Pipeline cleaning process

A method of cleaning the interior of a pipeline comprising:

• preparing an aqueous crosslinked gel pig by admixing (i) an aqueous liquid containing at least a trace amount of at least one divalent cation with (ii) a polymer derivative that is chemically modified by reacting at least one member selected from the group of hydroxyethyl cellulose and hydroxypropyl cellulose with a vinyl phosphonic acid in the presence of a redox system and (iii) a sufficient quantity of crosslinking activator comprising a Lewis base or a Bronsted-Lowry base to initiate crosslinking of said polymer derivative;
• introducing said aqueous crosslinked gel pig into a pipeline while crosslinking of said gel is occurring and thereafter passing said crosslinked gel pig through said pipeline at a rate sufficient to remove contaminants from the interior of said pipeline,
• reducing the pH of said crosslinked gel pig whereby the viscosity is reduced and at least a portion of said contaminants separate from said gel pig;
• and
• admixing an additional quantity of said crosslinking activator with said gel pig whereby at least a portion of said polymer derivative in said gel pig is caused to recrosslink.

A method for cleaning the interior of a pipeline utilizing a cellulose ether derivative comprising:

• preparing a pig comprising a base gel, by admixing an aqueous liquid containing at least a trace amount of at least one divalent cation with a cellulose ether derivative that is chemically modified by reacting a hydroxyalkyl cellulose with a vinyl phosphonic acid in the presence of a redox system;
• admixing a sufficient quantity of a crosslinking activator comprising a Lewis base or Bronsted-Lowry base, with said base gel to initiate crosslinking of said gel pig;
• and
• introducing said gel pig containing said crosslinking activator into a pipeline;
• passing said crosslinked gel pig through said pipeline at a rate sufficient to remove and entrain contaminants from the interior of said pipeline;
• reducing the pH of said crosslinked gel pig by the addition of a sufficient quantity of a pH reducing agent to result in a reduction in the viscosity of said crosslinked gel pig whereby at least a portion of said entrained contaminants are caused to be separated therefrom;
• and
• admixing an additional quantity of a crosslinking activator with said gel pig having at least a portion of said contaminants separated therefrom whereby said gel is cause to recrosslink.