Layer-by-layer self-assembled calcium oxide microcapsules with polysaccharide films for natural gas hydrate exploitation

Abstract

As a sustainable alternative energy source, the exploitation of natural gas hydrate still faces difficulties in reaching the standard of commercial production. Traditional depressurization, thermal stimulation and increasing the contact area by using horizontal wells have limitations in field test results. A novel in-situ heat supplement method is expected to further improve gas production rate coupled with depressurization. By combining surface modification and covalent layer by layer self-assembly, a polysaccharide coated calcium oxide microcapsule as in-situ heat source in gas hydrate reservoir is proposed in this work. The heat release time was prolonged from 0.21 h to 6.82 h in simulated seawater by alternating the preparation method of calcium oxide microcapsules. The element analysis and structure properties of the polysaccharide film was characterized by scanning electron microscope with energy dispersive spectroscopy. Through particle size distribution and comparing the exothermic properties of different preparation methods, the hydration resistance mechanism of hydrophobic modification and multilayer coatings were revealed. Finally, the methane released rate stimulated by the exothermic reaction of microcapsules was delayed from 38.04 mmol/h to 8.46 mmol/h. The coupling of calcium oxide microcapsules in-situ heat supplement method and depressurization is conducive to improve the efficiency of hydrate exploitation. It explored the resource potential and addressed the challenges in natural gas hydrate exploitation.