Onset of Fault-Bounded Free Thermal Convection in a Fluid-Saturated Horizontal Permeable Porous Layer

Malkovsky, V. I.; Pék, A. A.

doi:10.1007/s11242-015-0555-0

Cited by 14 publications

(10 citation statements)

References 23 publications

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“…This dependence of interfault fluid circulation on fault spacing is consistent with the theoretical analysis of conditions for the onset of free thermal convection in a fault‐bounded convection cell (Malkovsky & Pek ). Optimal conditions for fault‐bounded convection were estimated to be at a fault spacing equal to approximately 0.6–0.8 times the vertical length.…”

Section: Numerical Simulation Resultssupporting

confidence: 87%

“…The theoretical problem of the onset of fault‐bounded thermal convection in a fluid‐saturated horizontal porous layer was considered in Malkovsky & Pek (). The results obtained, briefly reviewed in the next section, are in reasonable agreement with the concept of fault‐bounded convection cells as an explanation for fluid upflow and downflow via basement fault zones.…”

Section: Introductionmentioning

confidence: 99%

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Linked thermal convection of the basement and basinal fluids in formation of the unconformity‐related uranium deposits in the Athabasca Basin, Saskatchewan, Canada

Pék

Malkovsky

2016

Geofluids

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World‐class unconformity‐related U deposits in the Athabasca Basin (Saskatchewan, Canada) are generally located within or near fault zones that intersect the unconformity between the Athabasca Group sedimentary basin rocks and underlying metamorphic basement rocks. Two distinct subtypes of unconformity‐related uranium deposits have been identified: those hosted primarily in the Athabasca Group sandstones (sediment‐hosted) and those hosted primarily in the underlying basement rocks (basement‐hosted). Although significant research on these deposits has been carried out, certain aspects of their formation are still under discussion, one of the main issues being the fluid flow mechanisms responsible for uranium mineralization. The intriguing feature of this problem is that sediment‐hosted and basement‐hosted deposits are characterized by oppositely directed vectors of fluid flow via associated fault zones. Sediment‐hosted deposits formed via upward flow of basement fluids, basement‐hosted deposits via downward flow of basinal fluids. We have hypothesized that such flow patterns are indicative of the fluid flow self‐organization in fault‐bounded thermal convection (Transport in Porous Media, 110, 2015, 25). To explore this hypothesis, we constructed a simplified hydrogeologic model with fault‐bounded thermal convection of fluids in the faulted basement linked with fluid circulation in the overlying fault‐free sandstone horizon. Based on this model, a series of numerical experiments was carried out to simulate the hypothesized fluid flow patterns. The results obtained are in reasonable agreement with the concept of fault‐bounded convection cells as an explanation of focused upflow and downflow across the basement/sandstone unconformity. We then discuss application of the model to another debated problem, the uranium source for the ore‐forming basinal brines.

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Section: Numerical Simulation Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Linked thermal convection of the basement and basinal fluids in formation of the unconformity‐related uranium deposits in the Athabasca Basin, Saskatchewan, Canada

Pék

Malkovsky

2016

Geofluids

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“…; Kühn et al . ; Malkovsky & Pek ). For example, Simms & Garven () demonstrated that in a faulted rift basin, model geometry, including faults and boundaries, can control convection cell spacing and structure.…”

Section: Introductionmentioning

confidence: 98%

“…For example, Simms & Garven () demonstrated that in a faulted rift basin, model geometry, including faults and boundaries, can control convection cell spacing and structure. Malkovsky & Pek () further showed that high fault zone permeability and hydrostatic fluid pressure favour the development of the fault‐bounded convective flow in homogeneous permeable rocks. For the Athabasca Basin, it has been proposed that convective fluid flow driven by a thermal gradient may have developed in the high‐permeability basinal sequence at the basin scale (Raffensperger & Garven ) and that large‐scale free thermal convection may be responsible for uranium uptake and transport (Hoeve & Quirt ; Kyser & Cuney ).…”

