Abstract: Systems, methods, and devices for quantitatively identifying gas zones irrespective of porosity or lithology using nuclear downhole tools are provided. In particular, because some formation materials such as shales can confound some conventional measurements, a gas detection measurement may be obtained that can be used to qualitatively identify gas zones. The gas detection measurement may be based at least partly on a relationship between inelastic gamma rays, neutron capture gamma rays, and experimental or modeled formation data, such that the gas detection measurement qualitatively indicates a gas zone when a gas zone is present in a formation irrespective of a lithology or a porosity of the formation.

Abstract: A logging tool capable of making different types of measurements is provided, and a plurality of measurements on a formation are obtained. Certain mineral properties of the formation are assumed and a mixed properties theorem for the formation is invoked. Upper and lower velocity limits for sonic waves traveling through the formation are determined using the above information. Biot's constant is also computed using the above information. LWD data on the formation is obtained and an effective stress is determined. A total stress is determined and, from that and the other information, a pore pressure is determined.

Abstract: Systems, methods, and devices for quantatively identifying gas zones irrespective of porosity or lithology using nuclear downhole tools are provided. In particular, because some formation materials such as shales can confound some conventional measurements, a gas detection measurement may be obtained that can be used to qualitatively identify gas zones. The as detection measurement may be based at least partly on a relationship between inelastic gamma rays, neutron capture gamma rays, and experimental or modeled formation data, such that the gas detection measurement qualitatively indicates a gas zone when a gas zone is present in a formation irrespective of a lithology or a porosity of the formation.

Abstract: A logging tool capable of making different types of measurements is provided, and a plurality of measurements on a formation are obtained. Certain mineral properties of the formation are assumed and a mixed properties theorem for the formation is invoked. Upper and lower velocity limits for sonic waves traveling through the formation are determined using the above information. Biot's constant is also computed using the above information. LWD data on the formation is obtained and an effective stress is determined. A total stress is determined and, from that and the other information, a pore pressure is determined.