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Low porosity and permeability of Marcellus and Utica shale often limit the hydrocarbon recovery. To increase shale porosity, hydrothermal deformation (HTD) of Marcellus shale was performed and the effects of subcritical water temperature and reaction time on porosity were evaluated. HTD experiments were performed at the water saturation pressure (225.3, 576.8, and 1245.5 psi) for corresponding water temperature at 200, 250 and 300 °C for one, three and six hours of residence time. Low-temperature N2 adsorption was used for the porosity measurement of raw and treated shales. Furthermore, the morphology of raw and HTD shale samples was analyzed with scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction analyzer (XRD). It was observed that shale porosity was significantly enhanced by HTD conditions. For instance, HTD at 300 °C (1245.5 psi) for six hours of residence time, shale porosity increased more than four times compared to raw shale. This porosity was attributed to leaching of calcite, clay, and quartz, which was confirmed by analyzing HTD process liquids by Induced Coupled Plasma-Optical Emission Spectroscopy (ICP-OES).Shale permeability depends on the width of fracture aperture. HTD experiments of Utica shale core plugs were performed and the changes in the fracture aperture widths were observed with respect to HTD reaction conditions. Digital microscope was used to measure the fracture aperture width and it was observed that fracture aperture width was increased with the increase in HTD temperature and pressure. For example, HTD at 300 °C (1245.5 psi) for three hours residence time, fracture aperture width increased more than seven times compared to raw shales. Micro-fracture permeability for the raw and HTD shales was also estimated by using conceptual matchsticks model. Micro-fracture permeability was also increased with the increase in HTD temperature. Micro computed tomography (micro-CT)-scan was used to observe the fracture propagation along with the shale core plugs. Avizo 9.3 was used to analyze the micro CT-scan images. In summary, this study investigated the changes in connectivity of shale porous structure by observing the changes in shale porosity and fracture aperture with the influences of subcritical water treatment. A conceptual matchsticks model was also used to estimate the micro-fracture permeability of shale. Finally, in terms of pre-feasibility study, an economic estimation was made considering expected case and the worst case scenarios for the developed process model for hydrothermal fracking. Broader picture of this study is to contribute in the improvement of hydraulic fracturing by introducing hydrothermal fracking. To extend this research works further in future, detail techno-economic analysis can be performed to evaluate the feasibility of hydrothermal fracking.

Using well logs and AVO gradient analysis, I identify and characterize a package of reflectors associated with the Utica Shale from vibroseis data collected by Wright State University at the Gabor Gas Storage field near Canton, Ohio. I also correlate TOC measurements from wells to densities and velocities at the same depths. On the seismic data, I interpret prominent reflections from the top and bottom of the Utica Shale and an intra-Utica reflector of varying frequency content associated with a velocity/density low in well log data. I investigate the possibility that the lateral variation in frequency content and change in wavelet character of these reflections is influenced by velocity gradients, termed Wolf Ramps. A Matlab software script was written in order to approximate this behavior using synthetic wavelets, and the resulting model matched well with the seismic data. Additionally, I note a possible reverse fault within the Utica that could create fracture porosity and a migration pathway. To model the AVO response, an AVA volume was created from prestack data and reflection coefficients up to 30 degrees of incidence were calculated using the two-term Aki-Richards approximation. Large negative normal incidence reflection coefficients attenuated at higher angles of incidence (Class IV anomalies) were observed at the top of Utica reflector, a response consistent with a change from silica-rich nonsource shale to black source shale. Large positive normal incidence reflection coefficients decreasing at higher angles of incidence (Class I anomalies) were noted at the bottom of Utica reflector, consistent with a shift from low impedance source shale to higher impedance calcareous shale.To perform forward modeling, I used geophysical well logs and NS-EW vibroseis line data. Using Hampson Russell commercial software, acoustic impedance and reflectivity were computed from sonic and density logs. An average wavelet at the Utica two-way travel time was extracted using Promax software and convolved with the reflectivity to create a synthetic seismogram for each well. Lastly, the Utica Shale and underlying formations were correlated in Petrel software using well logs in the vicinity of the seismic lines. The results of the correlation allowed me to make connections between the depositional processes that led to the formation of the Ohio Utica from the New York Utica, for which outcrops and a large number of well logs are available.