Current industry criteria for geothermal-reservoir classification were established for high-quality hydrothermal systems (medium–high porosity and permeability). Consequently

most Chinese basinal reservoirs exhibit medium to low porosity and low permeability are misclassified as "poor

" rendering the standards inapplicable. Moreover

the multi-parameter methods commonly used in pre-feasibility assessments require extensive data sets that are seldom

available during early exploration phases. Rapid

low-parameter evaluation protocols are therefore urgently needed. ObjectiveHydrothermal sandstone reservoirs in the Songliao Basin's key oil-producing area are typified by medium–thin beds

medium–low porosity

and low permeability. These characteri-stics are traditionally labelled as "poor." Using these reservoirs as a case study

we recalibrate the classification criteria for low-quality hydrothermal systems and develop parsimonious

rapid-assessment protocols that minimize data requirements. MethodsFirst

the fundamental reservoir characteristics (thickness

porosity

and permeability) were statistically analyzed. The Golden Section Method was applied to classify parameter levels and establish evaluation criteria. Second

given the limited temperature variation among the studied low-temperature geothermal reservoirs

single-well daily production rate emerged as a critical evaluation metric. Consequently

sand body thickness

porosity

permeability

and single-well daily production rate within the study area were selected as input variables. Multivariate linear regression analysis was employed to derive a geothermal reservoir evaluation formula. This formula was then used to calculate evaluation unit scores

with final grading established using the Golden Section Method. ResultsPairwise comparison of the score rankings from this method against those of two established evaluation methods demonstrated the validity of incorporating sand body thickness while excluding temperature. Furthermore

the relatively high standard deviation of the scores obtained by this method enhances its ability to delineate variations among the evaluation units. Consequently

this approach demonstrates greater feasibility

and the formulated evaluation criteria are particularly well-suited for hydrothermal reservoirs with limited storage capacity. ConclusionThe evaluation criteria for low-storage hydrothermal systems developed in this study provide a valuable reference for geothermal-reservoir assessment in other basins. While basin-specific heterogeneity limits the direct transferability of the concise

few-parameter rapid-assessment model

the methodological framework used to derive the evaluation equation offers a robust

replicable template for analogous studies.