Many fossil-barren or poorly fossiliferous red bed units are found in the North, Norwegian, and B... more Many fossil-barren or poorly fossiliferous red bed units are found in the North, Norwegian, and Barents seas. Due to the near-absence of biostratigraphic markers in these units, and the possibility of unconformities at their upper and lower boundaries, determining their depositional ages and stratigraphic assignment can be challenging. We apply in-situ U-Pb carbonate dating on North Sea samples, including plant-root related carbonates (rhizoliths) from paleosols and calcite veins crosscutting clasts in a conglomeratic red bed unit, to constrain their respective ages. Our data indicate that one of the studied units was deposited ca. 260 to 250 Ma (Ma – millions of years ago) and may represent an early development of the Skagerrak Formation. The second unit yielded an oldest age of 180.2 ± 9.7 Ma, interpreted to represent a late diagenetic event rather than deposition. High Mn/Sr and low δ 13 C values in many cements dated between ca. 180 to 100 Ma are interpreted to represent precip...
The Released Wells Initiative is a joint industry project administrated and organized by the Norw... more The Released Wells Initiative is a joint industry project administrated and organized by the Norwegian Oil and Gas Association and funded by the majority of companies operating on the Norwegian Continental Shelf (NCS). The project is unique on a worldwide scale, as it will analyze every drill cutting sample from every exploration and appraisal well in the Norwegian national archive. The archive contains about 700,000 samples of unwashed ditch cuttings from more than 1900 wells. Each sample is washed and dried according to a consistent automated procedure, and preserved both in a digital format, using high-resolution white light (WL) and UV (UV) photography and X Ray Fluorescence (XRF) analysis. The cleaned samples from all the wells are available for future analysis. The eighty most recently released wells were subjected to an extended suite of measurements: X-Ray Diffraction (XRD), automated mineralogy (QEMSCAN), Infrared spectroscopy (IRS) and total organic carbon measurement (TOC...
A late Carboniferous to early Permian carbonate and evaporite succession from the Finnmark Platfo... more A late Carboniferous to early Permian carbonate and evaporite succession from the Finnmark Platform (southern Barents Sea) contains nodules of anhydrite partially to fully replaced by calcite spar and native sulfur genetically linked to hydrocarbon migration and/or oxidation, analogous to processes observed in salt diapir caprocks in the Gulf of Mexico. In situ U-Pb dating of this calcite spar therefore has the potential to directly date hydrocarbon migration and provide further insight into the geochemical and temperature conditions during this event when coupled with traditional stable and clumped isotope ratios (δ13C, δ18O, and Δ47). Results indicate calcite formed ca. 50–15 Ma, postdating host-rock deposition by 250–285 m.y. Strongly negative δ13C values in the calcite spar (mean = −15‰) are consistent with a major contribution of carbon from hydrocarbons, and Δ47 paleothermometry indicates a mean precipitation temperature of 46 ± 11 °C. These geochemical results are consistent ...
The Upper Triassic - Lower Jurassic Are Formation comprising the deeper reservoir in the Heidrun ... more The Upper Triassic - Lower Jurassic Are Formation comprising the deeper reservoir in the Heidrun Field offshore mid-Norway consists of fluvial channel sandstones (FCH), floodplain fines (FF), and sandy and muddy bay-fill sediments (SBF, MBF) deposited in an overall transgressive fluvial to lower delta plain regime. The formation has been investigated to examine possible sedimentary facies controls on the distribution of cementation and compaction based on petrography and SEM/micro probe analyses of core samples related to facies associations and key stratigraphic surfaces. The most significant authigenic minerals are kaolinite, calcite and siderite. Kaolinite and secondary porosity from dissolution of feldspar and biotite are in particular abundant in the fluvial sandstones. The carbonate minerals show complex compositional and micro-structural variation of pure siderite (Sid I), Mg-siderite (Sid II), Fe-dolomite, ankerite and calcite, displaying decreasing Fe from early to late dia...
Multivariate analysis is employed to investigate the structure of variations within highly hetero... more Multivariate analysis is employed to investigate the structure of variations within highly heterogeneous data. Traditionally, principal component analysis (PCA) is run by analyzing the entire wireline log and using PCA scores to characterize variability within and between lithologies. In this paper, we propose a technique using only specific subsets of all well records to quantify reservoir heterogeneity due to second order lithological variability. These subsets are chosen from uniform lithofacies parts of the wireline log in order to reduce the variability in the correlation matrix that otherwise would cause lithological changes. The purpose is to assess the efficiency of structured PCA in analyzing small-scale heterogeneity that is captured by wireline logs but often masked by traditional PCA approaches. This paper shows that a structured PCA procedure based upon special lithological units is superior to an unstructured PCA, when the focus is within lithology variations. This structured procedure is applied to data from the Heidrun field, offshore mid-Norway. The results demonstrate clear benefits from added insight into the variability of a complex fluviodeltaic heterolithic sequence that poses great challenges to hydrocarbon development.
