Main models and distribution patterns of gas reservoirs in large-medium gas fields of China

Based on characteristics and trap types of gas reservoirs in large and medium gas fields in China, 4 gas reservoir models have been established: (i) structural trap gas reservoir model I, formed earlier than or simutaneously with generating of gases; (ii) structural trap gas reservoir model II, formed later than generating of gases; (iii) fossil weathered residuum gas reservoir model; and (iv) mud diapir abnormal temperature and pressure gas reservoir model. Distribution patterns of large-medium gas fields are described with the concept of ''sealed compartment'' It is concluded that the inner-compartment area, marginal area of the compartment and the areas between two overlapped sealed compartments are the most favourable areas for discovering large-medium gas fields.