Description: In just a few short years, the oil and gas industry has seen the application of capillary tubing technologies grow from a relatively simple onshore use in the US to complex and innovative uses in intervention and permanent installations across the globe both onshore and offshore.
Application: The latest advancements in capillary technology have opened up a whole new market for well intervention. Wells that were once deemed as P&A candidates, due to cost or technical challenges, are now economically viable producers. Wells and platforms inaccessible to traditional coiled tubing units, due to limited work decks and de-rated cranes, are now candidates for well intervention.
Results, Observations, Conclusions: For the past decade, capillary strings have been used as a method for continual down hole injection of production chemicals to treat for a wide array of production problems. Recent innovations and advancements have expanded the market and uses of capillary. Thru-tubing capillary installations are now possible in wells with SCSSV's (Surface Controlled Sub-Surface Safety Valves). This breakthrough is especially important for offshore liquid loading wells that were not completed with any form of artificial lift. Capillary technologies have made it possible to regain surface control of SCSSV's with failed control lines, through tubing without a work over. The chemical injection point in subsea wells can now be extended to the end of the sand screen to eliminate mineral and organic deposition problems. A through-tubing solution for lowering the lowest point of gas lift to the bottom of the well is possible with larger capillary strings. Jobs that only require small amounts of chemical such as the remediation of hydrate plugs, salt plugs, and small amounts of scale and paraffin are now possible with a small capillary unit.
Significance of Subject Matter: The premature P&A of liquid loaded and remote wells around the world leave significant amounts of unrecovered hydrocarbons behind. This problem can be partially resolved by informing operators of the alternative, cost-effective options that are available. Chemical spotting through capillary and through-tubing capillary installations for artificial lift allow these operators to recover significantly more reserves.
Over the last decade, capillary strings have become an accepted and well used method for continuously injecting production chemicals to the bottom of a well. This technology, which found its start in the Gulf Coast region of the US, has rapidly spread across the US and is starting to find its way into many other parts of the world. As different reservoirs, wellbore conditions, completions, surface equipment, and well locations are encountered, the capillary technology has found new, innovative uses and applications outside of its original intended use.
In the upstream oil and gas industry, a capillary string is defined as continuous stainless steel tubing with an OD of less than 1 inch. Typical sizes for capillary tubing are Â¼", 3/8", 5/8" and Â¾". The typical metallurgies encountered are 2205 duplex, 2507 super duplex, Inconel 825, and Inconel 625. A capillary tubing unit enables "live well?? deployment of a capillary string into a well. Capillary tubing units operate similar to conventional coiled tubing units but at a much smaller scale. On land wells with no SSVs or SCSSVs, the capillary string is hung off on top of the wellhead with a packoff being used for well control and a set of bi-directional slips used to suspend the weight of the tubing.
Thanks for the feed back gents.
I'm looking for small bore CT to possibly be used for N2 or chemical injection. Terry do you have any info on the chemical injection application?