A new stereographic technique for the reduction of scanline survey data of geologic fractures

Lacazette, Alfred

doi:10.1016/0098-3004(91)90051-e

Cited by 17 publications

(8 citation statements)

References 5 publications

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“…A total of nine scanline surveys were conducted along the quarry walls. Strike, dip and distance along the scanline were recorded for all fractures that intersected the tape measure, and stereographic plots showing fracture frequency as a function of orientation were constructed using the computer program developed by Lacazette [ 1991]. Scanlines 1-5 were conducted in the western sector,, and scanlines 6-9 were measured in the eastern sector.…”

Section: Scanline Surveys In the Gasport Quarrymentioning

confidence: 99%

A case for neotectonic joints along the Niagara Escarpment

Gross¹,

Engelder²

1991

Tectonics

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In a search for proof that some joints on the Appalachian Plateau are neotectonic, orientation data were collected on more than 1800 fractures in exposures of the Lockport Dolomite in western New York and southern Ontario. Of greatest interest was a late-forming ENE joint set present in the central and western portions of the field area. These joints increase in abundance with proximity to the Niagara Escarpment. The shape of the east-west trending Niagara Escarpment is defined by a series of asymmetric reentrants with a strong ENE linear trend, reflecting the bedrock joint pattern. The joints appear to have formed near the Earth's surface in response to low tensile stresses developed in bedrock adjacent to the retreating escarpment. Since the current shape and position of the escarpment were controlled by glacial activity during the last 3 m.y., it is possible that the ENE joints and reentrants are neotectonic features. J" 70 o I-oo •. so 0 ß ß ß ß ß ß ß ß RE-ENTRANTS LONGITUDE (o)

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Section: Scanline Surveys In the Gasport Quarrymentioning

confidence: 99%

A case for neotectonic joints along the Niagara Escarpment

Gross¹,

Engelder²

1991

Tectonics

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“…The approach we have chosen to use, the scanline survey method described by Priest and Hudson (1981), is a widely accepted method for the characterization of discontinuity networks (e.g. La Pointe and Hudson, 1985;Lacazette, 1991;Narr, 1996). The advantages of the method are especially the acquisition time and the associated verification as well as the acquisition costs compared to other methods (e.g.…”

Section: Estimating the Geological Subsurface Model Of The Carbonate Reservoirmentioning

confidence: 99%

Characterization of discontinuities in potential reservoir rocks for geothermal applications in the Rhine-Ruhr metropolitan area (Germany)

et al. 2021

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Abstract. The importance of research into clean and renewable energy solutions has increased over the last decade. Geothermal energy provision is proven to meet both conditions. Therefore, conceptual models for deep geothermal applications were developed for different field sites regarding different local conditions. In Bavaria, Germany, geothermal applications were successfully carried out in carbonate horizons at depths of 4000 to 6000 m. Matrix permeability and thermal conductivity was mainly studied in karstified carbonates from the Late Jurassic reef facies. Similar to Bavaria, carbonates are located in the east of the Rhenohercynian Massif, in North Rhine-Westphalia (NRW), for which quantification of the geothermal potential is still lacking. Compared to Bavaria, a supraregional carbonate mountain belt is exposed at the Remscheid-Altena anticline (in NRW) from the Upper Devonian and Lower Carboniferous times. The aim of our study was to examine the potential geothermal reservoir by field and laboratory investigations. Therefore, three representative outcrops in Wuppertal, Hagen-Hohenlimburg, and Hönnetal were studied. During field surveys, 1068 discontinuities (139 open fractures without any filling, 213 joints, 413 veins filled with calcite, and 303 fractures filled with debris deposits) at various spatial scales were observed by scanline surveys. These discontinuities were characterized by trace length, true spacing, roughness, aperture, and filling materials. Discontinuity orientation analysis indicated three dominant strike orientations in NNW–SSE, NW–SE, and NE–SW directions within the target horizon of interest. This compacted limestone layer (Massenkalk) is approximately 150 m thick and located at 4000 to 6000 m depth, dipping northwards at a dip angle of about 30 to 40∘. An extrapolation of the measured layer orientation and dip suggests that the carbonate reservoir could hypothetically extend below Essen, Bochum, and Dortmund. Our combined analysis of the field and laboratory results has shown that it could be a naturally fractured carbonate reservoir. We evaluated the potential discontinuity network in the reservoir and its orientation with respect to the prevailing maximum horizontal stress before concluding with implications for fluid flow: we proposed focusing on prominent discontinuities striking NNW–SSE for upcoming geothermal applications, as these (1) are the most common, (2) strike in the direction of the main horizontal stress, (3) have a discontinuity permeability that significantly exceeds that of the reservoir rock matrix, and (4) only about 38 % of these discontinuities were observed with a calcite filling. The remaining discontinuities either showed no filling material or showed debris deposits, which we interpret as open at reservoir depth. Our results indicate that even higher permeability can be expected for karstified formations related to the reef facies and hydrothermal processes. Our compiled data set, consisting of laboratory and field measurements, may provide a good basis for 3D subsurface modelling and numerical prediction of fluid flow in the naturally fractured carbonate reservoir.

