What are the best chemical options for cleaning oil field water injection lines?

[bpownall]

I was hoping some chemical engineers with experience couuld offer assistance on a question about scale/schmoo. I am working in a oil field to determine the best recipie to clean our main water injection lines which have been restricted over the years. A chemical analysis on the stuff shows that it is:

Hydrocarbons: 10%
Soluble salts: 1.40%
Calcium carbonates: .84%
Iron compounds 65.08%
Acid insolubles: 22.91%

Iron compounds were iron sulfide and iron oxide. I am getting a second test done to confirm the findings.

What are some options to clean this line? I would appreciate a variety of chemical options/procedures that I can test by flushing. My project is to focus on creating the best "recipie" to clean our lines. More options to test, the better.

Thank you for your help, I do not have much experience yet and am a first year engineer.

-Brian

 

[chemisttree]

Are your water injection lines made of steel (iron)? If so, removal of the scale could change the orifice size or even perforate the components. If the products were oxides, I would use acidic oxalic acid... don't acidify with HCl, but use straight oxalic acid. This is (or was) the active ingredient in Prestone's radiator flush years ago. Alternatively, you could use dilute phosphoric acid... the active ingredient in Naval Jelly.

 

[bpownall]

Yes the lines are made of steel. If acid was used, an acid inhibitor would be included so that it would not eat at the pipe. Why do you suggest the other types of acid? Also what is generally the cheapest acid?

Brian

 

[chemisttree]

Sulfuric is the cheapest but phosphoric is the best. I'm not sure that sulfuric acid would work quickly. Oxalic acid is probably the mildest but the most expensive.

 

[bpownall]

Sulfuric is cheaper than hydrochloric? And any reason for using a milder acid?

Thanks again

 

[chemisttree]

The reason for using milder acids is to prevent the acid from dissolving the steel lines. You should know that chloride ion catalyzes the corrosion of steel... even stainless. Use it once and kiss your lines goodbye.

 

[bpownall]

So to review, sulfuric acid is the cheapest but with my chemical analysis you do not know if it would react at all? And for this analysis, what are your personal two best options?

 

[chemisttree]

Phosphoric is the best followed by oxalic. When you eventually clean the lines, you will find that the wall thickness of the lines is now thinner. You might expect leaks.

After cleaning I would treat the lines with a dilute solution of sodium silicate (type T or N).

Corrosion Inhibition
Sodium silicate can be used as a corrosion inhibitor in potable and industrial water. Sodium silicate inhibits corrosion by forming a protective film on metal surfaces that isolates the metal from further corrosive attack. Because soluble silicates are alkaline, moreover, they bring the further benefit of increasing the pH of water. Sodium silicate can be used to inhibit corrosion of cast iron pipes, service lines, and fixtures—

http://www.pqcorp.com/common/contactus.asp?Contact_Us=ICTS" for details concerning your application.