Geophysical Responses of Organic-rich Shale and the Effect of Mineralogy

Total organic carbon (TOC) is one of the most important parameters for indicating the resource potential of unconventional shale reservoirs. Because of the low density and velocity of organic matter, some seismic attributes like P-wave impedance (Ip) and Vp/Vs ratio would respond to high TOC content. So we can use these seismic attributes to remotely identify organic-rich areas.

However, these attributes are not equally efficient for all shale formations. The behavior of the geophysical response on TOC content may vary due to mineral variations of different shale plays. So, it is important to understand the mineral composition, study their impact on geophysical responses, and choose the right seismic attributes for the interpretation of a certain shale play. A rock physics modeling can be applied to link the in-situ rock parameters like mineral composition, TOC content, porosity etc. with the geophysical response.

In this thesis work, I study the geophysical response of Barnett shale. In addition, I study the impacts of the mineral variations within an individual shale reservoir on geophysical response. Certain relationships between TOC and volume percentage of clay and quartz were observed, which should be taken into account when performing rock physics modeling, as opposed to assuming the mineral composition changing randomly.