As a result of the continuous development of drilling technology, more complex wells can be drilled to overcome reservoir challenges and reach target intervals. Over the last decade, innovative drilling techniques have enabled a significant increase in the number of multilaterals and extended-reach wells; this imposes new challenges regarding well accessibility for rigless intervention techniques, which has driven operators, manufacturing, and service companies to develop innovative strategies for servicing these fields.

In Saudi Arabia, one extended-reach power water injector (PWI) well was sidetracked to enhance injectivity. During the sidetrack, it was necessary to drill more than 1,000-psi overbalance due to the presence of high-pressure zones across the horizontal section, which resulted in formation damage on the low-pressure intervals. Based on this situation, a well intervention plan was considered which would use Coiled Tubing (CT) acid stimulation to remove the formation damage especially toward the end of the open-hole horizontal section.

This operation involved two particular challenges; the first of which was the CT reach across the open-hole section, especially when CT forces simulation predicted a maximum coverage of 50% of the target zone. The second challenge was implementing the proper jetting tool to be able to function with the combination of the downhole tractor and high rate acid stimulation to ensure penetration across the filter cake and remove formation damage in the entire target zone. In order to make this solution feasible a specially designed downhole tractor was engineered, manufactured and incorporated with a newly designed high pressure jetting tool to be able to have full functionality of the downhole tractor while still performing full high rate stimulation to penetrate the damaged zones.

This paper describes the combination of slim tractor and high-pressure jetting tool to conduct an effective acid stimulation job in an extended-reach PWI and have a CT reach of 98% instead of the predicted 50% reach in one of the major carbonate reservoirs in the Saudi Arabia. In addition, this paper provides design methodologies, best practices and industry lessons learnt from the experiences gained in the implementation of multi-purpose tool solution in Saudi Arabia.

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