scholarly journals Marine electrical imaging reveals novel freshwater transport mechanism in Hawai‘i

2020 ◽  
Vol 6 (48) ◽  
pp. eabd4866
Author(s):  
Eric Attias ◽  
Donald Thomas ◽  
Dallas Sherman ◽  
Khaira Ismail ◽  
Steven Constable
Keyword(s):  
Transport Mechanism ◽  
High Elevation ◽  
Low Permeability ◽  
Fresh Groundwater ◽  
Aquifer Storage ◽  
Freshwater Transport ◽  
Electrical Imaging ◽  
Volcanic Islands ◽  
Water Saturated ◽  
Multilayer Formation

Conventional hydrogeologic framework models used to compute ocean island sustainable yields and aquifer storage neglect the complexity of the nearshore and offshore submarine environment. However, the onshore aquifer at the island of Hawai‘i exhibits a notable volumetric discrepancy between high-elevation freshwater recharge and coastal discharge. In this study, we present a novel transport mechanism of freshwater moving from onshore to offshore through a multilayer formation of water-saturated layered basalts with interbedded low-permeability layers of ash/soil. Marine electromagnetic imaging reveals ∼35 km of laterally continuous resistive layers that extend to at least 4 km from west of Hawai‘i’s coastline, containing about 3.5 km3 of freshened water. We propose that this newly found transport mechanism of fresh groundwater may be the governing mechanism in other volcanic islands. In such a scenario, volcanic islands worldwide can use these renewable offshore reservoirs, considered more resilient to climate change-driven droughts, as new water resources.

Delineation of Sedimentary Facies and Groundwater-Sea Water Disposition in an Intertidal Zone of the Bay of Bengal using GPR and VES

2018 ◽  
Vol 23 (2) ◽  
pp. 235-249
Author(s):  
Mrinal Kanti Layek ◽  
Palash Debnath ◽  
Probal Sengupta ◽  
Abhijit Mukherjee
Keyword(s):  
Bay Of Bengal ◽  
Sea Water ◽  
Water Saturation ◽  
Water Discharge ◽  
Ground Surface ◽  
Sedimentary Facies ◽  
Intertidal Flat ◽  
Sediment Layer ◽  
Fresh Groundwater ◽  
Water Saturated

A combination of geophysical study including ground penetrating radar (GPR) and vertical electrical sounding (VES) was done to identify different shallow-subsurface depositional features in an intertidal coast of the eastern parts of India, adjoining the Bay of Bengal (BoB) (Chandipur, Odisha state). The study was aimed to understand the variation of sedimentary depositional sequences, prograding to the ocean from land, as well as towards the confluence of a river channel with the BoB. Six VES points and 85 GPR traverses were taken in the intertidal flat. The data were calibrated with sedimentary sequences retrieved from simultaneously drilled boreholes in four locations. Resistivity data clearly demonstrate the subsurface sediment layer boundaries with water saturation variability, up to 156 m below ground surface (bgs). The data suggest thickening of brackish water saturated clay layers towards the southwestern part. GPR data were capable of resolving the geometry of intertidal dunes, buried palaeo-channels, erosional surface, water table, eolian deposit of sand, and washover delta depositional features which are all present in this study area. Several erosional surfaces, related to sedimentary processes, e.g., delta overwash processes, were clearly demarcated. The study also successfully identified and visualized the saline-fresh groundwater interfaces and submarine ground water discharge (SGD) zones. Consequently, based on these data, a conceptual model of the depositional and erosional history of the sedimentation of the area, as well as the coastal hydrogeological disposition, was conceived.

Borehole siting and construction in rural Malawi: A sociotechnical process?

