Sand Washover (Well Cleanout)
Sand washover is currently the most common well intervention operation using coiled tubing. The process involves pumping cleanout fluid down the CT to loosen sand particles and flush them to the surface through the annulus between the production tubing and CT. Due to its inherent flexibility, CT not only performs routine flushing but also resolves complex downhole pipe blockages where conventional methods fail-particularly in wells where circulation cannot be established or the pipe string cannot be retrieved. CT sand cleanout enables rapid operations without well kill, ensuring high efficiency with minimal diameter constraints. This approach avoids formation damage caused by kill fluids.
Fishing Operations
Prior to CT fishing technology, traditional methods relied on wireline to retrieve "fish" (lost objects) in oil and gas wells. Downhole fish fall into two categories: (1) directly harmful objects that reduce production or increase operational difficulty/costs, and (2) items that must be retrieved for safety or mechanical reasons to resume production. Compared to wireline, CT offers three key advantages:
Axial Force Capacity: Generates greater axial force in vertical or highly deviated wells to vibrate and/or pull fish too heavy for wireline.
Circulation Capability: High-pressure circulation of fluids (e.g., nitrogen, acid) to jet, dissolve, or displace sand, mud, scale, and debris from the fish.
Operational Efficiency: Shorter cycle times and lower costs.
Fracturing
CT fracturing technology was developed to optimize perforation and fracturing processes after their initial success. While widely adopted internationally for its efficiency and cost-effectiveness, its domestic application remains limited. CT-enabled staged fracturing is now emerging, offering critical advantages: reduced well intervention time, accelerated production recovery, minimized environmental impact, and rapid ROI. Compared to conventional fracturing, CT methods save significant operational time, lower accident risks, and drastically cut costs.
Drilling
CT eliminates joint connections, maintaining stable bottomhole pressure without introducing external fluctuations. Continuous drilling fluid circulation sustains a steady-state underbalanced condition-achieving "true" underbalance-while eliminating rig dependency. Key features of CT drilling include:
Enhanced safety with fewer personnel and accidents.
Uninterrupted drilling fluid circulation.
No need for make/break operations during tripping, significantly reducing trip time while maintaining wellbore pressure control.
Simplified operations, minimal environmental footprint, and high efficiency.
Logging
CT proves instrumental in logging operations, especially in horizontal and highly deviated wells where cost and environmental constraints prevail. With its rigidity, CT can push downhole tools to any target zone for continuous logging. Circulating fluids enhance logging accuracy by eliminating cable stretch effects.
