Qualification of Flexible Dynamic Risers for Supercritical CO_2

摘要

In the oil and gas industry there is a growing demand for riser solutions dedicated to high partial pressures of CO_2. Part of thisrndemand is driven by deep water high pressure reservoirs with high CO_2 content. In addition there is a growing interest inrnreinjection of CO_2. The reinjection can be driven by a desire to reduce CO_2 emission as in Carbon Capture and Storage (CCS)rnprojects, but also as a way of Enhanced Oil Recovery (EOR). In all cases it is likely that CO_2 will be present at high pressuresrnand in its supercritical phase.rnNKT Flexibles is about to complete a three-year documentation and qualification program with the aim of qualifying arnbroad range of flexible pipe solutions for use with supercritical CO_2 (SCCO2). An important part of the program has beenrnmaterial qualification. For polymeric materials, the main challenge is the high solubility in some polymers of supercriticalrnCO2. This leads to potential high swelling and a risk of mechanical damage (blistering) in explosive decompression situations.rnFurthermore, supercritical CO_2 has a strong extraction power which may result in rapid loss of plasticizer in plasticizedrnpolymers.rnThe qualification program included a broad variety of tests qualifying against potential failure mechanisms. The testingrnprogram is executed on polymers in contact with the bore stream. Results show that cross-linked poly-ethylene (XLPE) innerrnliner has superior resistance to SCCO2 on all tested parameters compared to other available liner materials.rnFor steel materials, the main potential risk when exposed to supercritical CO_2 is corrosion. High CO_2 content together withrnwater forms a corrosive environment which could have some impact on the metals used. For flexible pipe application, this isrnprimarily relevant for the carcass material and end fitting which is in direct contact with the bore stream. Selection ofrnappropriate metallic materials will be based on the actual specification of the bore stream.rnThis paper will present the full scope and results of the qualification work completed for qualification of flexible dynamicrnrisers for SCCO2.