ISO 18871:2015 provides methodology for measuring coalbed methane content of coal core samples obtained by coring or sidewall coring during well drilling. It shall be also applied to drill cuttings samples, if the equipment for the determination of the coalbed methane content according to a respective national standard is not available. The selection of the most appropriate method shall consider the purpose of the test and the possibilities of sampling.
ISO 18871:2015 is applicable for the direct method of measuring coalbed methane content. It includes sample preparation, experimental procedures and calculation methods. Indirect methods of measuring gas content of coal (not included in this standard) are generally based on either the gas sorption characteristics of coal under defined/specified pressure and temperature conditions.
ISO 18871:2015 includes three types of direct measuring methods: conventional desorption (slow desorption) of core samples, fast desorption of core samples, fast desorption of cuttings or lump samples. The difference among them lies in the time allowed for gas to desorb before final crushing and in sample size and shape.
ISO 18871:2015 is applicable for the determination of the methane content of coal during coal and coalbed methane exploration for the determination of free gas content of low rank coals is included.