Geophysics ◽  
2021 ◽  
pp. 1-38
Author(s):  
Timothy Larson ◽  
Zuze Dulanya ◽  
Evance Mwathunga
Keyword(s):  
Political Process ◽  
Technical Information ◽  
Saturated Sand ◽  
Resistivity Tomography ◽  
Aquifer Storage ◽  
Stakeholder Interests ◽  
Local Decision ◽  
Local Decision Making ◽  
Water Saturated ◽  
Competing Priorities

Choosing the site for a new water well in rural southern Malawi is essentially a political process with competing priorities and stakeholders. For a new well (or borehole) to be sustainably used and maintained, the relevant stakeholders must be fully engaged in the siting process and given meaningful responsibility for the final siting decision. However, without sound technical information, a siting decision based solely on stakeholder priorities such as proximity to the headman’s compound or accessibility to the center of population, may not result in a satisfactory borehole. Instead, in addition to stakeholder interests, we used a process that includes electrical resistivity tomography (ERT) as a tool to guide and constrain the local decision-making process. Within the region of the crystalline-basement aquifer, ERT profiles indicate variations in weathering thickness, hence aquifer storage. In a lacustrine setting, the ERT profile delineated a zone of moderately large resistivity associated with a deposit of fresh-water saturated sand. This ERT-derived technical information becomes one element in a comprehensive sociotechnical approach to the location of sustainable water resources. We used this sociotechnical approach to complete boreholes for all four villages in our project and have a high confidence that the villagers will be motivated to use and maintain these resources.

A Capillary Network Model for Coupled Gas and Water Flow in Engineered Barriers

1995 ◽  
Vol 412 ◽  
Author(s):  
M. D. Impy ◽  
P. Grindrod ◽  
K. J. Clark ◽  
H. Takase
Keyword(s):  
Network Model ◽  
Capillary Network ◽  
Low Permeability ◽  
Gas Migration ◽  
Capillary Bundle ◽  
Saturated Media ◽  
Engineered Barriers ◽  
Water Saturated ◽  
Preferential Pathways ◽  
Saturated Medium

AbstractA two-dimensional capillary network model for gas migration through a water-saturated medium is presented. The model is an extension of previously developed capillary bundle models, and provides a discrete alternative to classical continuum Darcy models. The need for such an alternative has become apparent from recent experimental results that suggest gas migrates through low permeability water-saturated media via a small number of preferential pathways.

Quantifying the Effect of Multiphase Flow on Matrix Acidizing in Oil-Bearing Carbonate Formations

2021 ◽  
pp. 1-12
Author(s):  
Mohamed Elsafih ◽  
Mashhad Fahes
Keyword(s):  
High Pressure ◽  
Multiphase Flow ◽  
Injection Rate ◽  
Low Permeability ◽  
Matrix Acidizing ◽  
Permeability Heterogeneity ◽  
Acid Injection ◽  
Water Saturated ◽  
Carbonate Formations ◽  
The Impact

Summary It is common to inject acidic stimulation fluids into oil-bearing carbonate formations to enhance well productivity. This process of matrix acidizing is designed to maximize the propagation of wormholes into the formation by optimizing the injection parameters, including acid-injection rate and volume. Previous studies have suggested that saturation conditions, permeability, heterogeneity, temperature, and pressure can significantly affect the design of matrix-acidizing treatments. However, laboratory studies’ results are inconsistent in their conclusions and are mostly limited to water-saturated cores. In this work, we designed a systematic experimental study to evaluate the impact of multiphase flow on the acidizing process when injecting 15 wt% hydrochloric acid (HCl) into crude-oil-saturated Indiana Limestone cores. The results reveal the following: Contrary to published literature for water-saturated cores, acidizing in partially oil-saturatedhigh-permeability cores at high pressure requires less acid volume than in low-permeability cores; lower-pressure acid injection results in more efficient wormhole propagation in low-permeability cores compared to high-pressure acid injection; acidizing in low- and high-permeability cores at low pressure leads to similar efficiency; and wormholing is more effective in partially oil-saturated cores, resulting in multiple parallel branches as compared to inefficient leakoff in water-saturatedcores.

