Drilling technology advances have extended the reach of well depths and complicated trajectories which have in turn created challenges for rig-less well intervention around the world. Extended reach horizontal wells up to 25,000 ft deep require that coiled tubing designs be carefully analyzed to determine when weight stacking and lock-up will prevent coiled tubing from reaching the desired total depth. If the well requires stimulation, then the benefit of coiled tubing is its enhanced placement capability to uniformly inject a treatment across a desired interval. An effective treatment diverting method can further improve these results, especially when coiled tubing is not able to access the entire pay interval. When coiled tubing locks-up before reaching the total depth for one of these treatments, a decision must be made to bullhead the treatment into the lower unreachable section, hoping for uniform placement, or to employ technology which can extend the reach. Larger diameter coiled tubing, coil tractors, liquid friction reducer, mechanical vibrational friction reduction, and buoyancy effects are techniques which can extend the reach of coiled tubing.

Sensitivity analysis was run for the aforementioned techniques and a new vibrational tool combined with a liquid friction reducer on 2-inch coiled tubing was chosen to successfully acid stimulate a horizontal open hole well. This configuration allowed the coiled tubing to reach 25 percent further than the initial lock-up point and the combination of this technique with a new viscoelastic surfactant diverting system, successfully treated the damaged well for a gain of 6,000 BOPD.

This paper will review the stimulation design process and three innovative technologies which have been combined with coiled tubing to successfully treat extended reach wells in Saudi Arabia.

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