Kinetic Parameters of Methane Generated from Source Rocks in the Kuqa Depression of Tarim Basin and Their Application

In a thermal simulation experiment of gold tubes of closed-system,calculating with the KINETICS and GOR-ISOTOPE KINETICS software,kinetic parameters of gas generation and methane carbon isotopic fractionation from Triassic-Jurassic hydrocarbon source rocks in the Kuqa depression of Tarim Basin are obtained.The activation energies of methane generated from Jurassic coal,Jurassic mudstone and Triassic mudstone in the Kuqa Depression are 197-268 kJ/mol,180-260 kJ/mol and 214-289 kJ/mol,respectively,and their frequency factors are 5.265x10~(13)s~(-1),9.761x10n~(11)s~(-1) and 2.270x10~(14)s~(-1).This reflects their differences of hydrocarbon generation behaviors.The kinetic parameters of methane carbon isotopic fractionation are also different in Jurassic coal,Jurassic mudstone and Triassic mudstone,whose average activation energies are 228 kJ/mol,205 kJ/mol and 231 kJ/mol,respectively.Combined with the geological background,the origin of natural gas in the Yinan-2 gas pool is discussed,and an accumulation model of natural gas is thus established.The Yinan- 2 gas is primarily derived from Jurassic coal-bearing source rocks in the Yangxia Sag.Main gas accumulation time is 5-0 Ma and the corresponding Ro is in the range from 1.25%-1.95%.The loss rate of natural gas is 25%-30%.