The increasing need to improve production as well as limit the time between fracturing operations and well production in the Williston basin is a key driver in forwarding milling technology in the through-tubing environment. To keep up with advancing completion methods, through-tubing technology has been upgraded to enable an increasing number of composite plugs and ball seats to be completely milled out in one trip reducing downhole time which reduces operator costs. An operator in the Williston basin, after having set 79 composite plugs in two separate wellbores and completed fracing operations in the Bakken shale, was prepared to bring wells online. The removal of 79 plugs in two wellbores normally takes a significant amount of time, and involves several trips downhole and pulling the bottomhole assembly (BHA) to change out worn components. Utilizing a milling-specific application for removing composite plugs, 43 composite plugs in the first well were removed in a single run using a workover rig. The same mill that was used with the first well was sent back to the shop and inspected and used on the second well to remove 36 composite plugs from the second wellbore without redress. Milling a large number of composite plugs in two wells in one trip equalls time saved and significantly reduced cost. The paper describes the operation, the downhole components of the BHA, including the application-specific milling technology, and the cost savings to the customer during the record-setting mill out operation.

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