摘要：Methane gas is the primary focus of geochemi- cal studies regarding coal seam gas (CSG). To study the fractionation of carbon isotopes that occurs dur- ing CSG desorption from coal rocks, a wireline core sample was collected and placed inside a homemade airtight CSG /shale gas desorption cannister, where it was allowed to continue desorbing CSG. Two-hun- dred and fifty milliliters of CSG samples were col- lected for carbon isotope analysis. The experimental results indicate that 813CI increases slowly duringthe early stages of CSG desorption. ö13CI increased dramatically after a certain volume of gas was de- sorbed from the sample. Toward the end of the de-sorption process, the increase in ó13C1 over time slowed significantly. Given a fixed desorption tem- perature, the 613CI of the desorbed CSG can in- crease over time; this growth is initially slow, then becomes fast, and finally becomes slow. In most cases, CSG samples from the early stages of the de- sorption process will exhibit slightly lower 813C1 values than the CSG's actual 613CI value. Therefore, sampling time is a factor that must be considered in studies about the horizontal distribution, genesis, and fractionation mechanisms of CSG methane ö13C1 values.
