Over the past several years the industry has seen significant technology advancements that have supported the new innovative applications for "Capillary Tubing Systems" from basic onshore chemical injection installations to more complex offshore applications. These innovative applications continuously challenge and redefine the boundaries of conventional well intervention methodology. Well interventions in any economically challenging environment can sometimes be difficult to justify. Capillary tubing systems have recently been deployed on challenging new projects in Asia Pacific, Europe and the USA to provide operators with an alternative cost effective method to maintain well bore integrity and enhance production.
Typical capillary tubing sizes are 1/4, 3/8, 5/8 and 3/4-inch OD. Capillary tubing systems have three primary applications and functions. The first being semi-permanent installations for the continuous injection of chemicals down hole for production enhancement. Capillary enables effective and cost-efficient delivery of production or stimulation chemicals at precise downhole depths while maintaining full ESD (emergency shutdown) and sub-surface safety valve (SCSSV) functionality. Secondly for reactivating wells that have been shut in due to the loss of SSSV control line integrity. The third being a wide range of work string activities similar to those performed by conventional "Big Coil" units such as:
- Scale Removal with Acids - Solids Removal - Gas Lifting - Cementing
- Paraffin Removal with Chemicals - Hydrate Removal - Logging Tool Deployment - Perforating
A typical capillary equipment package (Figures: 1 and 2) is comparable to but much smaller than a standard coiled tubing spread with a substantially reduced cost, environmental impact and risk exposure. The small light weight foot print is especially beneficial in conditions with crane or deck space limitations. Capillary equipment can be custom designed to suit most land or offshore applications. Capillary tubing can be installed on a semi-permanent basis or deployed as a work-string for well intervention programs. A specially designed SSSV system can enable capillary installation in wells with existing SSSV systems. Installations or well interventions can be safely performed in a matter of hours in most situations.
New and innovative capillary technologies allow the equipment to be applied to a broader spectrum of well servicing applications. This has the potential for substantial reductions in operating cost, logistical support and risk exposure that can be applied to operating environments worldwide both onshore and offshore. Wells that were once considered plug and abandon candidates due to cost, technical challenges or accessibility may now be candidates for capillary technology solutions.
Capillary technology originated in the Gulf Coast Region of the US to support production enhancement in gas well liquid loading applications. Capillary equipment deploys small-diameter (1/4, 3/8, 5/8 or 3/4-inch) tubing under live or dead well conditions. There are over 10,000 installations in North America alone. The large majority of these are for the continuous injection of chemicals to relieve gas well liquid loading problems. Capillary tubing mechanical strengths and metallurgies have rapidly developed to support the ever increasing environmental challenges encountered in down hole well conditions. Capillary tubing is now commercially available in high strength super duplex alloys that are suitable for highly deviated well bore conditions, HPHT conditions as well as high CO2 and H2S environments.