Section: Introductionmentioning

confidence: 99%

The effects of basement faults on thermal convection and implications for the formation of unconformity‐related uranium deposits in the Athabasca Basin, Canada

Chi

Bethune

2016

Geofluids

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The formation of the world‐class, high‐grade unconformity‐related uranium deposits in the Athabasca Basin (Canada) requires circulation of large amounts of fluids, the mechanisms for which are still not well understood. Recent studies advocate thermal convection as a possible driving force for the fluid flow related to uranium mineralization; however, little is known regarding how basement faults, which are spatially associated with most unconformity‐related uranium deposits, influence fluid convection and how this may affect the localization of mineralization. This study addresses these questions through simulations of thermal convection with various configurations of basement faults using the FLAC3D software. Modelling results indicate that the location, spacing, orientation and thermal conductivities of basement faults influence the size and location of thermally driven fluid convection. In a model with a single isolated fault, the fault coincides with an upwelling plume and the dip angle of the fault does not affect the fluid flow pattern; when the fault is moved laterally, the upwelling plume shifts accordingly. In the case of two vertical faults, the faults may either coincide with upwelling flow between two convection cells or be located below individual convection cells, depending on fault spacing. In the latter case, fluid may flow into and out of individual fault zones. Similar results were also obtained for models with two nonvertical (i.e. dipping) faults. Convective flow can penetrate the uppermost basement when the permeability is less than two orders of magnitude lower than that of the overlying sandstone. In this case, the basement faults not only can control the location of ascending flow, but also can passively act as fluid conduits of either flow from the basin into the basement (ingress), or flow from the basement into the basin (egress), depending on their thermal conductivities and relative locations in the models.

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“…Le Carlier et al, 1994;Simms & Garven, 2004). Malkovsky and Pek (2015) investigated convection in two faults separated by a permeable host, showing that fault spacing is a primary control on whether convection forms individually in each fracture (intrafracture) or a single, connected cell forms in both (interfracture). Malkovsky and Pek (2015) investigated convection in two faults separated by a permeable host, showing that fault spacing is a primary control on whether convection forms individually in each fracture (intrafracture) or a single, connected cell forms in both (interfracture).…”

Section: Introductionmentioning

confidence: 99%

Self‐Organizing Fluid Convection Patterns in an en Echelon Fault Array

Patterson¹,

Driesner²,

Matthäi

2018

Geophysical Research Letters

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We present three‐dimensional numerical simulations of natural convection in buried, vertical en echelon faults in impermeable host rock. Despite the fractures being hydraulically disconnected, convection within each fracture alters the temperature field in the surrounding host rock, altering convection in neighboring fractures. This leads to self‐organization of coherent patterns of upward/downward flow and heating/cooling of the host rock spanning the entire fault array. This “synchronization” effect occurs when fracture spacing is less than the width of convection cells within the fractures, which is controlled by fracture transmissivity (permeability times thickness) and heterogeneity. Narrow fracture spacing and synchronization enhance convective fluid flow within fractures and cause convection to initiate earlier, even lowering the critical transmissivity necessary for convection initiation. Heat flow through the en echelon region, however, is enhanced only in low‐transmissivity fractures, while heat flow in high‐permeability fractures is reduced due to thermal interference between fractures.

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Onset of Fault-Bounded Free Thermal Convection in a Fluid-Saturated Horizontal Permeable Porous Layer

Cited by 14 publications

References 23 publications

Linked thermal convection of the basement and basinal fluids in formation of the unconformity‐related uranium deposits in the Athabasca Basin, Saskatchewan, Canada

Linked thermal convection of the basement and basinal fluids in formation of the unconformity‐related uranium deposits in the Athabasca Basin, Saskatchewan, Canada

The effects of basement faults on thermal convection and implications for the formation of unconformity‐related uranium deposits in the Athabasca Basin, Canada

Self‐Organizing Fluid Convection Patterns in an en Echelon Fault Array

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