ABSTRACT:

Solids-cleanouts using Coiled Tubing (CT) remain a major part of total activity in the CT industry. Due to the multitude of parameters that influence solids-transport, it can be very challenging to design and successfully execute solids-cleanouts with CT in highly deviated, larger wellbores with e.g. 7" production tubing, or even larger tubulars installed. Numerous papers have been written about the development of wiper trip cleanout technology and associated engineering design tools, but this paper is instead focused on important practical issues that directly impact the effective implementation of wiper trip technology in the field. This paper presents the results and lessons learned based on more than 50 solidscleanout operations conducted in the Norwegian Sector of the North Sea using "wiper trip" methodologies. Results will be presented showing how the wiper trip cleanout-methodology has improved cleanout-efficiency and success rate. Examples are presented showing how the effectiveness of cleanout-bottom hole assemblies (BHA's) involving positive displacement motors (PDMs) and mills has been improved, while simultaneously reducing stress on surface equipment during the operation. Circulation rates higher than specified maximum rates for the PDM are being used without danger of damaging the PDM while reducing the total volume pumped through the PDM during the cleanout by 80-90%. Larger outer diameter (OD) items in the BHA are kept clean of solids while wiper tripping, reducing the risk of stuck CT and protecting sensitive completion components from undesirable interactions with the PDM/mill-BHA. Multiple wiper trips can be performed in one run without the use of drop balls, while having the ability of using selected functions of critical BHA components and full-size drifting of the wellbore for subsequent operations. Field proven procedures are explained, allowing solidsloading in the annulus to be controlled and reduced when necessary, as well as estimates of solids-volumes during the cleanout to be established, based on feedback from the cleanout-BHA before any solids have actually reached surface

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