Neutron scattering: A subsurface application review

Hosseini, Mirhasan; Arif, Muhammad; Keshavarz, Alireza; Iglauer, Stefan

doi:10.1016/j.earscirev.2021.103755

Cited by 36 publications

(8 citation statements)

References 236 publications

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“…79 In this study, we assumed two typical pore sizes for the capillary sealing efficiency analysis of the caprocks. Thus, full-scale pore and micro-fracture characterization of the caprocks using advanced techniques such as X-rays, infrared spectroscopy, and neutron scattering (NS) 80 are needed for future research to have a better understanding of their sealing efficiency. The effects of connectivity, maturity, and distribution of organic matter on caprock wettability and thus capillary sealing are other aspects for future research that need to be carefully examined.…”

Section: Discussionmentioning

confidence: 99%

Capillary Sealing Efficiency Analysis of Caprocks: Implication for Hydrogen Geological Storage

et al. 2022

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In hydrogen geological storage, capillary sealing efficiency analysis of caprocks is very important for containment security. In this work, the H2 wettabilities of three shales and one evaporite under various pressures (0.1, 5, 10, 15, and 20 MPa), temperatures (298 and 353 K), and organic acid concentrations (10–9 to 10–2 mol/L) were measured using the tilted plate method, and their effects on the capillary sealing efficiency of the caprocks were analyzed. Furthermore, two oil shales were tested to see the effect of their total organic content (TOC) on the wettability at two different pressure (5 and 15 MPa) and temperature (323 and 353 K) values since the TOC dramatically varies in shales and can significantly influence the wetting characteristics and, thus, the sealing efficiency. The results of this study indicate that the H2 wettability of the caprocks increased with pressure, organic acid concentration, and TOC but decreased with temperature. However, the sealing efficiency and H2 column height of the caprocks decreased with all the varying parameters but increased with temperature for oil shales. Furthermore, small pore sizes (i.e., r = 5 nm as a typical value for this study) and evaporites (e.g., gypsum) have the most efficient conditions for sealing for increased storage capacity. Overall, this work provides a deep understanding of the sealing efficiency of caprocks, which will aid in the successful implementation of hydrogen geo-storage and its associated structural trapping capacities.

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Section: Discussionmentioning

confidence: 99%

Capillary Sealing Efficiency Analysis of Caprocks: Implication for Hydrogen Geological Storage

et al. 2022

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“…Shale contains both the inorganic minerals (such as calcite, quartz, and clay) and organic matter (kerogen). The clays are typically composed of illites, kaolinites, chlorites, and montmorillonites. − Scientists have reported that MMT is an important component of caprock. , For instance, Tian et al reported that the compositional fraction of clay minerals reaches 66.71% in the caprock of Ordos Basin by volume; more precisely, montmorillonites account for 38.4% of the caprock. Therefore, we used MMT to mimic clay in the caprock.…”

Section: Models and Methodologymentioning

confidence: 99%

Hydrogen Diffusion in Clay Slit: Implications for the Geological Storage

et al. 2022

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We determined the self-diffusion coefficients of hydrogen in clay (montmorillonite) nanopores using molecular dynamics under subsurface conditions. We explored the effects of temperature, pressure, pore size, moisture content, and salinity. Our results show that the self-diffusion coefficient of hydrogen is on the order of magnitude of 10–8 m2/s. The diffusivity of confined hydrogen increases moderately with temperature and slit aperture but declines with pressure. The estimated density profile suggests that only one dense layer of hydrogen molecules is adsorbed near the slit surface. The distinct diffusion coefficients in the parallel and perpendicular directions to the basal surfaces confirm the confinement effect of the substrates. As the volume ratio of hydrogen increases, the existing pattern of hydrogen changes from a droplet to a layer sandwiched by the aqueous solution. The water bridge will act as a piston for the hydrogen droplet and impede hydrogen diffusion. However, when the hydrogen and brine form a stratified structure, the self-diffusion coefficient of hydrogen sandwiched by two brine films is similar to that of confined pure gas at the same pressure and temperature conditions. If the brine salinity reaches some extent, part of brine and hydrogen molecules will mix as a new phase, which slightly inhibits the hydrogen diffusion. This work provides a better insight into hydrogen diffusion through the clay nanopores, which is critical for reliably assessing the risk of hydrogen leakage through caprocks.

