Aquifer thermal energy storage (ATES) is an underground thermal energy storage technology with a large potential to decarbonise the heating and cooling of buildings. ATES installations typically store thermal energy in aquifers that are also exploited for potable water, so a major consideration during development is ensuring that system operation will not lead to groundwater pollution. In this study, the risk of contamination due to upconing of a shallow freshwater/saltwater interface during ATES operation is investigated. Fluid flow, and heat and salt (chloride ion) transport are simulated in a homogeneous aquifer during ATES operation via a well doublet. The impact of geological, hydrological and operational parameters is investigated in a sensitivity analysis. Two new dimensionless numbers are proposed to characterise salt upconing and redistribution during ATES operation and provide a close match to simulated concentrations: CR,w characterises the contamination risk at the ATES installation, and CR,d characterises the risk at locations downstream of the ATES installation with respect to background groundwater flow. ATES systems with CR,w and CR,d < 10 introduce low risk of contamination in a homogenous aquifer, with chloride concentration at, and downstream of, the ATES system, remaining below the World Health Organisation’s advised limit. ATES installations with CR,w and CR,d > 10 cause a rapid increase in aquifer chloride concentration. The results are used to estimate an exclusion distance beyond which ATES system operation will not cause contamination in a homogenous aquifer. The dimensionless parameters proposed allow rapid assessment of the potential for saltwater contamination during ATES operation.
Understanding the stratigraphic fill and reconstructing the palaeo‐hydrology of incised valleys can help to constrain those factors that controlled their origin, evolution and regional significance. This condition is addressed through the analysis of a large (up to 18 km wide by 80 m deep) and exceptionally well‐imaged Late Pleistocene incised valley from the Sunda Shelf (South China Sea) based on shallow three‐dimensional seismic data from a large (11 500 km2), ‘merge’ survey, supplemented with site survey data (boreholes and seismic). This approach has enabled the characterization of the planform geometry, cross‐sectional area and internal stratigraphic architecture, which together allow reconstruction of the palaeo‐hydrology. The valley‐fill displays five notable stratigraphic features: (i) it is considerably larger than other seismically resolvable channel forms and can be traced for at least 180 km along its length; (ii) it is located in the axial part of the Malay Basin; (iii) the youngest part of the valley‐fill is dominated by a large (600 m wide and 23 m deep), high‐sinuosity channel, with well‐developed lateral accretion surfaces; (iv) the immediately adjacent interfluves contain much smaller, dendritic channel systems, which resemble tributaries that drained into the larger incised valley system; and (v) a ca 16 m thick, shell‐bearing, Holocene clay caps the valley‐fill. The dimension, basin location and palaeo‐hydrology of this incised valley leads to the conclusion that it represents the trunk river, which flowed along the length of the Malay Basin; it connected the Gulf of Thailand in the north with the South China Sea in the south‐east. The length of the river system (>1200 km long) enables examination of the upstream to downstream controls on the evolution of the incised valley, including sea‐level, climate and tectonics. The valley size, orientation and palaeo‐hydrology suggest close interaction between the regional tectonic framework, low‐angle shelf physiography and a humid‐tropical climatic setting. 相似文献
The integration of core sedimentology, seismic stratigraphy and seismic geomorphology has enabled interpretation of delta‐scale (i.e. tens of metres high) subaqueous clinoforms in the upper Jurassic Sognefjord Formation of the Troll Field. Mud‐prone subaqueous deltas characterized by a compound clinoform morphology and sandy delta‐scale subaqueous clinoforms are common in recent tide‐influenced, wave‐influenced and current‐influenced settings, but ancient examples are virtually unknown. The data presented help to fully comprehend the criteria for the recognition of other ancient delta‐scale subaqueous clinoforms, as well as refining the depositional model of the reservoir in the super‐giant Troll hydrocarbon field. Two 10 to 60 m thick, overall coarsening‐upward packages are distinguished in the lower Sognefjord Formation. Progressively higher energy, wave‐dominated or current‐dominated facies occur from the base to the top of each package. Each package corresponds to a set of seismically resolved, westerly dipping clinoforms, the bounding surfaces of which form the seismic ‘envelope’ of a clinoform set and the major marine flooding surfaces recognized in cores. The packages thicken westwards, until they reach a maximum where the clinoform ‘envelope’ rolls over to define a topset–foreset–toeset geometry. All clinoforms are consistently oriented sub‐parallel to the edge of the Horda Platform (N005–N030). In the eastern half of the field, individual foresets are relatively gently dipping (1° to 6°) and bound thin (10 to 30 m) clinothems. Core data indicate that these proximal clinothems are dominated by fine‐grained, hummocky cross‐stratified sandstones. Towards the west, clinoforms gradually become steeper (5° to 14°) and bound thicker (15 to 60 m) clinothems that comprise medium‐grained, cross‐bedded sandstones. Topsets are consistently well‐developed, except in the westernmost area. No seismic or sedimentological evidence of subaerial exposure is observed. Deposition created fully subaqueous, near‐linear clinoforms that prograded westwards across the Horda Platform. Subaqueous clinoforms were probably fed by a river outlet in the north‐east and sculpted by the action of currents sub‐parallel to the clinoform strike. 相似文献
A distinct magnetic cloud (MC) was observed in-situ at the Solar TErrestrial RElations Observatory (STEREO)-B on 20?–?21 January 2010. About three days earlier, on 17 January, a bright flare and coronal mass ejection (CME) were clearly observed by STEREO-B, which suggests that this was the progenitor of the MC. However, the in-situ speed of the event, several earlier weaker events, heliospheric imaging, and a longitude mismatch with the STEREO-B spacecraft made this interpretation unlikely. We searched for other possible solar eruptions that could have caused the MC and found a faint filament eruption and the associated CME on 14?–?15 January as the likely solar source event. We were able to confirm this source by using coronal imaging from the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)/EUVI and COR and Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronograph (LASCO) telescopes and heliospheric imaging from the Solar Mass Ejection Imager (SMEI) and the STEREO/Heliospheric Imager instruments. We use several empirical models to understand the three-dimensional geometry and propagation of the CME, analyze the in-situ characteristics of the associated ICME, and investigate the characteristics of the MC by comparing four independent flux-rope model fits with the launch observations and magnetic-field orientations. The geometry and orientations of the CME from the heliospheric-density reconstructions and the in-situ modeling are remarkably consistent. Lastly, this event demonstrates that a careful analysis of all aspects of the development and evolution of a CME is necessary to correctly identify the solar counterpart of an ICME/MC. 相似文献
The geomagnetic superstorm of 20 November 2003 with Dst=?422 nT, one of the most intense in history, is not well understood. The superstorm was caused by a moderate solar eruptive event on 18 November, comprehensively studied in our preceding Papers I?–?III. The analysis has shown a number of unusual and extremely complex features, which presumably led to the formation of an isolated right-handed magnetic-field configuration. Here we analyze the interplanetary disturbance responsible for the 20 November superstorm, compare some of its properties with the extreme 28?–?29 October event, and reveal a compact size of the magnetic cloud (MC) and its disconnection from the Sun. Most likely, the MC had a spheromak configuration and expanded in a narrow angle of ≤?14°. A very strong magnetic field in the MC up to 56 nT was due to the unusually weak expansion of the disconnected spheromak in an enhanced-density environment constituted by the tails of the preceding ICMEs. Additional circumstances favoring the superstorm were i) the exact impact of the spheromak on the Earth’s magnetosphere and ii) the almost exact southward orientation of the magnetic field, corresponding to the original orientation in its probable source region near the solar disk center. 相似文献