Integrated Use of Geological, Geophysical, Radiocarbon and Stable Isotopes Data for Tracing the Conduit Flow Paths in a Small Karstic Aquifer: Poocher Swamp Freshwater Lens, South Australia

An integrated approach combining lithological logs, downhole geophysics, electromagnetic survey and the distribution of radiocarbon (14C) and the stable isotopes of water molecules (18O) were used to identify the conduit flow paths of a small freshwater lens. Lost circulation zones, where drilling fluid flows into geological formation instead returning up the annulus recorded during water well drilling, were considered as the major fracture zones. The presence of high porosity zones within boreholes were identified using caliper, gamma and neutron logs. These methods were used to identify the depth intervals at which cavities and the existence of conduit porosity within the boreholes. Transient electromagnetic (TEM) method was used to investigate resistivity anomalies in the profiles along nine pre-determined lines across the freshwater lens. Resistivity anomalies were related to borehole information and other surface features such as sinkholes. Low resistivity zones of the TEM tomography sections had excellent correlation to fracture zones identified during well drilling, and downhole geophysical logs. Similarly, high resistivity zones in the profiles correlate well with the zones of cemented or recrystallized limestone identified from the lithological logs. The interpreted resistivity anomaly accurately depicts depth to watertable at 15-18 m, presence of main fracture zone at 20-25 m, presence of possible conduits flow paths and the cemented or recrystallized limestone below 35 m depth. The 14C, 13C and 18O signatures of the groundwater confirm the presence of conduits and potential pathways of preferential flows. This investigation illustrates the effectiveness using an integrated approach to trace the conduit flow paths in karst aquifers. The information gained from the study is currently being used for the management of the freshwater lens.

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Diffuse Versus Conduit Flow in Coastal Karst Aquifers: The Consequences of Island Area and Perimeter Relationships

Geosciences ◽

10.3390/geosciences8070268 ◽

2018 ◽

Vol 8 (7) ◽

pp. 268 ◽

Cited By ~ 3

Author(s):

Erik Larson ◽

John Mylroie

Keyword(s):

Discharge Zone ◽

Flow Transition ◽

High Porosity ◽

Freshwater Lens ◽

Conduit Flow ◽

Diffuse Flow ◽

Porosity And Permeability ◽

Area And Perimeter ◽

Bahamian Archipelago ◽

Flank Margin Caves

The majority of limestone islands are made of eogenetic carbonate rock, with intrinsic high porosity and permeability. The freshwater lenses of small islands are dominated by diffuse flow regimes as the island perimeter is everywhere close to the meteoric catchment of the island interior. This flow regime produces flank margin caves at the lens margin, where dissolution is enhanced by mixing corrosion, superposition of organic decay horizons and higher flow velocities as the lens thins. The lens interior develops touching-vug flow systems that result in enhanced permeability and lens thinning over time. As islands become larger, the area (meteoric catchment) goes up by the square, but the island perimeter (discharge zone) goes up linearly; diffuse flow becomes inefficient; conduit flow develops to produce traditional epigenic cave systems that discharge the freshwater lens by specific turbulent flow routes, which in turn are fed by diffuse flow in the island interior. Locally, diffuse flow to the island perimeter continues in coastal proximal areas between major conduit flow routes to produce flank margin caves. The Bahamian Archipelago represents a case history in which tectonics is limited, the rocks are entirely eogenetic and the diffuse to conduit flow transition is demonstrated.

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Investigation of Groundwater In-rush Zone using Petrophysical Logs and Short-offset Transient Electromagnetic (SOTEM) Data

Journal of Environmental and Engineering Geophysics ◽

10.32389/jeeg18-111 ◽

2020 ◽

Vol 25 (3) ◽

pp. 433-437

Author(s):

Muhammad Younis Khan ◽

Guo-Qiang Xue ◽

Wei-Ying Chen ◽

Cyril D. Boateng

Keyword(s):