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“…Basically, truncation effects explain the influence of underestimating small characteristics due to the resolution of the sampling method, that is, outcrop and/or survey size. Censoring effects occur when large characteristics are incompletely observed due to the outcrop size mentioned or when characteristics are selected due to subjective choice (Priest and Hudson, 1981;Lacazette, 1991). While the trunctuation effects ca be reduced by a sophisticated set of data and resolution, the censoring effect can be reduced depending on the method applied, adapted technology, and the amount of data obtained (Santos et al, 2015).…”

Section: Estimating the Geological Subsurface Model Of The Carbonate mentioning

confidence: 99%

“…The approach we have chosen to use the scanline survey method described by Priest and Hudson (1981) is a widely accepted method for the characterization of fracture networks (e.g., La Pointe and Hudson, 1985;Lacazette, 1991;Narr, 1996). The advantages of the method are especially the acquisition time and the associated verification as well as the acquisition costs compared to other methods (e.g., LIDAR outcrop survey; Wilson et al, 2011).…”

Section: Estimating the Geological Subsurface Model Of The Carbonate mentioning

confidence: 99%

Characterization of fractures in potential reservoir rocks for geothermal applications in the Rhine-Ruhr metropolitan area (Germany)

Balcewicz¹,

Ahrens²,

Lippert³

et al. 2020

Preprint

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Abstract. The importance of research into clean and renewable energy solutions has increased over the last decade. Geothermal energy provision is proven to meet both conditions. Therefore, conceptual models for deep geothermal applications were developed for different field sites regarding different local conditions. In Bavaria, Germany, geothermal applications were successfully carried out in carbonate horizons at depth of 4000 to 6000 m. High permeability rates combined with sufficient thermal conductivities were mainly studied in karstified carbonates from the Late Jurassic reef facies. Similar to Bavaria, carbonates are located in the east of the Rhenohercynian Massif, in North Rhine-Westphalia (NRW), which quantification of the geothermal potential is still lacking. Compared to Bavaria, a supraregional carbonate mountain belt is exposed at the Remscheid-Altena anitcline (NRW) from late Devonian and early Carboniferous times. The aim of our study was to examine the potential geothermal reservoir by field and laboratory investigations. Therefore, three representative outcrops in Wuppertal, Hagen Hohenlimburg, and Hönnetal were studied. During field surveys, 1068 discontinuities at various spacial scales were observed by scanline surveys. These discontinuities were characterized by trace length, true spacing, roughness, aperture, and filling materials. Joint orientation analysis indicated three dominant strike orientations in NNW–SSE, NW–SE, and NE–SW directions within the target horizon of interest. This compacted limestone layer (Massenkalk) is approximately 300 m thick and located at 4000 to 6000 m depth, dipping northwards at a shallow dip angle of about 30 to 40°. An extrapolation of the measured layer orientation and dip suggests that the carbonate reservoir extends below Essen, Bochum, and Dortmund. Our combined analysis of the field and laboratory results has shown that it could be a naturally fractured carbonate reservoir. We evaluated the potential fracture network in the reservoir and its orientation with respect to the prevailing maximum horizontal stress before concluding with implications for fluid flow: We proposed to focus on discontinuities that are approximately N–S oriented for upcoming geothermal applications, because the geothermal potential of the characterized reservoir matrix is insufficient for deep geothermal applications. Our results indicate that even higher permeability can be expected for karstified formations related to the reef facies. Our compiled data set consisting of laboratory and field measurements may provide a good basis for 3D subsurface modeling and numerical prediction of fluid flow in the naturally fractured carbonate reservoir. Further studies have to be elaborated to verify, if the fractured reservoir could possibly be reactivated by, for instance, hydraulic stimulation and thus enable geothermal applications.

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A new stereographic technique for the reduction of scanline survey data of geologic fractures

Cited by 17 publications

References 5 publications

A case for neotectonic joints along the Niagara Escarpment

A case for neotectonic joints along the Niagara Escarpment

Characterization of discontinuities in potential reservoir rocks for geothermal applications in the Rhine-Ruhr metropolitan area (Germany)

Characterization of fractures in potential reservoir rocks for geothermal applications in the Rhine-Ruhr metropolitan area (Germany)

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