Zero-emission production of energy and methane re-using existing offshore oil and gas infrastructure

Denmark has been extracting gas and oil from the North Sea since the 1970s. However, Denmark has committed to phasing out fossil fuel production by 2050 to meet the climate goals of the Paris Agreement. The decommissioning of the offshore platforms is going to be very expensive. Therefore, considering effective repurposing of offshore platforms becomes of great interest to the oil and gas industry. In parallel to this scenario, the energy transition towards renewable and sustainable energy supply has been boosting the construction of offshore wind farms in the North Sea. Under this context, the integration of offshore wind farms with offshore oil and gas platforms could result in a better alternative to decommissioning. In this Radical Innovation Sprint project, we propose a novel zero-carbon emission energy system for both power generation and methane production. By utilizing surplus electricity generated from offshore wind farms, electrolysis can be used to split water into oxygen and hydrogen, which can be used in the Allam cycle for power generation and methanation according to the Sabatier reaction, respectively. In this novel integrated system, surplus electricity from wind farms, seawater and CO2 are converted into controllable electricity, methane and oxygen. The synthesized methane can be partly stored/exported to the existing natural gas pipeline. The portion to be stored/exported is defined as the storage ratio in this study. The integrated system has high flexibility since the Allam cycle and methanation unit can be operated separately or simultaneously. The storage ratio of the produced methane can vary between 0% and 100%. To validate the feasibility of the system, preliminary energy and mass balance are performed in Engineering Equation Solver (EES) software. 1% (45ton/day) of the total daily Danish natural gas consumption is assumed as the baseline for the modeling. Multiple scenarios with different methane storage percentages have been modeled in EES software. A sensitivity analysis is performed to identify the critical operating parameters of the novel system and the impact of the critical operating parameters on the performance of the integrated system.