Sedimentology, stratigraphy, and reservoir properties of an unconventional, shallow, frozen petroleum reservoir in the Cretaceous Nanushuk Formation at Umiat field, North Slope, Alaska

Shimer, Grant; McCarthy, Paul J.; Hanks, Catherine L.

doi:10.1306/09031312239

Cited by 15 publications

(5 citation statements)

References 40 publications

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“…In the Umiat area, the lower Nanushuk Formation is thought to be mid-Albian in age based on plant fossils (Spicer and Herman, 2010) and ammonites (Imlay, 1961). A late Albian 40 Ar/ 39 Ar age from the upper Nanushuk Formation is consistent with the biostratigraphy, as the underlying sediments of the lower Nanushuk are separated from the upper Nanushuk Formation by a major flooding surface and over 100 m of shale (Shimer et al, 2014;Fig. 8).…”

Section: Albian-cenomanian Bentonites: Nanushuk Seabee and Tuluvak mentioning

confidence: 64%

“…This sample, just above the base of the Seabee Formation, has an age of 98.2  0.8 Ma, placing it in the early Cenomanian. Approximately 25 km to the northeast, a major flooding surface lies between the upper Nanushuk Formation and Shale Wall facies of the Seabee Formation (Houseknecht and Schenk, 2005;Shimer et al, 2014).…”

Section: Albian-cenomanian Bentonites: Nanushuk Seabee and Tuluvak mentioning

confidence: 99%

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40Ar/39Ar ages and geochemical characterization of Cretaceous bentonites in the Nanushuk, Seabee, Tuluvak, and Schrader Bluff formations, North Slope, Alaska

Shimer

Benowitz

Layer

et al. 2016

Cretaceous Research

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Diagenetically altered volcanic ash deposits (bentonites) found in Cretaceous terrestrial and marine foreland basin sediments have the potential to be used for chronostratigraphy and subsurface correlation across Alaska's North Slope. Detailed age and geochemical studies of these volcanogenic deposits may also shed light on the tectonic evolution of the Arctic. Though these bentonites have been previously studied, there are few published results for regional bentonite ages and geochemistry due to challenges of dating weathered volcanic ash. We analyzed mineral separates from cored bentonites recovered from wells in the National Petroleum Reserve Alaska. The analyses confirm that an intense period of volcanic ash deposition on Alaska's North Slope began by the late Albian and was persistent throughout the Cenomanian, a period of rapid progradation and aggradation in the Colville basin. These results also add to a sparse record of radioisotopic ages from the Nanushuk Formation. A bentonite preserved in delta plain sediments in the upper Nanushuk Formation dates to 102.6 ± 1.5 Ma (late Albian), while a bentonite near the base of the overlying Seabee Formation was deposited at 98.2 ± 0.8 Ma, in the early Cenomanian. The two ages bracket a major flooding surface at the base of the Seabee Formation near Umiat, Alaska, placing it near the Albian-Cenomanian boundary (100.5 Ma). Several hundred feet up-section, the non-marine Tuluvak Formation contains bentonites with 40 Ar/ 39 Ar ages of 96.7 ± 0.7 to 94.2 ± 0.9 Ma (Cenomanian), several million years older than previously published K-Ar ages and biostratigraphic constraints suggest. Major and trace element geochemistry of a sub-sample of six bentonites from petroleum exploration wells at Umiat show a range in composition from andesite to rhyolite, with a continental arc source. The bentonites become more felsic from the late Albian (~102 Ma) to late Cenomanian (~94 Ma). A likely source for the bentonites is the Okhotsk-Chukotka Volcanic Belt (OCVB) of eastern Siberia, a continental arc which became active in the Albian and experienced episodes of effusivity throughout the Late Cretaceous. Chronostratigraphically anomalous 40 Ar/ 39 Ar ages coincide with peaks of magmatic activity in the OCVB, suggesting that these anomalously old ages may be due to magmatic contribution of xenocrysts or recycling of detrital minerals from older volcanic events. An alternative explanation for the chronostratigraphically anomalous ages is mixing of bentonites with detrital sediment derived from unroofing and erosion of metamorphic rocks in the Brooks Range, Herald Arch, and Chukotka throughout the mid to Late Cretaceous. range of ages within the context of known biostratigraphy (Tappan, 1960; Mull et al., 2003; Spicer and Herman, 2010) and regional volcanic events (Moore et al., 1994; Tikhomirov et al., 2012; Akinin et al., 2014). In conjunction with 40 Ar/ 39 Ar age interpretations, we classify magma composition and tectonic origin for six bentonites from the Umiat wells using major and t...

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Section: Albian-cenomanian Bentonites: Nanushuk Seabee and Tuluvak mentioning

confidence: 64%

Section: Albian-cenomanian Bentonites: Nanushuk Seabee and Tuluvak mentioning

confidence: 99%

40Ar/39Ar ages and geochemical characterization of Cretaceous bentonites in the Nanushuk, Seabee, Tuluvak, and Schrader Bluff formations, North Slope, Alaska

Shimer

Benowitz

Layer

et al. 2016

Cretaceous Research

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“…Ahlbrandt et al [21] and Huffman et al [20] indicated that both delta complexes were river dominated, but they also suggested that the Umiat delta complex was affected by greater wave reworking. Recent work suggests that river-and wave-reworking of delta complexes varies temporally as well as spatially in the eastern Nanushuk Fm., with initial wave dominance followed by subsequent river influence in shallower, more wave-limited conditions created by earlier parasequence progradation and shelf construction [26].…”