Gamma Ray ◽

Water Inrush ◽

Northern China ◽

Integrated Approach ◽

High Resistivity ◽

Coal Seams ◽

Transient Electromagnetic ◽

Resistivity Logs ◽

Petrophysical Logs ◽

Occam Inversion

The water burst from the Ordovician limestone underlain by the Permo-Carboniferous coal seams have potential to trigger coalmine hazards in Northern China. Therefore, it is crucial to identify and accurately map the water enrichment zones and delineate coal seams using an integrated approach based on surface TEM and subsurface wireline log information to avoid water-inrush hazard and ensure safe production of coal. We inverted surface based TEM data using 1-D Occam inversion to identify the conductive anomaly and then further quantified the zone of interest by gamma and resistivity logs. 1-D Occam inversion results show conductive zone around 370 m while higher resistivity and lower gamma ray log signatures were observed against coal seams. Groundwater inrush zone falls within the mid-range gamma ray and resistivity interval as shown on the petrophysical logs. The distinct log signatures (low gamma-ray and high resistivity values) clearly indicated coal seams at depth of 410 and 470 m and subsequently the log trends were used to distinguish between coal units and more permeable sands. The magnitude and the variability of these parameters in the borehole are attributed to the subsurface stratigraphic heterogeneity. They can be key clues for interpretation of depositional facies of coal-bearing sequence and may also be used as a constraint in characterization of groundwater enrichment zone.

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Depth–Sequential Investigation of Major Ions, δ18o, δ2h and δ13C in Fractured Aquifers of the St. Lawrence Lowlands (Quebec, Canada) Using Passive Samplers

Water ◽

10.3390/w13131806 ◽

2021 ◽

Vol 13 (13) ◽

pp. 1806

Author(s):

Guillaume Meyzonnat ◽

Florent Barbecot ◽

José Corcho Alvarado ◽

Daniele Luigi Pinti ◽

Jean-Marc Lauzon ◽

...

Keyword(s):

Stable Isotopes ◽

Major Ions ◽

Anthropogenic Activities ◽

Carbon Sources ◽

Passive Samplers ◽

Flow Paths ◽

Aquifer Heterogeneity ◽

Fractured Aquifers ◽

Fractured Carbonate ◽

Observation Wells

General and isotopic geochemistry of groundwater is an essential tool to decipher hydrogeological contexts and flow paths. Different hydrogeochemical patterns may result from the inherent physical aquifer heterogeneity, which may go unnoticed without detailed investigations gathered from multilevel or multiple observation wells. An alternative to overcome the frequent unavailability of multiple wellbores at sites is to perform a detailed investigation on the single wellbore available. In this perspective, the aim of this study is to use passive samplers to sequentially collect groundwater at depths in long–screened wellbores. Such investigation is carried out for major ions and stable isotopes compositions (δ2H, δ18O, δ13C) at ten sites in the context of fractured carbonate aquifers of the St. Lawrence Lowlands (Quebec, Canada). The information gathered from the calco–carbonic system, major ions and stable isotopes report poorly stratified and evolved groundwater bodies. Contribution of water impacted by anthropogenic activities, such as road salts pollution and carbon sources from C4 vegetation, when they occur, are even observed at the greatest depths. Such observations suggest quick flow paths and efficient mixing conditions, which leads to significant contributions of contemporary groundwater bodies in the fractured aquifers investigated down to depths of about 100 m. Although physical aquifer investigation reported few and heterogeneously distributed fractures per wellbore, hydrogeochemical findings point to at overall well interconnected fracture networks in the aquifer and high vulnerability of groundwater, even at significant depths.

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Integrated approach for the U-type horizontal well drilling & geosteering in shallow Turonian sands

10.3997/2214-4609.202131040 ◽

2021 ◽

Author(s):

A. Valiakhmetov ◽

V. Kramar ◽

R. Khabibullin ◽

I. Shmarin ◽

V. Vorobev ◽

...

Keyword(s):

Horizontal Well ◽

Integrated Approach ◽

Well Drilling

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Integrated Analysis of Tracer and Pressure-Interference Tests To Identify Well Interference

SPE Journal ◽

10.2118/201233-pa ◽

2020 ◽

Vol 25 (04) ◽

pp. 1623-1635 ◽

Cited By ~ 1

Author(s):

Ashish Kumar ◽

Puneet Seth ◽

Kaustubh Shrivastava ◽

Ripudaman Manchanda ◽

Mukul M. Sharma

Keyword(s):

