Coiled tubing (CT) deployment with hydraulic tractors in extended reach open hole horizontal wellbores has been a challenging technology in the oil industry for reasons ranging from wellbore conditions like washouts to restrictions imposed by the completions. Consequently, delivering cost-effective well interventions solutions, for example through acid treatments to enhance well performance, or production logging to understand inflow profiles in deep injector wells have been particularly demanding. The authors examine how rigorous pre-job planning and teamwork were enablers to realizing the deepest CT reach at 30,365 ft (9.26 km) measured depth (+1,336 ft longer than the height of Mount Everest at 29,029 ft) in a mega-reach open hole horizontal power injector well using a CT tractor to facilitate effective stimulation in Saudi Arabia. Among the operational challenges overcome in the well was tar accumulation on the tool string including the tractor during the well intervention. The tar accumulation on the string was part of a laterally extensive high viscosity tar layer between the overlaying oil column and aquifer. From a reservoir standpoint the tar layer posed a challenge in assuring sufficient aquifer support to the oil producers because of their partial sealing nature. The author discusses how the challenges imposed by tar restrictions and other operational concerns were overcome to ensure successful acidizing. The wells showed a marked injectivity improvement from acid stimulation thus demonstrating the benefit of informed decisions from real time fiber optic distributed temperature sensing (DTS) in fluid placement. The tractor traversed a difficult down hole environment overcoming washouts and H2S environments within the wellbore conveying the CT for an industry record tractor reach for open hole CT intervention at 30,365 ft. Concrete applications of these outcomes include the ability to employ real time information for cost-effective stimulation and real time log acquisition from extended reach open hole horizontal wells.


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