Аналіз ландшафтного різноманіття Миколаївської області

Groundwater systems are increasingly used for seasonal aquifer thermal energy storage (SATES) for periodic heating and cooling of buildings. Its use is hampered in contaminated aquifers because of the potential environmental risks associated with the spreading of contaminated groundwater, but positive side effects, such as enhanced contaminant remediation, might also occur. A first reactive transport study is presented to assess the effect of SATES on the fate of chlorinated solvents by means of scenario modeling, with emphasis on the effects of transient SATES pumping and applicable kinetic degradation regime. Temperature effects on physical, chemical, and biological reactions were excluded as calculations and initial simulations showed that the small temperature range commonly involved (ΔT < 15 °C) only caused minor effects. The results show that a significant decrease of the contaminant mass and (eventually) plume volume occurs when degradation is described as sediment-limited with a constant rate in space and time, provided that dense non-aqueous phase liquid (DNAPL) is absent. However, in the presence of DNAPL dissolution, particularly when the dissolved contaminant reaches SATES wells, a considerably larger contaminant plume is created, depending on the balance between DNAPL dissolution and mass removal by degradation. Under conditions where degradation is contaminant-limited and degradation rates depend on contaminant concentrations in the aquifer, a SATES system does not result in enhanced remediation of a contaminant plume. Although field data are lacking and existing regulatory constraints do not yet permit the application of SATES in contaminated aquifers, reactive transport modeling provides a means of assessing the risks of SATES application in contaminated aquifers. The results from this study are considered to be a first step in identifying the subsurface conditions under which SATES can be applied in a safe or even beneficial manner

Measuring intergranular force in granular media

A new method is proposed to measure intergranular forces in granular geomaterial from time-lapsehigh-resolution X-ray computed tomographyimaging using a grain trackingapproachand discrete element metho

Проблеми становлення і розвитку інформаційного законодавства в контексті євроінтеграції України

Щодо розвитку права і правової науки в інформаційній сфері в Україні.О развитии права и правовой науки в информационной сфере в Украине.On the development of law and law science in the informative sphere of Ukraine

Micromechanics of High-Pressure Compaction in Granular Quartz Aggregates

The mechanical behavior of porous sandstones is generally modeled using concepts from granular mechanics, often overlooking the effect of cementation. To probe the key differences between sand and sandstone mechanics, we performed triaxial deformation experiments on Ottawa quartz sand at 5- to 40 MPa effective confining pressure. At 5 MPa, the samples are able to dilate. At higher confinement, the aggregates show continuous compaction, displaying strain hardening. The stress-strain behavior is nonlinear, and the exact onset of inelastic compaction could not be determined accurately. Measured P-wave velocities show the development of anisotropy. With increasing axial strain, the along-axis velocities tend to increase, while velocities perpendicular to the compression axis tend to decrease (at low pressure) or remain constant (at high pressure). In samples deformed under elevated pressure conditions, acoustic emission event locations are diffuse. Microstructural investigations show an increase in grain chipping and crushing with increasing confining pressure, but no evidence of localized compaction could be observed. The nature of the pore fluid, either decane or water, does not significantly influence the mechanical behavior at strain rates of 10−6 to 10−4 s−1. Grain angularity and grain-size distribution also did not significantly change the mechanical behavior. We infer that our observations indicate that the lack of cementation introduces additional degrees of freedom for grains to slide, rotate, and reorganize at the sample scale, precluding the existence and sustainability of stress concentrations beyond the grain scale. This results in progressive compaction and hardening, and lack of compaction localization

Апеляційний перегляд постанов місцевого суду, винесених за розглядом скарг на постанову про порушення кримінальної справи

Досліджуються основні проблеми апеляційної перевірки правомірності порушення кримінальної справи.Исследованы основные проблемы апелляционной проверки правомерности возбуж­дения уголовного дела.The article is dedicated to the main problems of the appellate review of instituting pros­ecution

The thermal properties of set Portland cements – a literature review in the context of CO2 injection well integrity

