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

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

Observational evidence confirms modelling of the long-term integrity of CO2-reservoir caprocks

Anthropogenic CO2 storage, where CO2 is injected into saline geological resevoirs, relies on an impermeable caprock to seal in the CO2, but caprock reaction rates to CO2 acid brines are unclear

Observational evidence confirms modelling of the long-term integrity of CO2-reservoir caprocks

Storage of anthropogenic CO2 in geological formations relies on a caprock as the primary seal preventing buoyant super-critical CO2 escaping. Although natural CO2 reservoirs demonstrate that CO2 may be stored safely for millions of years, uncertainty remains in predicting how caprocks will react with CO2-bearing brines. This uncertainty poses a significant challenge to the risk assessment of geological carbon storage. Here we describe mineral reaction fronts in a CO2 reservoir-caprock system exposed to CO2 over a timescale comparable with that needed for geological carbon storage. The propagation of the reaction front is retarded by redox-sensitive mineral dissolution reactions and carbonate precipitation, which reduces its penetration into the caprock to ∼7 cm in ∼105 years. This distance is an order-of-magnitude smaller than previous predictions. The results attest to the significance of transport-limited reactions to the long-term integrity of sealing behaviour in caprocks exposed to CO2.Funding was provided by NERC to the CRIUS consortium (NE/F004699/1), Shell Global Solutions, for GR as part of the Center for Nanoscale Controls on Geologic CO₂ (NCGC), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award # DE-AC02-05CH11231, and DECC, which provided a CCS Innovation grant for completion of this work

Experimental and theoretical constraints on amino acid formation from PAHs in asteroidal settings

Laboratory astrophysics and astrochemistr

Effect of CO2-H2O-Smectite Interactions on Permeability of Clay-Rich Rocks Under CO2 Storage Conditions

CO2 uptake by smectites can cause swelling and self-stressing in shallow clay-rich caprocks under CO2 storage P–T and constrained conditions. However, little data exist to constrain the magnitude of the effects of CO2-H2O-smectite interactions on the sealing properties of clay-rich caprocks and faults. We performed permeability experiments on intact and fractured Opalinus Claystone (OPA) cores (~ 5% smectite), as well as on a simulated gouge-filled faults consisting of Na-SWy-1 montmorillonite, under radially constrained conditions simulating “open” transport pathways (dry and variably wet He or CO2; 10 MPa fluid pressure; 40 °C). Overall, the flow of dry CO2 through intact OPA samples and simulated smectite fault gouge caused a decrease in permeability by a factor of 4–9 or even by > 1 order, compared to dry He permeability. Subsequent to flow of dry and partially wet fluid, both fractured OPA and simulated gouge showed a permeability reduction of up to 3 orders of magnitude once flow-through with wet CO2 was performed. This permeability change appeared reversible upon re-establishing dry CO2 flow, suggesting fracture permeability was dominated by water uptake or loss from the smectite clay, with CO2-water-smectite interactions play a minor effect. Our results show that whether an increases or decreases in permeability of clayey caprock is expected with continuous flow of CO2-rich fluid depends on the initial water activity in the clay material versus the water activity in the CO2 bearing fluid. This has important implications for assessing the self-sealing potential of fractured and faulted clay-rich caprocks

Energy, resources & the environment: Current status

© 2014 The Authors. The EGU gathers geoscientists from Europe and the rest of the world, covering all disciplines of geosciences. Geoscientific interdisciplinarity is needed to tackle future challenges. A major challenge regards the provision of adequate and reliable supplies of affordable energy and resources obtained in environmentally sustainable ways, which are essential for economic prosperity, environmental quality and political stability around the world. One goal of the ERE division is to be a leading discussion forum for these subjects. The contributions in this issue present some of the challenges that were presented in the ERE division at the EGU General Assembly in 2014

Deformation behavior of sandstones from the seismogenic Groningen gas field : Role of inelastic versus elastic mechanisms

Reduction of pore fluid pressure in sandstone oil, gas, or geothermal reservoirs causes elastic and possibly inelastic compaction of the reservoir, which may lead to surface subsidence and induced seismicity. While elastic compaction is well described using poroelasticity, inelastic and especially time‐dependent compactions are poorly constrained, and the underlying microphysical mechanisms are insufficiently understood. To help bridge this gap, we performed conventional triaxial compression experiments on samples recovered from the Slochteren sandstone reservoir in the seismogenic Groningen gas field in the Netherlands. Successive stages of active loading and stress relaxation were employed to study the partitioning between elastic versus time‐independent and time‐dependent inelastic deformations upon simulated pore pressure depletion. The results showed that inelastic strain developed from the onset of compression in all samples tested, revealing a nonlinear strain hardening trend to total axial strains of 0.4 to 1.3%, of which 0.1 to 0.8% were inelastic. Inelastic strains increased with increasing initial porosity (12–25%) and decreasing strain rate (10−5 s−1 to 10−9 s−1). Our results imply a porosity and rate‐dependent yield envelope that expands with increasing inelastic strain from the onset of compression. Microstructural evidence indicates that inelastic compaction was controlled by a combination of intergranular cracking, intergranular slip, and intragranular/transgranular cracking with intragranular/transgranular cracking increasing in importance with increasing porosity. The results imply that during pore pressure reduction in the Groningen field, the assumption of a poroelastic reservoir response leads to underestimation of the change in the effective horizontal stress and overestimation of the energy available for seismicity

Impact of Chemical Environment on Compaction Creep of Quartz Sand and Possible Geomechanical Applications

Induced seismicity and surface subsidence are adverse effects of natural gas and geothermal energy production that may present barriers to their use as low-carbon alternatives to coal and oil. The driving force for these unwanted effects is compaction of the reservoir, which can potentially be mitigated by injecting (pressurized) fluids that restore the pore pressure and chemically inhibit compaction. We conducted uniaxial compaction experiments on quartz sand aggregates to investigate the effect of pore fluid chemistry on time-dependent compaction (creep). In addition to a low-vacuum (dry) environment, supercritical fluids (N2, CO2, and wet CO2), simple aqueous solutions (three HCl solutions and a NaOH solution), and complex aqueous solutions with additives (AlCl3, AMP, and washing detergent) were employed. N2, CO2, and fluids containing scaling inhibitor (AMP), as well as wastewater (detergent solution) are generally considered for injection. Compaction creep was enhanced in fluid-saturated environments compared to dry. Wet CO2 caused more creep with faster strain rates than the relatively dry CO2 and N2 environments. Experiments conducted with simple aqueous solutions exhibited a clear pH dependency. The complex aqueous solutions enhanced creep compared to their simple solution counterpart with similar pH. Based on acoustic emission data and microstructural analyses, we inferred that compaction creep was controlled by subcritical crack growth, aided by water, hydroxyl ions, and additives. If microcracking also controls compaction in reservoir sandstones, these results indicate that injection of supercritical fluids or acidic solutions may mitigate reservoir compaction