Objective The effect of mechanical properties of hydrate decomposition on reservoir stability was studied by multi-stage depressurization of gas hydrate under the action of different types of decomposition promoters.

Methods The effect evaluation and law analysis of rock mechanics stability of hydrate sediment reservoir are carried out by using multiple factors such as different effective confining pressures, different decomposition agents and their concentrations, soaking time, and through multi-level depressurization decomposition.

Results With the pressure drops and decomposition, hydrate saturation, shear strength and elastic modulus decrease gradually, and methane hydrate sediments show brittle failure.

Conclusions The higher the concentration of decomposition agent is, the greater the influence on hydrate mechanics is caused. The higher the injection concentration is, the longer the soak time is, the lower the hydrate strength is, and the more obvious the effect of the decomposition agent on reducing the hydrate strength is. Alcohol decomposition agent (ethylene glycol) is easier to weaken the strength of hydrate samples and to reduce reservoir stability than salt decomposition agent (CaCl₂) during hydrate production.