Depleted hydrocarbon reservoirs are a promising target for CO2 sequestration. Injection of cold CO2 into such geological reservoirs will cause thermal stresses and strains in wellbore casings, cement seals and surrounding rock, which may lead to the creation of unwanted pathways for seepage. Joule-Thomson effects could potentially produce freezing conditions. The design of CO2 injector wells must be able to cope with these thermal loads. While numerical modelling can be used to develop our understanding and assess the impact of thermal processes on wellbore integrity, such analyses require reliable input data for material properties, such as those of the cement seals. This critical review provides an overview of existing lab measurements and theoretical considerations to help constrain the thermal behaviour of Portland cement under relevant subsurface conditions. Special attention is given to the i) thermal conductivity, ii) specific heat capacity, and iii) coefficient of thermal expansion. Influences on these properties of factors such as a) temperature, b) pressure, c) mixing water-to-cement ratio, d) extent of hydration, e) porosity, and f) pore fluid saturation are discussed. Our review has shown that lab datasets obtained under relevant downhole conditions are limited, constraining the input for numerical assessment of wellbore cement integrity

Impact of humid supercritical CO2 flow and CO2 solvation-induced cement porewater expulsion on reactive self-sealing processes along wellbore microannuli

Ensuring geological containment of injected CO2 is a key requirement in the planning and execution of Carbon Capture and Storage (CCS) projects. This includes a proper analysis, and if needed remediation, of the wellbore cement sealing integrity. Defects like casing-cement microannuli can impair this sealing integrity, especially if they expose the cement to flowing CO2-rich fluids. Chemical reaction between the cement and CO2 could in specific cases potentially enlarge seepage pathways, while in others reaction may seal off pathways via carbonate precipitation. Previous studies focused on these reactive transport processes during flow of CO2-rich brine, demonstrating small cement defects possess some definite capacity to self-seal. While this earlier work produced valuable insight, water-based flow experiments are not fully representative for CO2 seepage along real CCS wells. Actual seepage flows will likely be buoyancy-driven and consist mainly of humid CO2 (in its gaseous, liquid, or supercritical phase) rather than carbonated brine. Humid CO2 and carbonated brine have very different fluid properties, e.g., in terms of mineral solubility, which could profoundly change dissolution-precipitation processes and their impact on CCS well integrity. This study presents the first reactive flow-through experiments performed using humid CO2 as the flowing medium, allowing us to assess how the effective permeability of 2–20 μm wide casing-cement microannuli evolves under multiphase CO2 reactive transport at 60 °C and 7–9 MPa pressure. After reference measurements using humid N2, the results show that exposure to humid CO2 can produce large reductions in defect effective permeability, with all samples reaching down to intact cement values. However, the overall reaction extent and amount of precipitation observed were limited compared to earlier flow experiments using carbonated brine. It is inferred that part of the observed reductions in flowrate likely occurred due to a shift in multiphase flow dynamics upon switching from humid N2 to CO2-based flow. Despite these differences, previously established self-sealing criteria for cement defects under carbonate brine flow seem to hold for humid CO2 flow to within current experimental uncertainty

Mechanical weakening of a mudrock seal by reaction with CO2-charged fluids

The long-term interaction of CO2-charged fluids with low permeability cap rocks is important for seal integrity assessment. To address this potential risk, we studied long-term geomechanical changes in a reservoir seal due to fluid-rock interactions with CO2-charged fluids, focusing on a natural CO2 analogue near Green River, Utah, USA. The observed chemo-mechanical changes are on the millimeter scale, which required small-scale petrophysical, mineralogical, and micromechanical analyses. Results showed that over the 7 cm thick reaction front, the low permeability cap rock underwent mechanical weakening, as indicated by indentation tests. This weakening is inferred to be due to dissolution of dolomite and hematite, with the former leading to porosity increase, as shown by small-angle neutron scattering, while the latter likely led to loss of electrostatic forces between the clay particles. This resulted in loss of cohesion, compaction, and formation of bedding-parallel fractures. Microfracturing occurred in situ, as evidenced by fractures infilled with pyrite and gypsum. This study demonstrates that mechanical weakening of cap rocks might occur, but only over time scales of ∼100,000 yr and over small distances. Considering the thickness of cap rocks above CO2 storage reservoirs, we do not anticipate a considerable threat of losing containment integrity over time scales of hundreds to thousands of years as a result of these small-scale fluid-rock interactions