The Journey of CO2 from the Capture to the Subsea Sequestration

Abstract Carbon capture and storage is among a few technologies with the potential to enable significant CO2 emission reductions from hard-to-decarbonize sectors such as offshore production facilities. Within this context, many offshore operators are evaluating measures to reduce Greenhouse Gas (GHG) emissions from their operations including those in Deepwater, and Energy contractors are re-shaping their technological expertise and potential solutions for meeting such challenging and increasing demand for lowering operations emissions. The present paper will focus on a specific potential application, related to the offshore pipeline CO2 transportation from an offshore capture facility (deepwater or shallow water), to a permanent subsea storage location. The work presented is the outcome of a joint effort by Exxon Mobil and Saipem articulated through phases: A framing exercise to shape different scenarios to be analyzed. Engineering execution feasibility screening to characterize the above-mentioned scenarios, and to determine: What are the hurdles for deepwater CO2 capture, transportation via offshore pipeline and its sequestration? The challenges associated with CO2 transportation via an offshore pipeline, are spread among all the areas characterizing the system, e.g.: Flow Assurance: the flowing conditions of CO2 are strongly affected by the impurities content, and the bathymetry which the pipeline path traverses. Material Selection: potential corrosion damage mechanisms must be carefully addressed vs. operating and transient flowing conditions. Structural Integrity: the risk of failure associated with potential Running Ductile Fracture (RDF) must be considered and managed since early design phases. Subsea Equipment: the equipment, not limited to the pipeline and riser, shall be assessed in terms of readiness and technological gaps, if any. Safety: the potential risk of subsea CO2 dispersion shall be carefully evaluated. Economics and Supportive Government Policy: Costs are generally key challenges associated with these potential emissions-reduction initiatives. The study performed covered all the above areas through the involvement of Companies Engineering Departments, SME and Developers. All main building blocks of an offshore CO2 transport system have been analyzed during a high-level conceptual design activity to explore any potential criticality vs. their deployment in the specific application. Location/asset-specific factors, supportive government policy, and continued technological advancements can be expected to remain important elements in operator analyses of the commercial viability of potential emissions reduction initiatives. The findings from the presented activity provide offshore Operators considerations for the possibility of transporting CO2 between offshore CO2 capture location to sequestration reservoirs for permanent storage and provide the offshore industry with useful points of reflection.