In the recent years horizontal well technology evolved in the Middle East field development strategies becomes favored over vertical and deviated wells offering the advantage of maximized reservoir contact, higher production rates and better access to reserves. However, most of these horizontal wells are completed openhole with little alternatives for stimulation, water shutoff or workover treatments. A very challenging task to stimulate long openhole sections effectively due to poor acid distribution especially in reservoirs with high permeability streaks that require effective diversion techniques. The efficiency of chemical diverting agents in terms of flow distribution and uniform coverage is limited when it comes to treat such complex wells with long openhole intervals (see Fig. 1).

This paper illustrates a case history where an innovative technique was used on stimulating a naturally completed horizontal well that experienced a production drop to zero shortly after the completion in 2004 due to formation damage and incomplete cleanup. This technique combined mechanical and chemical diversion, using selective openhole completion allowing the wellbore mechanical segmentation into six small intervals based on petrophysical and reservoir evaluation, so that the selected sections can individually be stimulated evenly and inflow contribution from the entire openhole section can be maximized win one continuous operation.

The treatment used the advanced emulsified acid technology to achieve deep penetration and better etched fracture conductivity. Viscoelastic surfactant self-diverting Acid (VES diverting acid) was used as the chemical diverter to assure good zonal coverage across each stimulation stage. Greatly increasing the effectiveness of the treatments the combination of technologies allowed successful stimulation of the well with 20:1 permeability contrast. The last stabilized measurement indicates sustained natural production of 10,000 bopd, which is five times the field average and three times greater than the best well in the field without requiring artificial lift.

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