Kinetics Of Carbon Isotope Fractionation In The Process Of Organic Thermally Cracking Into Natural Gas And Its Application

In order to analyze the role of water playing in the pyrolysis process of organic matter and investigate how the added water quantity and quality affect the alkane gas carbon isotope fractionation, this paper adopts the gold tube pyrolysis setting, and select the pure n-C18H38 to add distilled water in different n-C18H38 to water ratio and to add three kinds of water with different quality in the same n-C18H38 to water ratio to perform experiments. Through new experiments and systematic analyses, we get something new and conclusions.(1)The added water increases the yield of hydrocarbon gas and stabililty. The increase yield of CO2 and H2 caused by reactions between CO and H2O and between C and H2O are excluded. Quantity of CO2 and H2 reflect that water reacts with the organic matter in the pyrolysis process. The more the water occupies in the reactants, the more obvious of the above effect. (2)The resolved inorganic salt in water can catalyze the organic matter to pyrolyze into alkane gases, CO2 and H2. (3)Water can affect methane isotope fractionation in the process of n-C18H38 pyrolysis, and the influence is small. So the difference is very small whether use organic thermally cracking experiments without water or with water to simulate carbon isotope fractionation of methane in geological condition, and the difference is also small if the kinetic parameters of carbon isotope fractionation were applied to geological conditions. (4)The carbon isotope fractionation of alkane gas is almost not changed by different quality water. (5)Compared to carbon isotope ration of alkane gas, the carbon isotope fractionation phenomena of CO2 does not exist obviously in the hydrous thermally cracking process.In order to avoid the influence to carbon isotope fractionation of alkane gas by the isotopic heterogeneity of reactants, five kinds of pure compounds that are n-C18H38, stearic acid, octadecylamine, decahydronaphthalene dekalin,9-phenyl anthrecene are selected to do thermally cracking experiments. By comparing and analyzing the influencing factors to carbon isotope fractionation of thermal cracking methane of organic matters are summarized as follows: (1)temperature. (2)the existing reaction mechanisms in the thermal cracking process of different compounds. (3)the carbon isotope ratio of the reactant.At the end the kinetic parameters of carbon isotope fractionation of methane calculated from the organic thermally cracking into methane experiments are simply applied to Xujiaweizi fault depression. The result is that 66% of the gas reservoir of Xushen 1 well is from the source rock near Xushen 1 well, and 34% is from the depocenter stratum.