Response Times ◽

Horizontal Wells ◽

Integrated Approach ◽

Pressure Response ◽

Integrated Analysis ◽

Well Drilling ◽

Tracer Recovery ◽

Well Spacing ◽

Fractured Horizontal Wells ◽

Interference Tests

Summary In ultralow-permeability reservoirs, communication between wells through connected fractures can be observed through tracer and pressure-interference tests. Understanding the connectivity between fractured horizontal wells in a multiwell pad is important for infill well drilling and parent-child well interactions. Interwell tracer and pressure-interference tests involve two or more fractured horizontal wells and provide information about hydraulic-fracture connectivity between the wells. In this work, we present an integrated approach based on the analysis of tracer and pressure interference data to obtain the degree of interference between fractured horizontal wells in a multiwell pad. We analyze well interference using tracer (chemical tracer and radioactive proppant tracer) and pressure data in an 11-well pad in the Permian Basin. Changes in pressure and tracer concentration in the monitor wells were used to identify and evaluate interference between the source and monitor wells. Extremely low tracer recovery and weak pressure response signify the absence of connected fractures and suggest that interference through matrix alone is insignificant. Combined tracer and pressure-interference data suggest connected fracture pathways between the communicating wells. The degree of interference can be estimated in terms of pressure response times and tracer recovery. An effective reservoir model was used to simulate pressure interference between wells during production. Simulation results indicate that well interference observed during production is primarily because of hydraulically connected fractures. Combined tracer and pressure-interference analysis provides a unique tool for understanding the time-dependent connectivity between communicating wells, which can be useful for optimizing infill well drilling, well spacing, and fracture sizing in future treatment designs.

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Characterisation of subglacial water using a constrained transdimensional Bayesian transient electromagnetic inversion

Solid Earth ◽

10.5194/se-11-75-2020 ◽

2020 ◽

Vol 11 (1) ◽

pp. 75-94 ◽

Cited By ~ 1

Author(s):

Siobhan F. Killingbeck ◽

Adam D. Booth ◽

Philip W. Livermore ◽

C. Richard Bates ◽

Landis J. West

Keyword(s):

Electrical Resistivity ◽

Saline Water ◽

Radar Data ◽

High Resistivity ◽

Transient Time ◽

Fractured Bedrock ◽

Transient Electromagnetic ◽

Seismic Shear ◽

Time Domain Electromagnetic ◽

Ground Penetrating

Abstract. Subglacial water modulates glacier-bed friction and therefore is of fundamental importance when characterising the dynamics of ice masses. The state of subglacial pore water, whether liquid or frozen, is associated with differences in electrical resistivity that span several orders of magnitude; hence, liquid water can be inferred from electrical resistivity depth profiles. Such profiles can be obtained from inversions of transient (time-domain) electromagnetic (TEM) soundings, but these are often non-unique. Here, we adapt an existing Bayesian transdimensional algorithm (Multimodal Layered Transdimensional Inversion – MuLTI) to the inversion of TEM data using independent depth constraints to provide statistical properties and uncertainty analysis of the resistivity profile with depth. The method was applied to ground-based TEM data acquired on the terminus of the Norwegian glacier, Midtdalsbreen, with depth constraints provided by co-located ground-penetrating radar data. Our inversion shows that the glacier bed is directly underlain by material of resistivity 102 Ωm ± 1000 %, with thickness 5–40 m, in turn underlain by a highly conductive basement (100 Ωm ± 15 %). High-resistivity material, 5×104 Ωm ± 25 %, exists at the front of the glacier. All uncertainties are defined by the interquartile range of the posterior resistivity distribution. Combining these resistivity profiles with those from co-located seismic shear-wave velocity inversions to further reduce ambiguity in the hydrogeological interpretation of the subsurface, we propose a new 3-D interpretation in which the Midtdalsbreen subglacial material is partitioned into partially frozen sediment, frozen sediment/permafrost and weathered/fractured bedrock with saline water.

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Identification of Double-layered Water-filled Zones Using TEM: A Case Study in China

Journal of Environmental and Engineering Geophysics ◽

10.2113/jeeg23.3.297 ◽

2018 ◽

Vol 23 (3) ◽

pp. 297-304

Author(s):

Guoqiang Xue ◽

Dongyang Hou ◽

Weizhong Qiu

Keyword(s):

Field Survey ◽

Coal Mines ◽

Northern China ◽

Shanxi Province ◽

Well Drilling ◽

Borehole Logging ◽

Transient Electromagnetic ◽

Geophysical Technique ◽

Instrument Sensitivity

At present in China, the use of the transient electromagnetic method (TEM) is emerging as a leading geophysical technique for exploration of water-filled zones in coal mines. These zones are more conductive than the host coal and are easy targets to map. However, there is a growing interest for the investigations of double-layered or multi-layered mined-out zones. Therefore, it is necessary to study the feasibility of TEM's abilities to detect double-layered, water-filled voids. In this study, the basic hydrogeological conditions of a survey area, located in the northern China, are described. The corresponding geophysical models of the single- and double-layered water-filled zones are developed from borehole logging data. Then, forward calculations of different models are carried out with 1D numerical simulations. The modeling results show that it is feasible for TEM to identify these types of targets under certain conditions, including instrument sensitivity, low resistivity for the water-filled zones, and shallower depths. Moreover, the field survey for locating double-layered water-filled zones in coal mines in the Datong region of Shanxi Province is verified by well drilling.

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