Well treatment methods and compositions

1. A method of restoring the permeability of a wellbore or underground formation wherein the permeability of the wellbore or underground formation has become impeded by sludge comprising a tar deposit or a combination of a tar deposit and a gelled synthetic polymer, the method comprising:

a) introducing an aqueous composition comprising an oxidizer, wherein the oxidizer is hydrogen peroxide or carbamide peroxide, a chelated metal activator, a surfactant selected from the group consisting of ethoxylated castor oil, ethoxylated fatty acids, alcohol sulfates, alcohol ethoxylates, amine N-oxides or a combination thereof, and a stabilizer wherein the stabilizer is urea or citric acid, into the wellbore or underground formation; and

b) contacting the sludge comprising the tar deposit or the combination of a tar deposit and a gelled synthetic polymer, with the aqueous composition for up to about 24 hours to dissolve or substantially dissolve the sludge without the formation of a precipitate, thereby restoring the permeability of the well bore or underground formation.

2. The method of claim 1 , wherein the subterranean environment comprises a geological formation.

3. The method of claim 1 , wherein the oxidizer is hydrogen peroxide.

4. The method of claim 1 , wherein the oxidizer is carbamide peroxide.

5. The method of claim 1 , wherein the oxidizer concentration in the well treatment composition is from about 500 ppm to about 25,000 ppm.

6. The method of claim 1 , wherein the chelated metal activator is selected from the group consisting of FeEDTA, FeDTPA, ferric citrate, ferrous citrate, ferrous isocitrate, ferrous aconitate, ferrous salicylate, zinc gluconate, ferrous lactate, and ferrous gluconate.

7. The method of claim 1 , wherein the aqueous composition further comprises a biocide.

8. The method of claim 1 , wherein the surfactant comprises a mixture of two or more of ethoxylated castor oil, ethoxylated fatty acids, D-limonene, alcohol sulfates, alcohol ethoxylates, or amine N-oxides.

9. The method of claim 1 , wherein the stabilizer is urea.

10. The method of claim 1 , wherein the stabilizer is citric acid.

11. The method of claim 1 , wherein the aqueous composition further comprises a co-solvent selected from the group consisting of methanol, isopropanol, and a mixture of methanol and isopropanol.

12. The method of claim 1 , wherein the sludge is deposited on the surface of the wellbore, filters, or drilling equipment.

13. The method of claim 1 , wherein the surfactant concentration in the well treatment composition is from about 0.5% to about 5%.

14. The method of claim 1 , wherein the surfactant concentration in the well treatment composition is from about 0.5% to about 1%.

15. the method of claim 1 , wherein the pH of the aqueous composition is neutral or alkaline.