Repeatedly Increased Efficiency and Success Rate From a New Solids-Cleanout Process Using Coiled Tubing: A Review of Recent Achievements From More Than 100 Operations

Abstract

Summary Solids cleanouts using coiled tubing (CT) remain a major part of total activity in the CT industry. Because of the multitude of parameters that influence solids transport, it can be very challenging to design and execute solids cleanouts successfully with CT in highly deviated, larger wellbores with 7-in. 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 focused instead 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 a database that was compiled from more than 100 solids cleanout operations 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 (BHAs) 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 to use selected functions of critical BHA components and full-size drifting of the wellbore for subsequent operations. Field-proven procedures are explained, allowing solids loading in the annulus to be controlled and reduced when necessary, and allowing estimates of solids volumes during the cleanout to be established, on the basis of feedback from the cleanout BHA before any solids have actually reached surface.