LAUSR

Abstract Adsorbed and free methane are the primary contributor for gas production from shale. To accurately quantify the multiphase methane in shale is of great significance for shale gas exploration and exploitation. The conventional calculation methods to quantify the multiphase methane in shale are typically mathematical extrapolation from reservoir information, which tend to generate large error and is hard to be applied for shale reservoir because of its heterogeneity characteristics. Meanwhile, the most commonly used volumetric or manometric experimental methods are tedious, time-consuming and indirect measurement that requires assuming adsorbed phase density. Any volumetric effect or impurities can distort the shape of the isotherm measured with volumetric or manometric method. Therefore, it is necessary to explore a new quantitative method that can directly detect the multiphase methane in shale. In this study, several special experimental setups and methods were designed to evaluate the multiphase methane in shale. By introducing the low-field nuclear magnetic resonance (NMR) into the isothermal methane adsorption experiments of shale samples, this study developed a methodology for quantitative identification of multiphase methane gases in shale. Results show that the transverse relaxation time (T2) spectra of methane in shale contain four distinctive peaks, among which the peak (P1) with shortest T2 (