A mature offshore field in Malaysia consists of wells that are over 20 years old and completed with dual-strings and multiple packers to produce from different sand layers. Due to the unconsolidated formation, most of the wells were completed with a gravel pack. After many years of production, the water cut has increased and fines migration has gradually plugged the gravel packs and screens. This has resulted in closing in these wells, leaving stranded potential oil behind. Continuing to produce through the plugged screens would require higher drawdown, which in turn induces greater sanding from the nearby reservoir rock and higher water cut. However, working over these wells was often noneconomical.

Initially, several wells were treated with acid but were reported to produce sand after the treatment. This was attributed to screen damage and gravel-pack failure requiring costly repair. Additionally, the acid used to remove the plugging caused by the fines migration weakened the matrix, increasing the sanding tendency.

This paper presents a case history of propellent stimulation treatment performed in two wells at this field. The gravel-packed wells were rejuvenated by applying a propellent treatment instead of acid treatments to clean the plugging in the gravel packs and screens over selected intervals that are known to be oil-bearing. Zones that could be producing water because of movement of the oil/water-contact can be left untreated so that the plugging in the screens helps in delaying water production.

Propellant has been used in the oil industry for many years, but its application has been mainly for minifracturing of consolidated rock in standard cased and perforated wells. Its application to clean gravel pack is not well known and knowledge in this domain is limited. As such, the case study started with candidate selection and proceeded through the proposed solution, conceptual job design, execution, and finally the results of the application.

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