Shale gas reservoirs have different characteristics. In this chapter, these characteristics and different methods of characterization are discussed. First, well logging characterization methods such as well log data, seismic data, hybrid workflow, and seismic waveform are explained. In the section “Petrophysical Characteristics of Gas Shales,” different major sources to attain information are described. The thermal property, viscosity, density, and composition of shale gas are then discussed.