It’s a fact of life – many gravel packs plug up. As time passes, skin factors go up and production rates go down. Much of the money that was spent on creating a sand control completion with minimum skin may eventually count for nothing. In order to prolong the effectiveness of the gravel pack (GP) and as a added benefit reduce the need for workovers, a method was developed in the Far East to remove these fines and dramatically reduce the skin factor. The method employs relatively small volumes of a specialized HF (hydrogen fluoride) acid system, designed to penetrate into the GP and very near wellbore area. The HF acid system uses an organo-phosphonate (HV) acid to control the production of HF and to control and drastically reduce potentially damaging secondary and tertiary precipitates. The system will be referred to as HV:HF Acid in this paper.

This HV:HF Acid system can be applied to any well with a screen and/or GP that has damage caused by the migration of formation fines and/or drilling mud particles. It is not limited by the type of screen or gravel nor by the length or number of sets of screens. The method has potentially enormous implications throughout the world. Any well with a GP or screen could potentially benefit from this method of treatment, including long horizontal intervals, which up to now have been very expensive to treat, due to the larger volumes of acid normally recommended.

The results of this HV:HF Acid method will be illustrated by 3 case histories from the Far East, including horizontal wells. The observations from these treatments allow us to conclude that this method is highly successful, cost effective, and applicable to a broad spectrum of well conditions. The reduced stimulation volumes provide better economics, so that even long sections and horizontal wells can now be stimulated at reasonable costs.

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