Review on exploitation of natural gas hydrates by chemical injection method

Abstract:

Efficient exploitation of natural gas hydrates constitutes the foundation and prerequisite for their commercial utilization. As one of the vital exploitation technologies， the chemical reagent injection method facilitates hydrate dissociation by altering hydrate phase equilibrium conditions and destroying cage structures. This paper reviews the research progress of hydrate exploitation including injected alcohols， salts and hot acid solutions， and analyzes the action mechanism of various injected chemical reagents， hydrate dissociation efficiency and combined exploitation processes. The results demonstrate that alcohol-based reagents achieve thermodynamic inhibition mainly by reducing water activity via hydrophilic hydroxyl groups， yet their application suffers from severe environmental pollution and large injection dosage. Salt reagents feature low costs and environmental friendliness， while exhibiting limited exploitation potential when used alone， and combination with depressurization or thermal stimulation can boost reservoir gas production efficiency by nearly 50%. Hot acid injection enhances gas production through the synergy of chemical dissolution and heat transfer， whereas relevant mechanism research remains incomplete. Marine argillaceous silty hydrate reservoirs are characterized by high fine particle and clay contents as well as low permeability， which brings about injection obstacles for the chemical reagent injection method. The compatibility between reagent type， concentration and reservoir conditions requires urgent investigation. This study can provide references for the efficient exploitation of natural gas hydrates via chemical reagent injection.