Abstract: The proved reserves of offshore low permeability natural gas resources increase every year, in order to economical and efficient exploit this part of the reserves, reasonable classification is essential. Target is gas reservoirs in Huangliu Formation of the Dongfang area in Yinggehai Basin, propose six parameters classification method to evaluate offshore low permeability gas reservoir, such as open-flow potential per meter, permeability, the radius of main flow throat, movable fluid saturation, gas saturation and gas reservoir thickness. Thus, a comprehensive evaluation method for low permeability reservoirs is proposed. Considering the current offshore gas reservoir development characteristics, the correlation between the various classification parameters, the low permeability gas reservoir is subdivided into four subgroups. Meanwhile, the classification limit of each evaluation parameters is determined and different development recommendations are proposed for each subgroups of low permeability gas reservoir. The evaluation method refines the understanding of offshore low permeability gas reservoirs, avoids inaccurate classification results which occurred in using the same standard of classification for low permeability gas reservoirs, can better filter out the suitable for development gas reservoir under the current technology and economic conditions, also has certain reference significance to similar gas reservoir classification and evaluation.

Key words: offshore low permeability gas reservoir, gas reservoir classification, open-flow potential per meter, mainstream throat radius, movable fluid saturation, Yinggehai Basin