Ultrasonic velocity and mechanical anisotropy of synthetic shale with different types of clay minerals

Abstract

Clay minerals are the most abundant materials in shale. Their presence significantly influences the elastic behavior of reservoir rocks as a function of mineral type, volume, and distribution, and their orientation controls the shale’s intrinsic anisotropic behaviors. Thus, knowing the elastic properties of shale with different types of clay minerals is imperative for fully understanding the seismic properties of the reservoir. However, it is extremely difficult to measure the elastic properties of natural shale by means of a single variable (in this case, the type of clay), due to the influences of multiple factors, including water, total organic carbon content, complex mineral composition, and so on. Thus, we use quartz, clay (kaolinite, illite, and smectite), carbonate, and kerogen extract as the primary materials to construct synthetic shale with different types of clay. Ultrasonic experiments were conducted to study the anisotropy of velocity and mechanical properties (Young’s modulus and Poisson’s ratio) in dry synthetic shale samples as a function of applied axial stress. The results show that the velocity of samples increases with applied pressure and the rate of velocity increase is higher at low pressures. Similarly, the dynamic Young’s modulus and Poisson’s ratio increase with applied pressure; [Formula: see text] is always larger than [Formula: see text], but [Formula: see text] may be larger or smaller than [Formula: see text]. Furthermore, velocity anisotropy and mechanical anisotropy decrease with the increase of stress and are sensitive to stress and lithology. The closure of large aspect-ratio pores (and/or microcracks) seems to be a dominant mechanism controlling the change of anisotropy. Finally, the changes in mechanical anisotropy under applied stress are larger compared with the changes in velocity anisotropy, indicating that mechanical properties are more sensitive to the changes in rock property.

Applied techniques for residual oil recovery from source rocks: A review of current challenges and possible developments

“…Furthermore, the use of SCFs, especially CO 2 , combined with other fluids such as steam and N 2 to minimize cost and improve recovery. In the literature, lab/pilot plant to field Supercritical CO 2 and iso-propanol 70 14.47 Shang et al [80] Supercritical CO 2 110 30 Zhu et al [81] Supercritical CO 2 71 60 Kurz et al [82] Supercritical water extraction 374 21 Chham et al [83] Supercritical toluene 320 4.5 Chham et a [83] Supercritical methanol/ethanol 320 20 Marcus [84] Supercritical CO 2 80 20 Pan et al [85] Supercritical CO 2 110 34.5 Jin et al [86] Supercritical CO 2 110 50, 60, and 65 Rudyk et al [87] Experimental and simulated Sc-CO 2 extraction 45 5-17 Wang et al [88] Supercritical organic solvents (isopropanol and hexane) 279 and 225 5.4 and 2.9 Imanbayev et al [89] scale-up studies are limited to illustrate the technical feasibility and applicability in the field. The use of CO 2 gas is considered cost-effective and eco-friendly if postprocessing, including sequestration and storage of feedstock, are considered.…”

“…[18] Ultrasonic-assisted waves extraction, which has been investigated and applied in many reports, [19,20] provides advanced benefits such as initial and operational cost reduction, elimination of produced water and other harmful chemicals, and effective processing time compared to other extraction techniques. [21] Source rock extraction with microwave-assisted pyrolysis (MWAP) was studied as another potential method for unconventional applications. [22,23] Several studies have been conducted on shale formations transparency to microwave radiations, which is subject to organic matter heterogeneous distribution.…”

Vertical velocity at hydrostatic and anisotropic stresses

“…Recent publications by Gong et al (2018) and Ramos et al (2019) explore, experimentally and theoretically, the effects of clay mineralogy and lamination, respectively, on elastic anisotropy in shale samples. Let us also bring the reader's attention to a recent important publication by Barbosa et al (2019), where the authors estimate fracture compliance from attenuation and velocity analysis using full-waveform wireline data.…”