Section: Geologic Frameworkmentioning

confidence: 99%

New Dinosaur Ichnological, Sedimentological, and Geochemical Data from a Cretaceous High-Latitude Terrestrial Greenhouse Ecosystem, Nanushuk Formation, North Slope, Alaska

Fiorillo,

McCarthy,

Shimer

et al. 2024

Geosciences

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The Nanushuk Formation (Albian–Cenomanian) crops out over much of the central and western North Slope of Alaska, varying from ≈1500 to ≈250 m thick from west to northeast. The Nanushuk Formation records an inter-tonguing succession of marine and nonmarine conglomerate, sandstone, mudstone, and coal. These rock units comprise the Kukpowruk and Corwin formations of the former Nanushuk Group, respectively. Work presented here is centered in the foothills of the DeLong Mountains along the Kukpowruk River, from an area west of Igloo Mountain in the Coke Basin to the Barabara Syncline, approximately 80 km to the north. A radiometric date recovered from a tuff in our study area suggests a Cenomanian age for at least some of these rocks. Outcrops along the Kukpowruk River contain a well-preserved fossil flora previously recovered from marine, marginal marine, and terrestrial sediments. Our own work focuses on detailed measured sections of terrestrial rocks, interpretation of sedimentary facies and facies associations, and documentation of fossil vertebrates. Eight facies associations are identified in the study area that together are interpreted to represent meandering fluvial and upper delta plain environments. Plant fossils are common and include standing tree trunks up to 58 cm in diameter at some locations. Approximately 75 newly discovered tracksites, and a heretofore unknown, rich fossil vertebrate ichnofauna, are present. The ichnofaunal assemblage includes evidence of small and large theropod dinosaurs (including birds) and bipedal and quadrupedal ornithischian dinosaurs. Approximately 15% of the dinosaur ichnofauna record is represented by fossil bird tracks. Wood fragments from the Nanushuk Formation were analyzed for their carbon isotopic composition to relate δ13C to mean annual precipitation. Samples averaged −26.4‰ VPDB, suggesting an average MAP of 1412 mm/year. This record of increased precipitation in the Nanushuk Fm. during the mid-Cretaceous provides new data that supports global precipitation patterns associated with the Cretaceous Thermal Maximum. This work provides an important framework for much-needed further paleoecological and paleoclimatic analyses into greenhouse conditions in the terrestrial Cretaceous Arctic during this important window in time.

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“…The Cretaceous Nanushuk Formation primarily consists of mudstone and coarsening-upward sequences of sandstone deposits that were deposited in fluvio-deltaic, shoreface, and marine-shelf environments [12,13] (Figure 2). Limited core data combined with outcrop observations show that the Nanushuk Formation has been subdivided into five lithologic units-the uppermost shallow marine Ninuluk sandstone unit, the deltaic Killik Tongue of the Chandler Formation, the underlying shallow marine to deltaic Upper and Lower Grandstand sandstone units that are separated by marine mudstones, and shales of the Tuktu [8]. Deltaic sandstones of the Lower Grandstand Formation are the primary exploration target in the Umiat Oil Field.…”

Section: Umiat Oil Fieldmentioning

confidence: 99%

“…Reference geologic map, well locations, and a generalized cross-section of the Umiat Oil Field, Alaska. Modified from Shimer et al, 2014[8].…”

mentioning

confidence: 99%

Machine Learning-Based Probabilistic Lithofacies Prediction from Conventional Well Logs: A Case from the Umiat Oil Field of Alaska

Dixit

McColgan²,

Kusler

2020

Energies

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A good understanding of different rock types and their distribution is critical to locate oil and gas accumulations in the subsurface. Traditionally, rock core samples are used to directly determine the exact rock facies and what geological environments might be present. Core samples are often expensive to recover and, therefore, not always available for each well. Wireline logs provide a cheaper alternative to core samples, but they do not distinguish between various rock facies alone. This problem can be overcome by integrating limited core data with largely available wireline log data with machine learning. Here, we presented an application of machine learning in rock facies predictions based on limited core data from the Umiat Oil Field of Alaska. First, we identified five sandstone reservoir facies within the Lower Grandstand Member using core samples and mineralogical data available for the Umiat 18 well. Next, we applied machine learning algorithms (ascendant hierarchical clustering, self-organizing maps, artificial neural network, and multi-resolution graph-based clustering) to available wireline log data to build our models trained with core-driven information. We found that self-organizing maps provided the best result among other techniques for facies predictions. We used the best self-organizing maps scheme for predicting similar reservoir facies in nearby uncored wells—Umiat 23H and SeaBee-1. We validated our facies prediction results for these wells with observed seismic data.

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Sedimentology, stratigraphy, and reservoir properties of an unconventional, shallow, frozen petroleum reservoir in the Cretaceous Nanushuk Formation at Umiat field, North Slope, Alaska

Cited by 15 publications

References 40 publications

40Ar/39Ar ages and geochemical characterization of Cretaceous bentonites in the Nanushuk, Seabee, Tuluvak, and Schrader Bluff formations, North Slope, Alaska

40Ar/39Ar ages and geochemical characterization of Cretaceous bentonites in the Nanushuk, Seabee, Tuluvak, and Schrader Bluff formations, North Slope, Alaska

New Dinosaur Ichnological, Sedimentological, and Geochemical Data from a Cretaceous High-Latitude Terrestrial Greenhouse Ecosystem, Nanushuk Formation, North Slope, Alaska

Machine Learning-Based Probabilistic Lithofacies Prediction from Conventional Well Logs: A Case from the Umiat Oil Field of Alaska

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