Kilometer-scale fault-related thermal anomalies in tight gas sandstones

Wüstefeld, Patrick; Hilse, Ulrike; Lüders, Volker; Wemmer, Klaus; Koehrer, Bastian; Hilgers, Christoph

doi:10.1016/j.marpetgeo.2017.05.015

Cited by 30 publications

(26 citation statements)

References 84 publications

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“…Drozdzewski and Ribbert (2003) noted that the underlying Lower Carboniferous contains marine limestones, shales, chert and clayand siltstones, which are underlain by thick Devonian siliciclastics and carbonates. CO 2 -bearing fluids generated from Lower Carboniferous and Devonian carbonates have been suggested to be the source for CO 2 trapped in Upper Carboniferous and Zechstein vein minerals or fluid inclusions (Biehl et al, 2016;Nadoll et al, 2019;Wüstefeld et al, 2017b).…”

Section: Geological Settingmentioning

confidence: 99%

“…However, hydrothermal fluid circulation in fault zones presents significant exploration and development risks in NW German gas fields producing from Upper Carboniferous tight sandstones (Teichmüller, 1986;Cameron and Ziegler, 1997;Petmecky et al, 1999;Senglaub et al, 2005a;Senglaub et al, 2005b;Lüders et al, 2012). Such high temperature anomalies may result in kilometre-scale zones of significantly reduced reservoir quality, as shown by Wüstefeld et al (2017b). In the Lower Saxony Basin, several causes for the thermal anomalies have been proposed.…”

Section: Introductionmentioning

confidence: 99%

“…the Bramsche Massif) (Teichmüller, 1986;Betz et al, 1987), whereas others have suggested that deep burial could explain the high temperatures (Petmecky et al, 1999;Bruns et al, 2013). The circulation of hydrothermal fluids along faults has recently been documented in the Piesberg area (Wüstefeld et al, 2017b).…”

Section: Introductionmentioning

confidence: 99%

“…A number of studies of Upper Carboniferous sandstones in outcrops in NW Germany have been published focussing on the sedimentology and mineralogy of the deposits, on depositional geometries, and on sequence cyclicity (David, 1990;Sedat et al, 1992;Jones and Glover, 2005). Petrophysical data have been linked to structural and diagenetic characteristics to explain lateral and vertical variations in porosity and permeability (Becker et al, 2017;Wüstefeld et al, 2017a;Wüstefeld et al, 2017b).…”

Section: Introductionmentioning

confidence: 99%

“…In the context of these studies, the present paper aims to link data obtained from three outcrops of Upper Carboniferous fluvial sandstones (at Piesberg, Woitzel and Hüggel) to subsurface data from wells at two gas fields (Fields A and B, drilled by Wells A and B) located approximately 50 km away (Figs 1b and c). Previous studies have investigated reservoir heterogeneities within a particular study area (Becker et al, 2017;Wüstefeld et al, 2017a;Wüstefeld et al, 2017b) and compared them with those at nearby locations (Woitzel and Hüggel outcrops, see Becker et al, 2017;Well A and B, see Busch et al, 2019). The present study integrates different data sets over larger distances with a focus on matrix porosity and permeability variations.…”

Section: Introductionmentioning

confidence: 99%

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Reservoir Quality Evolution of Upper Carboniferous (Westphalian) Tight Gas Sandstones, Lower Saxony Basin, Nw Germany

Becker

Busch

Koehrer³

et al. 2019

Journal of Petroleum Geology

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This paper investigates reservoir quality development in tight Upper Carboniferous fluvial sandstones (Westphalian C/D) in the Lower Saxony Basin, NW Germany. The study integrates data from three outcrops (Piesberg, Woitzel and Hüggel) in the south of the basin with that from two wells (Wells A and B) located at gas fields approximately 50 km to the north. Petrographic and petrophysical data are related to the diagenetic evolution of the sandstones and the burial and structural history of the Lower Saxony Basin. The outcrop and subsurface data sets are compared in order to investigate the factors controlling reservoir quality evolution. Upper Carboniferous fluvial sandstones from the Woitzel and Hüggel outcrops and from Wells A and B have similar matrix permeabilities (0.01 to 10 mD), but matrix porosities vary between Well A (average 6%), Well B (average 10%), Woitzel (average 15%), and Hüggel (average 19%). Permeability reduction during burial is related to the formation of clay mineral cement, which was mainly controlled by variations in both the palaeo‐climate and in the sandstones’ depositional composition. Matrix porosity was controlled by local differences in burial history related to basin inversion tectonics. The greater amount of inversion‐related uplift at Well B (about 2.8 km) resulted in lower thermal exposure of the Westphalian sandstones at this location, which thus show higher matrix porosities than the sandstones at Well A which were uplifted by only about 1.2 km. Further increases in porosity in the outcrop sandstones may be related to the dissolution of carbonate cement during late‐stage uplift in near‐surface conditions. Upper Carboniferous fluvial sandstones from the Piesberg quarry show the poorest reservoir characteristics compared to the samples from the subsurface and the other outcrops, with matrix porosities averaging 6% and permeabilities <0.01 mD. Reservoir quality reduction was controlled by thermal anomalies associated with a large fault at the Piesberg quarry. By contrast, a few outliers in the sample data sets from Well B and the Piesberg quarry, which have permeabilities of more than 100 mD, show that faulting or natural fracturing may enhance reservoir quality within a particular area. Faults/fractures may act as potential migration pathways for leaching fluids, or may provide fracture‐permeability systems with production potential. Depositional setting, burial‐related diagenetic processes and structural characteristics in the Lower Saxony Basin need to be carefully evaluated in order to provide an improved understanding of the reservoir quality of the Upper Carboniferous sandstones.

