Offshore production of some crude oil wells is greatly affected by the formation of wax which can be a cause great economical loss in oil recovery. Heat transfer from oil production pipeline to the relatively low temperature seawater at the seabed leads to the oil cooling down to temperatures below the Wax Appearance Temperature (WAT or Cloud Point).
The ‘coldflow’ concept looks to remediate wax accumulation by mechanical means rather than the existing more expensive chemical or direct heat treatment methods. A test loop has been designed and built to simulate a ‘coldflow’ production system incorporating the following features and requirements:
Dewaxing Pigs pre-installed in a automatic launcher.
The pigs are designed to negotiate running through the loop, passing through all pipe loop features such as valves, check valve and flow diverters while effectively scraping wax from the pipe ID as it forms.
The pig seal material and geometry has been selected to minimise wear and maximise lifespan for each pig. The intention being that each pig is capable of as many circuits of the coldflow pipe loop as practically possible.
"We can state that the wax cleaning pig has been working well, and that this product is robust and without any failure identified"
Subsea 7 AS