The mature organic-rich source rocks that have expelled much of the hydrocarbons that have been produced from conventional reservoirs in the U.S. now represent both developed reserves and potential resources for the future.  Shale gas has become an attractive target for numerous operators because it represents a huge resource (500 to 780 TCF), and higher gas prices have lessened the economic challenges for its development.  If these formations can be economically developed, many thousands of wells will be drilled during the next decade.

Key reservoir parameters for shale gas deposits include: 1) thermal maturity, 2) adsorbed gas fraction, 3) reservoir thickness, 4) TOC, and 5) free gas fraction within the pores and fractures.  A comprehensive shale gas log evaluation requires a calibration to core for thermal maturity and a metric to equate TOC to adsorbed gas. This presentation will discuss the importance of each of these reservoir parameters, aswell as describe a robust shale gas interpretation process utilizing an  integrated wireline logging tool and neutron-induced gamma ray capture spectroscopy.  This process provides gamma ray independent clay content plus a matrix density that compensates for the variable lithology typical of gas shale.  Advanced log analysis is used to quantify kerogen,this value is converted to TOC based on thermal maturity, and the Langmuir isotherms are used to calculate adsorbed gas.  Porosity and gas saturations are calculated, and the free gas volume is converted to SCF/ton at reservoir conditions.  Cumulative adsorbed and free gas is reported in BCF/section. This provides critical information as to the richness of the shale resource that can then be used to evaluate completion effectiveness.