Natural gas hydrate in deep sea exists in a certaintemperature and pressure condition. The depressurization rate during hydratedissociation by depressurization has a great impact on the gas production rateand hydrate-bearing sediment deformation characteristics. In order toinvestigate the influence of depressurization rate on temperature field

porepressure field

deformation characteristics

and gas production rate ofhydrate-bearing sediment

a group of depressurization tests with differentdepressurization rates was carried out on the apparatus independently developedby Zhejiang University that can perform linear gradient servo depressurizationfor simulating the hydrate decomposition process. The results show that thetemperature decreases first from the perimeter of the shaft where thedecomposition region starts

and then gradually spreads to the surroundingsediment at the initial stage of depressurization. Increasing thedepressurization rate appropriately can improve the production efficiency ofthe reservoir

but the higher depressurization rate may cause the hydrateregeneration

which is not conducive to gas production. Optimal gas productionefficiency can be obtained by selecting a specific depressurization rate. Inthe process of hydrate exploitation

the pore shape of the hydrate-bearingsediment can be divided into three types

according to the connection degreebetween pores and the surrounding area: completely sealed

partially sealed

and open. After hydrate exploitation

the shallow surface soil of reservoir canbe divided into three areas based on the deformation characteristics: Zone I isthe soil layer around the shaft

showing a funnel-shaped subsidence structure;the soil layer in Zone II is flat with no obvious disturbance; Zone III is theboundary soil layer

where the upward migration of water and gas production isblocked

leading to a mound like uplift zone. These deformation characteristicsare related to the migration paths and modes of gas production inhydrate-bearing sediment. Through similarity analysis

the correspondingrelationships between the decomposition time and gas production of the modeland prototype are given.