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“…Organic-hosted porosity is one of the most critical elements in successful shale plays. Different techniques viz., imaging (e.g., broad ion beam-scanning electron microscopy, and focused ion beam-scanning electron microscopy), gas adsorption (low pressure and high pressure gas adsorption techniques), mercury intrusion porosimetry, neutron scattering (e.g., ultrasmall/small angle neutron scattering), etc., are used to assess shale porosity. ,,,− In addition to several factors, such as the presence of surface functional groups, the mesopores and micropores, and the specific surface area, etc., thermal maturity levels have been identified to strongly control the development of organic porosity and, hence, the gas adsorption capacity of shales and carbonaceous matter. − Loucks et al observed organic nanopore development to be strongly dependent on the thermal maturity levels of the samples and inferred that this is essentially caused by the conversion of kerogen to hydrocarbons and the formation of pores within the organic matter in the process.…”

Section: Co2 Adsorption Versus Ch4 Desorption: Vis-à-vis Co2 Sequest...mentioning

confidence: 99%

Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration

et al. 2022

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Hydraulic fracturing has transformed the international energy landscape by becoming the go-to method for the exploitation of natural gas from unconventional shale reservoirs. However, in the recent years, the search for an alternative method of shale-gas exploration has intensified, because of various problems (e.g., contamination of ground and surface water, overexploitation of precious water resources, air pollution, etc.) associated with the usage of water-based fracturing techniques. The use of CO2 for shale gas exploitation has emerged as a better alternative to aqueous-based gas exploration techniques. CO2 when injected into deep shale reservoirs, transitions into supercritical CO2 (SC-CO2) when temperature and pressure condition exceeds the critical point, i.e., 31.1 °C and 7.38 MPa. In this paper, we comprehensively review the impact of SC-CO2 on shale gas reservoirs during the different stages of shale-gas exploration, i.e., (i) drilling, which involves the superiority of SC-CO2 over water-based drilling fluids, in terms of achieving under-balanced well condition, higher rates of penetration, and resistance to formation damage; (ii) fracturing, which involves factors affecting the tortuosity of fractures created by SC-CO2 fracturing, breakdown pressure, and proppant-carrying capacity; and (iii) injection, which involves the twin-headed benefit of enhanced recovery due to CO2/CH4 competitive adsorption and geological sequestration, CO2 vs CH4 excess sorption as a function of pressure, etc. Several research works have indicated discrepancies on how SC-CO2 impacts different shale properties. Some studies show low-pressure N2-gas-adsorption-derived surface area and total pore volume to be increasing with SC-CO2 imbibition, while others show a decreasing trend for the same. Similarly, for some shales, the quartz content, along with the clay mineral contents, decreased as the exposure to SC-CO2 increased, while in some other studies, with similar long-term exposure to SC-CO2, the quartz content was observed to increase along with the decrease in clay content and vice versa. Essentially, the increased exposure to SC-CO2 results in the dissolution of primary porous structures and fractures, and reformation of newer porous structure and conduits in shales. Nonetheless, these changes in the mineralogy weaken the microstructure of the rock bringing significant changes in the mechanical properties of the shales with implications on the wellbore stability and fracturing efficiency. The mechanical properties such as uniaxial compressive strength (UCS), Young’s modulus, and tensile strength decrease as the SC-CO2 saturation period increases. However, some studies have shown factors like bedding angle and phase-state of CO2 having varying effect on the strength behavior of the shales. Moreover, changes in the structure of shales caused by the creation of fractures and the reduction of their strength can also pose major risks, because of potential leakage of CO2 through these created pathways. How these processes would i...

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Neutron scattering: A subsurface application review

Cited by 36 publications

References 236 publications

Capillary Sealing Efficiency Analysis of Caprocks: Implication for Hydrogen Geological Storage

Capillary Sealing Efficiency Analysis of Caprocks: Implication for Hydrogen Geological Storage

Hydrogen Diffusion in Clay Slit: Implications for the Geological Storage

Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration

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Neutron scattering: A subsurface application review

Cited by 36 publications

References 236 publications

Capillary Sealing Efficiency Analysis of Caprocks: Implication for Hydrogen Geological Storage

Capillary Sealing Efficiency Analysis of Caprocks: Implication for Hydrogen Geological Storage

Hydrogen Diffusion in Clay Slit: Implications for the Geological Storage

Impact of Supercritical CO2 on Shale Reservoirs and Its Implication for CO2 Sequestration

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Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration