Abstract: Systems and methods for modeling gas desorption in a subterranean reservoir include measuring a gas sorption parameter using a crushed core sample from the subterranean reservoir; computing a gas storage capacity of the subterranean reservoir at an initial reservoir pressure based on the gas sorption parameter; generating a three-dimensional (3D) distribution of total organic carbon (TOC) in the subterranean reservoir; estimating a 3D distribution of original adsorbed gas in place of the subterranean reservoir by correlating the gas storage capacity with the 3D distribution of TOC; and predicting the amount of gas desorbed from the subterranean reservoir as the reservoir is depleted.

Abstract: Systems and methods for modeling gas desorption in a subterranean reservoir include measuring a gas sorption parameter using a crushed core sample from the subterranean reservoir; computing a gas storage capacity of the subterranean reservoir at an initial reservoir pressure based on the gas sorption parameter; generating a three-dimensional (3D) distribution of total organic carbon (TOC) in the subterranean reservoir; estimating a 3D distribution of original adsorbed gas in place of the subterranean reservoir by correlating the gas storage capacity with the 3D distribution of TOC; and predicting the amount of gas desorbed from the subterranean reservoir as the reservoir is depleted.

Abstract: Methods and systems for determining an estimated reservoir property using a determined desorption stage are disclosed. The method includes determining a fluid property and composition of a first fluid sample obtained from a reservoir, determining a measured relative volume of gas components and isotope ratios of gas components of the sample, and determining an equation of state. The method also includes obtaining a second and third sample at two later times, determining a composition, a measured relative volume of gas components, and isotope ratios of gas components of the later samples, and calibrating the equation of state utilizing the fluid composition and measured relative volume of gas components. The method further includes predicting a relative volume of gas components from the equation of state, determining a desorption stage, determining a critical pressure, an extent of desorption and a quantity of produced desorbed gas and determining the estimated reservoir property.