Thermochemical Heat Storage Biogel with Environmental Friendliness for Solar-Powered Heavy Oil Recovery and Carbon Capture

Solar thermal enhanced oil recovery (Solar TEOR) methods with energy-saving and eco-friendly nature have attracted growing research interest. However, due to sunshine duration and weather change, the solar heat supply from concentrating sunlight features intermittency and instability, causing an energy efficiency decline of heavy oil thermal recovery. Meanwhile, huge carbon emissions from the oil production industry aggravate the greenhouse effect. In this work, a thermochemical heat storage biogel WS/SA/G@MgCO3, affording good carbon capture performance, was designed and synthesized through a one-pot reaction for heavy oil cleaner production, wherein the agricultural residue─wheat straw powder─was applied as the matrix, with MgCO3 serving as the heat retainer and graphite acting as the thermal conduction enhancer. Based on experimental results, the thermal degradation/recarbonation reaction of MgCO3 in biogel offered a high heat reservoir capacity, energy storage density and CO2 adsorption volume, respectively, up to 0.81 kJ·g–1, 0.72 kJ·g–1, and 1.1 g·g–1. However, the graphite thermal transfer channel endowed the biogel with large heat transfer velocity, heat input/output efficiency, and CO2 capture speed reaching 2.03 W·m–1·K–1, 11.8 kW·kg–1/2.7 kW·kg–1, and 0.101 g·g–1·min–1, respectively. Moreover, the gel-assisted oil recovery mode, solar powered steam flooding in daytime + WS/SA/G@MgCO3 biogel-heated CO2 flooding at nighttime, contributed to a 24/7 heavy oil thermal production, elevating the energy utilization, oil recovery rate, and CO2 storage (55 mg·mL–1) in the formation, with energy consumption (per unit oil recovery) and energy/exergy efficiency reaching 57 J·(mL oil)−1 and 45.7%/13.6%, respectively. On the other hand, WS/SA/G@MgCO3 gel from wood biomass was readily biodegradable and bioavailable, in favor of underground ecology protection during oil recovery. This work proposes a green power-energized heavy oil production scheme and a CCUS (carbon capture, utilization, and storage) strategy for the upstream industry.