Gas shales are different from conventional reservoir as the strata are both source rock and reservoir rock for gas, and no structural or stratigraphic traps are needed to retain the gas. The recent advances in horizontal drilling and hydraulic fracturing stimulations have made vast shale gas resource commercially viable. However, due to the complex nature of gas storage, the quantification of shale gas reservoirs has been proven extremely challenging. Shale formation is usually extremely tight and the majority of the pores are nano-pores in which the diameters of the pores are in the range of several nanometers to tenth of nanometers. In this research, we propose to perform the numerical sensitivity study of nanopore structures on fluid flow. The proposed research will involve: Generation of 3-dimensional digital core of nano-pore structures based on the Scanning Electron Microscope (SEM) images of real core samples that are collected from the Longmaxi Formation - Lower Silurian Marine Shale Gas Play in Southern China. The results indicate that digital core is an efficient way to characterize the micropores structure of the shale formation parameters.

"Determining shale gas petrophysical properties is the cornerstone to any reservoir-management practice. Hitherto, conventional core analyses are inadequate to attain the petrophysical properties of shale gas at submicron-scale. This study combines interdisciplinary techniques from material science, petrophysics, and geochemistry to characterize different shale gas samples from North America including Utica, Haynesville and Fayetteville shale gas plays. Submicron pore structure, clay mineralogy, wettability and organic matter maturation were investigated to evaluate the petrophysical properties of shale gas rocks and to determine the impact of organic and inorganic matters on wettability alteration for different fracturing fluids on shale gas rocks. High pressure (up to 60,000 psi) mercury porosimetry analysis (MICP) determined the pore size distributions. A robust detailed sequential milling and imaging procedure using dual beam (SEM/FIB) instrument was implemented successfully to characterize the submicron-pore structures. Various types of porosities were observed on SEM images. Pores were found in organic matters with the size of nano level and occupied 40-50% of the kerogen body. The reconstructed 3D pore model provided key insights into the petrophysical properties of shale gas such as pore size histogram, porosity, tortuosity and anisotropy, etc. X-ray diffraction (XRD) analysis showed high illite content in Haynesville shale. It also suggested high calcite content in Utica shale samples. Wettability tests showed that most of the additives that were used can alter shale gas surfaces toward hydrophilic-like system (water-wet). Moreover, palynofacies analysis provided valuable information about kerogen type and its degree of thermal maturation, which are key parameters in shale gas exploration"--Abstract, p. iii.

The need for energy is increasing and but the production from conventional reservoirs is declining quickly. This requires an economically and technically feasible source of energy for the coming years. Among some alternative future energy solutions, the most reasonable source is from unconventional reservoirs. As the name “unconventional” implies, different and challenging approaches are required to characterize and develop these resources. This Special Issue covers some of the technical challenges for developing unconventional energy sources from shale gas/oil, tight gas sand, and coalbed methane.