Phát hiện nước ngọt dưới đất ngoài biển bằng phương pháp ảnh điện (ĐSĐ 2D)

2008 ◽  
Vol 30 (4) ◽  
pp. 374-377
Author(s):  
Nguyễn Hồng Bàng
Keyword(s):  
Imaging Method ◽  
Fresh Groundwater ◽  
Electrical Imaging

Detection of submarine fresh groundwater by electrical imaging method

Seismic study of the low-permeability volume in southern France karst systems

Geophysics ◽  
2014 ◽  
Vol 79 (1) ◽  
pp. EN1-EN13 ◽  
Author(s):  
Pierre-Yves Galibert ◽  
Rémi Valois ◽  
Manuela Mendes ◽  
Roger Guérin
Keyword(s):  
Seismic Attenuation ◽  
Low Permeability ◽  
Driving Mechanism ◽  
Refraction Tomography ◽  
Seismic Amplitudes ◽  
Karst Systems ◽  
Water Saturated ◽  
Low Amplitude ◽  
Wave Induced

Locating groundwater in deep-seated karst aquifers is inherently difficult. With seismic methods, we studied the upper epikarst and the underneath low-permeability volume (LPV) of several karst systems located in the southern Quercy and Larzac regions of France and found that refraction tomography was effective only in the epikarst and not in the LPV. We evaluated a 3D case study using a combination of surface records and downhole receivers to overcome this limitation. This 3D approach unveiled a set of elongated furrows at the base of the epikarst and identified heterogeneities deep inside the LPV that may represent high-permeability preferred pathways for water inside the karst. To achieve the same result when no borehole was available, we studied seismic amplitudes of the wavefield, recognizing that wave-induced fluid flow in low-permeability carbonates is a driving mechanism of seismic attenuation. We developed a workflow describing the heterogeneity of the LPV with spectral attributes derived from surface-consistent decomposition principles, and we validated its effectiveness at benchmark locations. We applied this workflow to the 3D study and found a low-amplitude signal area at depth; we interpreted this anomaly as a water-saturated body perched above the aquifer.

scholarly journals INFLUENCE OF INCLINATION ANGLE OF THE BOREHOLE AXIS ON THEPOSSIBLE MANIFESTATIONS OF RESERVOIR WATER

2018 ◽  
pp. 54-59
Author(s):  
V. P. Ovchinnikov ◽  
D. S. Gerasimov ◽  
F. A. Agzamov ◽  
P. V. Ovchinnikov ◽  
V. V. Saltykov ◽  
...  
Keyword(s):  
Inclination Angle ◽  
Oil And Gas ◽  
Low Permeability ◽  
Clay Layer ◽  
Gas Reservoirs ◽  
Reservoir Water ◽  
Inclination Angles ◽  
Oil And Gas Reservoirs ◽  
Water Saturated

Secondary opening of productive oil and gas reservoirs by using cumulative and bullet perfo-ration methods in directional wells with high values of inclination angles (40-60º) requires a solution of technological problems caused by the justification of the interval of their implementation. This is especially important for multi-layered reservoirs with alternating water saturated and oil saturated horizons and the absence of an insulating low-permeability screen, for example, a clay layer (tire). The article makes an attempt to attract geological services, owners of companies that develop deposits with such conditions, in order to increase the requirements for the appointment of a perforation interval. The authors give some proposals based on the actual results of well con-struction.

Capillary entry pressure and the leakage of gravity currents through a sloping layered permeable rock

2009 ◽  
Vol 618 ◽  
pp. 361-379 ◽  
Author(s):  
ANDREW W. WOODS ◽  
ADRIAN FARCAS
Keyword(s):  
Saline Aquifers ◽  
Permeability Barrier ◽  
Low Permeability ◽  
Porous Rock ◽  
Entry Pressure ◽  
Permeable Rock ◽  
Lateral Extent ◽  
Water Saturated ◽  
Capillary Entry Pressure ◽  
Instantaneous Release

We examine the motion of a buoyant fluid injected into a water-saturated porous rock as it spreads along a thin inclined low-permeability barrier. We account for leakage of the fluid across the barrier once the current is sufficiently deep so that the pressure exceeds the capillary threshold. We show that at some distance from the source, the pressure decreases below this threshold, and all the remaining flux spreads laterally along the barrier. We examine the controls on the partitioning of the flow between the draining flux and the laterally spreading flux and also the controls on the lateral extent of the draining region for the case of an instantaneous release and a maintained release of fluid. We consider the implications of our work for the dispersal of CO2 plumes which may be sequestered in deep saline aquifers.

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