a portion of the conduit or container.
15. The method of claim 12 wherein the acid comprises at least one organic acid.
16. The method of claim 12 wherein the iron sulfide treating additive comprises at least one additive selected from the group consisting of: a chelator; a reducing agent; acrolein; a weak acid; and any combination thereof.
17. The method of claim 12 wherein the first treatment composition further comprises a hydrogen sulfide scavenger and a corrosion inhibitor.
18. A multi-stage treatment method comprising:
retrieving a sample of iron sulfide scale from a portion of a subterranean formation;
identifying one or more types of iron sulfide scale present in the sample;
introducing a first treatment composition comprising an acid into at least a portion of the subterranean formation to partially dissolve the iron sulfide scale therein, wherein at least a portion of the iron sulfide scale remains in a portion of the subterranean formation; and
introducing a second treatment composition into the portion of the subterranean formation after the first treatment composition to at least partially dissolve the remaining portion of the iron sulfide scale, the second treatment composition comprising an iron sulfide treating additive selected based at least in part on a type of iron sulfide scale identified in the sample.
19. The method of claim 18 wherein the acid comprises at least one organic acid.
20. The method of claim 18 wherein the iron sulfide treating additive comprises at least one additive selected from the group consisting of: a chelator; a reducing agent; acrolein; a weak acid; and any combination thereof.