Abstract: A method for determining the gas pressure may include generating, via a downhole tool, neutron radiation in a cased wellbore of a geological formation and measuring a response to the neutron radiation. The method may also include determining, via a processor, at least one of a sigma, a neutron porosity, or a fast-neutron cross-section of the formation. Additionally, an equation of state of the gas may be estimated, and a gas pressure of the gas may be determined by solving a relationship, based at least in part on the equation of state, between the gas pressure and the at least one of the sigma, the neutron porosity, or the fast-neutron cross-section.

Abstract: A method for determining the gas pressure may include generating, via a downhole tool, neutron radiation in a cased wellbore of a geological formation and measuring a response to the neutron radiation. The method may also include determining, via a processor, at least one of a sigma, a neutron porosity, or a fast-neutron cross-section of the formation. Additionally, an equation of state of the gas may be estimated, and a gas pressure of the gas may be determined by solving a relationship, based at least in part on the equation of state, between the gas pressure and the at least one of the sigma, the neutron porosity, or the fast-neutron cross-section.

Abstract: Adsorbed gas in a formation may be estimated. Nuclear magnetic resonance (NMR) data for a subsurface geological formation is obtained, and at least a portion of the NMR data is corrected to produce corrected NMR data. A NMR-based estimate of formation porosity is determined using the corrected NMR data. Dielectric permittivity data for the subsurface geological formation is obtained, and a dielectric permittivity-based estimate of the formation water-filled porosity is determined using the dielectric permittivity data. A gas volume is determined using the determined NMR-based estimate of the formation porosity and the determined dielectric permittivity-based estimate of the formation water-filled porosity. The gas volume may be determined by subtracting the determined dielectric permittivity-based estimate of the formation water-filled porosity from the determined NMR-based estimate of the formation porosity. The gas volume per unit volume of the formation may be determined using an equation of state.

Abstract: Adsorbed gas in a formation may be estimated. Nuclear magnetic resonance (NMR) data for a subsurface geological formation is obtained, and at least a portion of the NMR data is corrected to produce corrected NMR data. A NMR-based estimate of formation porosity is determined using the corrected NMR data. Dielectric permittivity data for the subsurface geological formation is obtained, and a dielectric permittivity-based estimate of the formation water-filled porosity is determined using the dielectric permittivity data. A gas volume is determined using the determined NMR-based estimate of the formation porosity and the determined dielectric permittivity-based estimate of the formation water-filled porosity. The gas volume may be determined by subtracting the determined dielectric permittivity-based estimate of the formation water-filled porosity from the determined NMR-based estimate of the formation porosity. The gas volume per unit volume of the formation may be determined using an equation of state.