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Carbon sequestration in saline aquifers involves displacing brine from the pore space by supercritical CO(2) (scCO(2)). The displacement process is considered unstable due to the unfavorable viscosity ratio between the invading scCO(2) and the resident brine. The mechanisms that affect scCO(2)-water displacement under reservoir conditions (41 °C, 9 MPa) were investigated in a homogeneous micromodel. A large range of injection rates, expressed as the dimensionless capillary number (Ca), was studied in two sets of experiments: discontinuous-rate injection, where the micromodel was saturated with water before each injection rate was imposed, and continuous-rate injection, where the rate was increased after quasi-steady conditions were reached for a certain rate. For the discontinuous-rate experiments, capillary fingering and viscous fingering are the dominant mechanisms for low (logCa ≤ -6.61) and high injection rates (logCa ≥ -5.21), respectively. Crossover from capillary to viscous fingering was observed for logCa = -5.91 to -5.21, resulting in a large decrease in scCO(2) saturation. The discontinuous-rate experimental results confirmed the decrease in nonwetting fluid saturation during crossover from capillary to viscous fingering predicted by numerical simulations by Lenormand et al. (J. Fluid Mech.1988, 189, 165-187). Capillary fingering was the dominant mechanism for all injection rates in the continuous-rate experiment, resulting in monotonic increase in scCO(2) saturation.

a b s t r a c tCarbon dioxide enhanced oil recovery (CO 2 -EOR) and sequestration in depleted oil reservoirs is a plausible option for utilizing anthropogenic CO 2 to increase oil production while storing CO 2 underground. Evaluation of the storage resources and cost of potential CO 2 -EOR projects is an essential step before the commencement of large-scale deployment of such activities. In this paper, a hybrid techno-economic evaluation method, including a performance model and cost model for onshore CO 2 -EOR projects, has been developed based on previous studies. Total 296 onshore oil fields, accounting for about 70% of total mature onshore oil fields in China, were evaluated by the techno-economic method. The key findings of this study are summarized as follows:(1) deterministic analysis shows there are approximately 1.1 billion tons (7.7 billion barrels) of incremental crude oil and 2.2 billion tons CO 2 storage resource for onshore CO 2 -EOR at net positive revenue within the Chinese oil fields reviewed under the given operating strategy and economic assumptions. (2) Sensitivity study highlights that the cumulative oil production and cumulative CO 2 storage resource are very sensitive to crude oil price, CO 2 cost, project lifetime, discount rate and tax policy. High oil price, short project lifetime, low discount rate, low CO 2 cost, and low tax policy can greatly increase the net income of the oil enterprise, incremental oil recovery and CO 2 storage resource.(3) From this techno-economic evaluation, the major barriers to large-scale deployment of CO 2 -EOR include complex geological conditions, low API of crude oil, high tax policy, and lack of incentives for the CO 2 -EOR project.

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The MT2 receptor is a principal type of G protein-coupled receptor that mainly mediates the effects of melatonin. Deficits of melatonin/MT2 signaling have been found in many neurological disorders, including Alzheimer's disease, the most common cause of dementia in the elderly, suggesting that preservation of the MT2 receptor may be beneficial to these neurological disorders. However, direct evidence linking the MT2 receptor to cognition-related synaptic plasticity remains to be established. Here, we report that the MT2 receptor, but not the MT1 receptor, is essential for axonogenesis both in vitro and in vivo. We find that axon formation is retarded in MT2 receptor knockout mice, MT2-shRNA electroporated brain slices or primary neurons treated with an MT2 receptor selective antagonist. Activation of the MT2 receptor promotes axonogenesis that is associated with an enhancement in excitatory synaptic transmission in central neurons. The signaling components downstream of the MT2 receptor consist of the Akt/GSK-3β/CRMP-2 cascade. The MT2 receptor C-terminal motif binds to Akt directly. Either inhibition of the MT2 receptor or disruption of MT2 receptor-Akt binding reduces axonogenesis and synaptic transmission. Our data suggest that the MT2 receptor activates Akt/GSK-3β/CRMP-2 signaling and is necessary and sufficient to mediate functional axonogenesis and synaptic formation in central neurons. Synaptic circuits are established at the sites of axon-dendritic, axon-somatic or axon-axonal contact, in which functional axonogenesis is a critical step. 1 Axonogenesis can be regulated by many intracellular signals that involve cytoskeletal rearrangements, 2 local protein degradation, 3 as well as diffusional barriers. 4 Additionally, several extracellular neurotrophic factors and hormones have also been shown to have a role in axon guidance and synaptic formation in central neurons. 5,6 To date, the role of melatonin and its receptors in axonogenesis remains unclear. Most of the biological functions of melatonin are mediated by its two receptors, MT1 and MT2 receptors, both of them belong to the G protein-coupled receptor (GPCR) subfamily and are widely expressed throughout the central nervous system (CNS). 7 Activation of the MT2 receptor in response to melatonin is critical for controlling circadian rhythms 7 and regulation of slow wave sleep. 8,9 Early studies have shown that activation of the MT2 receptor in the retina reduces the release of dopamine, while dopamine inhibits growth cone motility and neurite outgrowth during embryonic development, 10,11 suggesting the involvement of the MT2 receptor in functional axonogenesis. In mutant mice with deficient expression of the MT2 gene, the induction of long-term potentiation (LTP) of excitatory synaptic transmission is impaired, and this impairment is closely related to deficits in learning. 12 In the hippocampus, the MT2 receptor inhibits GABA A receptor-mediated current, 13 which is implicated in the synaptic transmission. In Alzheimer's disease, expression of the MT...

The Liujiagou formation is an important CO 2 aquifer storage unit in the Ordos Basin in central China. Thus far, it has stored over 90% of the total injected CO 2 from the Shenhua carbon capture and storage (CCS) project, which is the fi rst full-chain CCS project in China. Understanding the basic properties of CO 2 fl ooding is critical for site characterization and evaluation. A core-scale characterization and CO 2 fl ooding study of Liujiagou sandstone is the fi rst step to understanding the fl ooding properties in a CO 2 aquifer storage project. The pore geometry of a sample was characterized using medical, industrial, and micro X-ray computed tomography (X-CT) scanners, as well as mercury intrusion porosity and thin section petrography. To study the fl ooding process, a CO 2 core fl ooding experiment using medical X-CT scanning was conducted with a Liujiagou sandstone sample. Based on the CT data, experimental data, simplifi ed models and COMSOL software, a three-dimensional sub-core scale numerical model that considered porosity, permeability, and capillary pressure heterogeneity was constructed for numerical simulation of CO 2 fl ooding under different scenarios. Laboratory experiments and numerical simulations on a Liujiagou sample revealed the following. The Liujiagou sandstone is a low-porosity and low-permeability sandstone with very high heterogeneity. The sub-core porosity heterogeneity signifi cantly affects CO 2 migration. The relative permeability and saturation distribution are signifi cantly affected by the injection velocity of CO 2 and are different from those of other sandstones, such as Berea. The analyzed Liujiagou sandstone sample has a very low storage effi ciency factor at the core scale. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifi cations or adaptations are made.Modeling and Analysis: CO 2 fl ooding properties of Liujiagou sandstone: infl uence of sub-core scale structure heterogeneity N Wei et al. 401

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