Abstract: 47 large and medium gas fields in China is based on low abundance of reserves, the second is high and middle abundance of reserves, and the least is ultra-low reserves. The method of estimating gas diffusion loss is set up by using the Fick?s law, and the gas diffusion loss of the 47 gas fields is estimated. Results show that the diffusion loss of different gas fields varies a lot. The minimum is only 0.92×108m3, while the maximum is 2286.81× 108m3. The latter is over 2200 times higher than the former. Through the research on the correlation between reserves abundance and diffusion loss of gas in the 47 gas fields, it is shown that the lower gas reserves abundance is, the greater gas diffusion loss gets, and vice versa. Gas diffusion loss is an important cause of the decrease of gas reserves abundance of large and medium gas fields in China.

Key words: large and medium gas fields, natural gas, diffusion and loss, reserves abundance, quantitative research