Abstract:

According to the principle that generated hydrocarbon minus residual hydrocarbon equals to the amount of expelled hydrocarbon which is expressed by the theory of hydrocarbon expulsion threshold controlling the distribution of oil and gas, and based on the amount of oil and gas calculated by the model of chemical kinetics using the samples of Tarim Basin and the amount of residual oil and gas calculated by the statistical model, the amount of oil and gas expelled from mudstone is calcuulated quantitatively and their relationship with the abundance, types and maturity of organic matter is discussed, The corresponding distinguishing plates are established. The results indicate that the low limit of organic carbon abundance for mud gas source rock is about 0.1%. This is much lower than that of oil sourcemek(TOC=0.4%). This implies that a lot of mudstones which are regarded as non-source rocks according to the distinguishing criteria of oil source rock may be potential gas source rocks.

Key words: gas source rock, gas expulsion, organic matter abundance, organic matter types, maturity