The assessment and exploitation of natural gas hydrate resources depend on the accurate identification of the distribution and thickness of the hydrate stability zone. This study develops a calculation method for determining the hydrate reservoir stability zone

grounded in the generalized phase equilibrium theory. Furthermore

the analysis software has been developed

taking into account the effects of seawater salinity

pore capillarity

and temperature offset on the hydrate stability zone. The experimental results from reservoir samples in the Qiongdongnan sea area reveal that the phase equilibrium characteristics of hydrates can be consistently characterized by a three-dimensional generalized phase equilibrium surface

encompassing temperature

pressure

and unhydrated water content. By comparing with mature software

the reliability of the proposed stability zone calculation method and software is confirmed. Stability zone calculation and analysis are subsequently performed based on the measured sample phase equilibrium curve and field conditions. The results show that

in addition to water depth

seabed temperature

geothermal gradient

and seawater salinity

the effective pore radius of sediments and temperature offset exert a significant influence on the lower boundary of the stability zone. Failure to account for the effects of pore effective radius and temperature offset results in an overestimation of the lower boundary of the stability zone by 77.4 m within this gas hydrate target area

significantly affecting the accurate assessment of resource quantity. These findings can provide theoretical support and a data reference for predicting the stability zone and accurately assessing the resource quantity of marine natural gas hydrates.