Distinct gas production characteristics from laboratory-synthesized Class I, II, and III hydrate reservoirs: A novel thermally-segmented rotatable approach

• Designed a novel 360° rotatable reactor with segmented temperature control. • Synthesized Class I-III natural gas hydrate reservoirs in the laboratory. • Analyzed the production characteristics of Class I-III reservoirs. • Studied the effects of key parameters on Class I reservoirs. • Proposed depressurization mechanisms for Class I-III reservoirs. Natural gas hydrate in Class I reservoirs holds significant commercial potential, as demonstrated by production trials in the South China Sea. However, experimental studies have focused largely on Class III systems, with Class I/II reservoirs remaining underrepresented due to the difficulties in simulating the geothermal gradient and interlayer interactions. This study investigates depressurization performance across all three classes using a novel 360° rotatable reactor with segmented temperature control, enabling precise simulation of reservoir conditions. Results reveal: (i) Class I shows two-stage gas production, with 50% from early free gas enabling rapid depressurization, followed by dissociated gas dominance. They achieve 38.4%–78.3% higher cumulative production and superior gas-to-water ratios due to efficient energy use. (ii) The free gas layer in Class I accelerates pressure and heat transfer. Class II’s water layer provides sensible heat but causes water blocking, impairing heat flow. Class III exhibits rapid initial dissociation but a quick decline without fluid support. (iii) Low temperature, low hydrate saturation, and high production pressure collectively reduce efficiency by increasing flow resistance, limiting gas supply, and reducing dissociation drive. Over-depressurization risks hydrate reformation and ice blockage. This work bridges experimental gaps for Class I/II reservoirs, offering key insights for optimizing recovery.