Seasonal CO2 Storage in Q16-Maas, The Netherlands

Greenhouses in The Netherlands use elevated CO2 levels to enhance crop growth. Currently, they obtain most of their CO2 through combustion of natural gas in combined heat and power installations. An increasing number of greenhouses is moving away from natural gas, switching to geothermal energy as a heat source and using CO2 from industrial sources. Supporting this transition to sustainable energy for greenhouses would require an increase in and secure supply of external CO2. This could be achieved via seasonal buffering of CO2 in a sandstone reservoir to match supply and demand, and provide security of supply during periods of maintenance at the industrial supply sites. This paper explores the potential of the depleted gas and condensate field Q16-Maas as a seasonal CO2 buffer, by estimating the maximum feasible injection and production rates and cumulative seasonal buffered volumes. With a CO2 storage capacity of about 2 Mt, the gas field would require two 6-months injection periods, before commencing regular production – injection cycles. Both injection and production of CO2 occur at a rate of 20 kg/s. This would lead to an additional CO2 supply to the greenhouses of 315 ktonne in summertime, increasing current offtake by about 60%, leading to a correspondingly decreasing use of natural gas. The back-produced CO2 will be contaminated with hydrocarbons, primarily CH4, with a concentration as high as 20% in the first injection cycle, decreasing with each consecutive cycle. The hydrocarbons can however easily be separated from the CO2 by the use of a condenser and flash separator. The primary constraint on the buffer potential comes from the back-production conditions in the production well. Well dynamics simulations show that the pressure and temperature decrease of the CO2 during its ascend from bottom hole to wellhead is higher when the production volume increases. The conditions of the CO2 during production should remain above both two-phase and hydrate formation conditions. Optimal conditions within the reservoir and well constraints are obtained when the bottom-hole CO2 temperature is at the reservoir value of 105 °C. This requires significant compression during injection to wellhead conditions of 80 °C and 147-159 bar, but maximises the back-production rate at 20 kg/s. Rough cost estimates for the wellhead facilities and separation technologies show that seasonal buffering could be economically attractive.