How do permeable fractures in the Triassic sediments of Northern Alsace characterize the top of hydrothermal convective cells? Evidence from Soultz geothermal boreholes (France)

Vidal, Jeanne; Genter, Albert; Schmittbuhl, Jean

doi:10.1186/s40517-015-0026-4

Cited by 36 publications

(37 citation statements)

References 19 publications

(32 reference statements)

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“…Normally, the ROP decreases as the drill bit bores into denser formations (Vidal et al 2015). Raw ROP values are clearly dependent of WOB (weight on bit), RPM (rotation), bit size or mud composition (bulk density).…”

Section: Terminologymentioning

confidence: 99%

“…In addition, loss of the entire whole drilling fluid (mud) indicates that the well has intersected a permeable fracture zone. In the Soultz wells, it has been observed during drilling operations that all the mud losses were clearly related to natural fracture zones both in sediments and in granite (Vidal et al 2015;Genter 1999). Porosity values were quite low even in the sediments.…”

Section: Terminologymentioning

confidence: 99%

“…In addition to the stratigraphic contribution, a structural analysis of the main fracture zones intersecting the sedimentary part of the Soultz-sous-Forêts wells is proposed. This structural analysis is based on different scales: large scale with the seismic profile (Cautru 1988 redrawn by Koelbel et al 2011), 2D visualization with the well-to-well correlations and 1D with borehole data (mud logging, well logs) (Vidal et al 2015). The goal of this analysis is to interpret the thickness variations of the stratigraphic units to identify the zones affected by faults with the help of other data (seismic profile and mud logging).…”

Section: Major Oilfields Geothermal Gradientsmentioning

confidence: 99%

“…Faults will also be used for the description of the seismic profile because a profile is supposed to represent only large "faults" with minimum vertical apparent offset of 10 m (Walsh 1988). Natural fracture or fault permeability is mainly based on mud losses, gas anomalies (Helium, CO 2 ) and high ROP values recorded during drilling operations (Vuataz et al 1990;Vidal et al 2015). In addition, temperature logs as well as spinner logs combined with acoustic log (BHTV) are a very powerful tool for identifying fractures bearing natural permeability in a Soultz borehole (Evans et al 2005).…”

Section: Terminologymentioning

confidence: 99%

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New stratigraphic interpretation of the Soultz-sous-Forêts 30-year-old geothermal wells calibrated on the recent one from Rittershoffen (Upper Rhine Graben, France)

Aichholzer

Duringer

Orciani³

et al. 2016

Geotherm Energy

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The Soultz-sous-Forêts site (Alsace, France) is the first pilot geothermal project in the world that furnished the proof of concept of enhanced geothermal systems by producing energy from a deep-seated granite. The Alsace region, with its hundreds of previous drillings and seismic history related to both oil and potash exploitation, has been shown to have high subterranean temperatures. In the Soultz-sous-Forêts geothermal project, most attention has focused on the basement and the sedimentary cover/basement interface. Thus, the sedimentary portion of the well (approximately 1.4 km thick) has never been fully investigated. The only available data on the Soultzsous-Forêts sedimentary cover are from an old masterlog (GPK-1) with interpretations of the tops and bases of the main geological formations, and from some other less well-documented well logs (EPS-1 and GPK-2). The main challenge of this work is therefore to re-interpret the old well data to provide precise and detailed chronolithostratigraphic logs for GPK-1 and GPK-2, especially in their sedimentary portions. These new investigations of the GPK wells have been possible due to the new data collected in the recent geothermal wells at Rittershoffen (GRT-1 and GRT-2, located 6.5 km from Soultz-sous-Forêts), which are characterized by a quite complete stratigraphic succession. Both sites have been explored by deep drilling operations aiming to exploit the heat extracted from a deep granitic basement (Palaeozoic) covered by a stack of 1.4-and 2.2-km-thick sedimentary rocks (Mesozoic to Cenozoic) at Soultz-sous-Forêts and Rittershoffen, respectively. Thus, the Rittershoffen chrono-lithostratigraphic logs have been used as a baseline to interpret the sedimentary succession in GPK-1 and GPK-2. In conclusion, all the well logs are compared for stratigraphic comparisons. With approximately 1400 m of sedimentary cover at Soultz-sous-Forêts instead of 2200 m at Rittershoffen, the correlation between the two sites showed many differences exist in the sedimentary columns: layers missing due to erosion, lateral thickness variations in formations, and-above all-the occurrence of at least four major fracture zones affecting the units. In addition, a structural analysis was made to more precisely define the limits of the geological formations observed and to present more arguments for the presence of fracture zones or faults.

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Section: Terminologymentioning

confidence: 99%

Section: Terminologymentioning

confidence: 99%

Section: Major Oilfields Geothermal Gradientsmentioning

confidence: 99%

Section: Terminologymentioning

confidence: 99%

See 2 more Smart Citations

New stratigraphic interpretation of the Soultz-sous-Forêts 30-year-old geothermal wells calibrated on the recent one from Rittershoffen (Upper Rhine Graben, France)

Aichholzer

Duringer

Orciani³

et al. 2016

Geotherm Energy

View full text Add to dashboard Cite

show abstract

“…3). Such a structural framework induces a hydrothermal convection up to the base of the evaporites of the Keuper formation, which constitute a cap-rock for the convection (Vidal et al 2015;Maurer et al 2018).…”

mentioning

confidence: 99%