Mudrock Components and the Genesis of Bulk Rock Properties

Chemical and Reactive Transport Processes Associated with Hydraulic Fracturing of Unconventional Oil/Gas Shales

“…Most black shales were deposited in marine environments and together with coal, their nonmarine analogues, comprise the most important accessible reservoir of organic matter in Earth's crust. 6 Readers interested in the geologic history of unconventional oil/gas shales in the U.S. can find a detailed discussion of their depositional settings in Milliken and Hayman (2020) 7 (see their Table 1.1). For example, the Marcellus shale, located in the Appalachian Basin, Pennsylvania, USA, was formed during the Devonian period (419 to 444 MY) in a foreland basin, a structural basin that develops adjacent and parallel to a mountain belt.…”

“…46,47 Characterization studies of shales and mudstones using these and other methods have shown that they are not homogeneous and that their permeabilities vary by 13−15 orders of magnitude. 7 A comparison of the average mineralogy of shales with that of igneous rocks and sandstones by Rimstidt et al (2017) 24 shows that chemical weathering of igneous rocks converts a major fraction of aluminosilicate minerals such as feldspar (plagioclase and K-feldspar) and mica (biotite and muscovite) into clay minerals (Figure 10). As shown in this figure, a fraction of the quartz and feldspar in igneous rocks survives chemical weathering and is incorporated into shales and sandstones.…”

“…The fine-grained nature of mudstones and shales, with >50% of their particles <62.5 μm in diameter, has made them difficult to characterize mineralogically and texturally (Milliken and Hayman, 2020) . In spite of this difficulty, however, a great deal has been learned over the past few decades about their mineralogy, organic matter, and textures at spatial scales ranging from nanometers to millimeters. ,− The analytical and structural methods used for these studies include powder X-ray diffraction and Rietveld analysis, , synchrotron-based X-ray absorption spectroscopy (XAS) and micro-X-ray fluorescence imaging of element distributions (μ-XRF), , electron microprobe analysis and backscattered electron imaging, , X-ray computed tomography (X-CT), , small-angle X-ray and small-angle neutron scattering, ,− attenuated total reflectance (ATR) FTIR spectroscopy, 13 C NMR, − SIMS, and electron microscopy methods, , including modern ion milling techniques to produce very thin samples with flat surfaces and little mechanical damage. , Characterization studies of shales and mudstones using these and other methods have shown that they are not homogeneous and that their permeabilities vary by 13–15 orders of magnitude …”

Multi-physics evaluation of carbonate-rich source rocks from high-resolution images

“…Scanning Electron Microscopy (SEM) is commonly used for source rock characterization. [9][10][11][12] High-resolution twodimensional (2D) images of the complex, nanometer-scale, heterogeneity of source rocks are taken at the length scale of the heterogeneity of the rock fabric and pore space. These high-resolution images provide important context to evaluate the potential of unconventional reservoirs.…”