SCCO2 Flushing Technology: The Supercritical Revolution

Abstract

Abstract Objectives Research indicate that 80% of all failures in fluid transfer systems are caused by contamination. Contamination causes huge gaps in both safety and reliability and shortening the lifespan of, systems. Subsea systems are often controlled by very long umbilical's/control-lines (>6 km) with no efficient cleaning option. It is necessary to clean these lines with turbulent flow, which can be difficult to obtain with conventional cleaning fluids Method With the Super Critical CO2 (SCCO2) technology, it is now possible to clean very long narrow pipes with turbulent flow, not possible with conventional flushing methods. Due to the very low viscosity, diffusivity, and no surface tension of the CO2, it possible to reach a level of cleanness never seen before. Using the pressure & temperature it is possible to manipulate the density needed to carry the particles. When the particles are carried out of the system, the liquid CO2 is converted into gas in the separator, and the contamination suspended in the CO2 drops out. Results This technology has been proven on a proof of concept test (onshore) with two 3rd party participance, flushing a 6,5km ¼" dual control-line. This line was cleaned with laminar flow (Reynolds No. under 3000) and had a certificate that said it was cleaned to NAS1638 grade 6. It was proved, using SCCO2 with a Reynolds No. of 42.000, that the line was not clean, [and was NAS1638 grade 12]. It was then cleaned to NAS1638 grade 3, best we have ever seen. Also, the SCCO2 technology was proved offshore, by cleaning a 38km ½"ID Umbilical for Wintershall Noordzee, from NAS1638 grade 12 to Grade 3 with a Reynolds No. of over 30.000. This umbilical had the same issue as in the proof of concept test. The line was claimed to be clean, but the operator experienced that the chemical injection line was blocked by contamination. This caused a lot of shutdowns and was very costly. After the umbilical was cleaned with the SCCO2 technology, the operator has not had any shutdowns due to contamination or blockages for over 9 months now. Novelty With the SCCO2 technology, it is possible to clean or unblock very long tubes/lines, to a cleanness never seen before. The cleanliness and unblocking possibilities are a result of the unique characteristics of the CO2, and the high Reynolds No. possible by using CO2. This opens more possibilities that previously was not possible and lacking in the industry. It will make the systems more safe, reliable and reduce cost and increase the production up-time.