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Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reservoir Quality Evolution of Upper Carboniferous (Westphalian) Tight Gas Sandstones, Lower Saxony Basin, Nw Germany

Becker

Busch

Koehrer³

et al. 2019

Journal of Petroleum Geology

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Metal budget and origin of aqueous brines depositing deep-seated Zn-Pb mineralization linked to hydrocarbon reservoirs, North German Basin

et al. 2023

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The origin, evolution, and interplay of brine and hydrocarbon fluid systems play a crucial role in the formation of deep sediment-hosted base metal ore deposits. Here we investigate ratios of halogens, noble gases, stable C and S isotopes, and metal budgets of aqueous brines, which deposited deep-seated and near-surface hydrothermal Zn-Pb mineralization hosted by Zechstein carbonates in the Lower Saxony Basin (North German Basin), by studies of fluid inclusions in sphalerite and quartz. Major and trace element geochemistry and noble gas isotopic signatures of brine inclusions revealed that the ore-forming fluids were highly reactive and experienced prolonged interactions with host rocks in the constricted, over-pressured metal source regions and consequently evolved from near-neutral, oxidized brines towards more reduced, acidic high-salinity brines. Quartz-hosted halite-saturated fluid inclusions with Th <200°C contain Zn and Pb concentrations up to ca. 9400 μg g-1 and 5200 μg g-1, respectively, and indicate the efficiency of metal scavenging processes. The interactions with Westphalian coals and Corg-rich shales influenced the redox state as well as the trace and critical element budget of the sphalerite-hosted fluid inclusions, with enrichment in Ge, Pd, Sb, Tl, Bi, and Ag. The salinities of metalliferous fluids originated primarily from seawater evaporation, however in addition a significant halite-dissolution component is present in the southern part of the Lower Saxony Basin. High concentrations of radiogenic noble gases and potassium in the sphalerite-hosted fluid inclusions are ascribed to strong interactions with the Paleozoic siliciclastic sedimentary pile and crystalline basement rocks. Reflux of the strongly modified, sulfur-poor, Zn-Pb-bearing acidic brines, proceeded via re-activated structurally controlled pathways into sour gas or gas-saturated brine pools in the Zechstein Ca2 carbonate unit. Here, mixing of the ascending metal-rich brines with H2S derived from thermochemical sulfate reduction (TSR), resulted in the deposition of deep-seated Zn-Pb ores in the Lower Saxony Basin. The overall timing of the Zn-Pb ore formation can be constrained to the Upper Cretaceous basin inversion.

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Structural evolution of continental and marine Permian rock salt of the North German Basin: constraints from microfabrics, geochemistry and U–Pb ages

Henneberg

Linckens

Schramm

et al. 2020

Int J Earth Sci (Geol Rundsch)

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Analyzing the dynamics of microstructural response on natural deformation in rock salt, we present microfabric, EBSD, geochemical and U–Pb data, obtained from Permian salt formations of the Kiel-Honigsee salt wall in Northern Germany. The samples were recovered from deep drillings, which penetrated through an overturned rock salt sequence of both Rotliegend and Zechstein deposits. The bromide concentration in halite indicates a continental and marine origin for the Rotliegend and Zechstein deposits, respectively. Despite intense deformation, relics of early diagenetic fabrics are still preserved. Deformation of the impure Rotliegend rock salt was accommodated by pressure solution and hydrofracturing as is indicated by the microfabrics and bromide concentration in halite. Fractures in siliciclastic domains were filled with fibrous halite and deformed by subgrain rotation recrystallization (SGR). Fluid-rich Zechstein rock salt, on the other hand, was deformed by formation of subgrains and grain boundary migration (GBM). The distribution of mineral phases and fluids had a significant impact on the fabric evolution and on strain localization. U–Pb dating of carbonate phases of the Rotliegend sequence yielded Permian depositional ages and Jurassic to Cretaceous deformation ages, the latter related to diapiric ascent. The combination of results traces a dynamic evolution of the rock fabric inside the diapir structure driven by locally active deformation processes that can be correlated with early stages of halite deposition and diagenesis and syntectonic fabric reorganization related to diapirism in an extensional setting.

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Kilometer-scale fault-related thermal anomalies in tight gas sandstones

Cited by 30 publications

References 84 publications

Reservoir Quality Evolution of Upper Carboniferous (Westphalian) Tight Gas Sandstones, Lower Saxony Basin, Nw Germany

Reservoir Quality Evolution of Upper Carboniferous (Westphalian) Tight Gas Sandstones, Lower Saxony Basin, Nw Germany

Metal budget and origin of aqueous brines depositing deep-seated Zn-Pb mineralization linked to hydrocarbon reservoirs, North German Basin

Structural evolution of continental and marine Permian rock salt of the North German Basin: constraints from microfabrics, geochemistry and U–Pb ages

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