Many fossil-barren or poorly fossiliferous red bed units are found in the North, Norwegian, and B... more Many fossil-barren or poorly fossiliferous red bed units are found in the North, Norwegian, and Barents seas. Due to the near-absence of biostratigraphic markers in these units, and the possibility of unconformities at their upper and lower boundaries, determining their depositional ages and stratigraphic assignment can be challenging. We apply in-situ U-Pb carbonate dating on North Sea samples, including plant-root related carbonates (rhizoliths) from paleosols and calcite veins crosscutting clasts in a conglomeratic red bed unit, to constrain their respective ages. Our data indicate that one of the studied units was deposited ca. 260 to 250 Ma (Ma – millions of years ago) and may represent an early development of the Skagerrak Formation. The second unit yielded an oldest age of 180.2 ± 9.7 Ma, interpreted to represent a late diagenetic event rather than deposition. High Mn/Sr and low δ 13 C values in many cements dated between ca. 180 to 100 Ma are interpreted to represent precip...
The Released Wells Initiative is a joint industry project administrated and organized by the Norw... more The Released Wells Initiative is a joint industry project administrated and organized by the Norwegian Oil and Gas Association and funded by the majority of companies operating on the Norwegian Continental Shelf (NCS). The project is unique on a worldwide scale, as it will analyze every drill cutting sample from every exploration and appraisal well in the Norwegian national archive. The archive contains about 700,000 samples of unwashed ditch cuttings from more than 1900 wells. Each sample is washed and dried according to a consistent automated procedure, and preserved both in a digital format, using high-resolution white light (WL) and UV (UV) photography and X Ray Fluorescence (XRF) analysis. The cleaned samples from all the wells are available for future analysis. The eighty most recently released wells were subjected to an extended suite of measurements: X-Ray Diffraction (XRD), automated mineralogy (QEMSCAN), Infrared spectroscopy (IRS) and total organic carbon measurement (TOC...
A late Carboniferous to early Permian carbonate and evaporite succession from the Finnmark Platfo... more A late Carboniferous to early Permian carbonate and evaporite succession from the Finnmark Platform (southern Barents Sea) contains nodules of anhydrite partially to fully replaced by calcite spar and native sulfur genetically linked to hydrocarbon migration and/or oxidation, analogous to processes observed in salt diapir caprocks in the Gulf of Mexico. In situ U-Pb dating of this calcite spar therefore has the potential to directly date hydrocarbon migration and provide further insight into the geochemical and temperature conditions during this event when coupled with traditional stable and clumped isotope ratios (δ13C, δ18O, and Δ47). Results indicate calcite formed ca. 50–15 Ma, postdating host-rock deposition by 250–285 m.y. Strongly negative δ13C values in the calcite spar (mean = −15‰) are consistent with a major contribution of carbon from hydrocarbons, and Δ47 paleothermometry indicates a mean precipitation temperature of 46 ± 11 °C. These geochemical results are consistent ...
The Upper Triassic - Lower Jurassic Are Formation comprising the deeper reservoir in the Heidrun ... more The Upper Triassic - Lower Jurassic Are Formation comprising the deeper reservoir in the Heidrun Field offshore mid-Norway consists of fluvial channel sandstones (FCH), floodplain fines (FF), and sandy and muddy bay-fill sediments (SBF, MBF) deposited in an overall transgressive fluvial to lower delta plain regime. The formation has been investigated to examine possible sedimentary facies controls on the distribution of cementation and compaction based on petrography and SEM/micro probe analyses of core samples related to facies associations and key stratigraphic surfaces. The most significant authigenic minerals are kaolinite, calcite and siderite. Kaolinite and secondary porosity from dissolution of feldspar and biotite are in particular abundant in the fluvial sandstones. The carbonate minerals show complex compositional and micro-structural variation of pure siderite (Sid I), Mg-siderite (Sid II), Fe-dolomite, ankerite and calcite, displaying decreasing Fe from early to late dia...
Multivariate analysis is employed to investigate the structure of variations within highly hetero... more Multivariate analysis is employed to investigate the structure of variations within highly heterogeneous data. Traditionally, principal component analysis (PCA) is run by analyzing the entire wireline log and using PCA scores to characterize variability within and between lithologies. In this paper, we propose a technique using only specific subsets of all well records to quantify reservoir heterogeneity due to second order lithological variability. These subsets are chosen from uniform lithofacies parts of the wireline log in order to reduce the variability in the correlation matrix that otherwise would cause lithological changes. The purpose is to assess the efficiency of structured PCA in analyzing small-scale heterogeneity that is captured by wireline logs but often masked by traditional PCA approaches. This paper shows that a structured PCA procedure based upon special lithological units is superior to an unstructured PCA, when the focus is within lithology variations. This structured procedure is applied to data from the Heidrun field, offshore mid-Norway. The results demonstrate clear benefits from added insight into the variability of a complex fluviodeltaic heterolithic sequence that poses great challenges to hydrocarbon development.
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Papers by Erik Hammer