Iron contaminated acid has recently been found to promote the precipitation of asphaltenes when acidizing certain oil bearing zones. This can cause severe formation damage. Standard anti-sludging agents, normally used to prevent this, are no longer effective in the presence of iron. Commonly used iron sequesterants are found not to prevent the asphaltic sludging. Proposed mechanisms to explain these observations are presented along with a new iron control additive that does prevent the precipitaton when used with conventional anti-sludging agents. Some recommendations are made for acidizing practices when asphaltic crudes are encountered.

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