1,054 research outputs found
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Comparative Anatomy and Petrophysical Property Structure of Seaward- and Landward- Stepping Deltaic Reservoir Analogs, Ferron Sandstone, Utah
The recovery of natural gas from fluvial-deltaic reservoirs is governed by complex internal architectures. To aid in the translation of outcrop geology to reservoir equivalents, all existing Ferron outcrop, petrophysical, and subsurface data have been integrated into a geologic model of reservoir heterogeneity that compares and contrasts seaward- and landward-stepping stratigraphic cycles. Reservoir architecture varies in a predictable fashion between seaward- and landward-stepping stratigraphic cycles. Within seaward-stepping units, delta-front strata are highly compartmentalized by marine and marginal marine shales coincident with stratigraphic cycle, parasequence, and mouth-bar bounding surfaces. Coeval distributaries are volumetrically a minor component and are preserved as ribbon-like sand bodies encased in finer-grained strata. By contrast, within landward-stepping units, parasequences and component mouth-bar deposits are amalgamated into a lithologically homogeneous strike-elongate sand body. Coeval distributaries are volumetrically a major component and are preserved as a complex network of interconnected, lithologically diverse sand bodies. Internal heterogeneities, related to floodplain, abandoned channel fill, and mud-clast lag deposits, severely disrupt lateral and vertical continuity. Analysis of the Ferron gas field reveals that favorable sites for stratigraphic entrapment occur where proximal and distal portions of parasequences pinch out into lagoonal and marine mudstones, respectively.Bureau of Economic Geolog
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Quantification of Flow Unit and Bounding Element Properties and Geometries, Ferron Sandstone, Utah: Implications for Heterogeneity in Gulf Coast Tertiary Deltaic Reservoirs
Outcrop exposures are being studied to quantify the internal permeability distribution of fluvial-deltaic sandstones, which results in reservoir compartments bounded by baffles or barriers to gas flow. This information will be used to develop reservoir models that can guide infill drilling to optimize incremental gas reserve growth from sandstone reservoirs. The objectives are being accomplished through integration of (1) outcrop characterization, (2) petrophysical measurements, and (3) pore-level modeling.
Projected long-term benefits of the study are two-fold. First, increased understanding of internal architecture and improved methods for quantification of heterogeneity will facilitate development of strategies to minimize risk in the extended development of fluvial-dominated deltaic gas reservoirs. Second, targeting of incremental gas resources in mature reservoirs will lead to extended recovery of a low-cost, low-risk resource.
Results of the first year of studies show that the architecture, geometry, and internal permeability distribution of fluvial-deltaic sandstones are generally predictable and that a four-order hierarchy of bounding surfaces exists. Initial tests have been completed, and reliable measurements of petrophysical properties of flow units, flow baffles, and flow barriers are being performed on outcrop samples. Development of a pore-level simulator has been essentially completed. Results, in general, indicate that the field approach is sound and that information gained on outcrop can be used to produce realistic reservoir models.Bureau of Economic Geolog
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Quantification of Flow Unit and Bounding Element Properties and Geometries, Ferron Sandstone, Utah: Implications for Heterogeneity in Gulf Coast Tertiary Deltaic Reservoirs
Outcrop mapping, field permeability measurements, petrographic analyses, petrophysical measurements, and pore-level modeling studies are being conducted on exposures of the Ferron Sandstone, east-central Utah, to develop a better understanding of the dimensions and internal arrangement of flow units, baffles, and barriers in sandstone gas reservoirs. The ultimate goals of this work are to establish methods for applying outcrop studies to reservoir characterization and to develop reservoir models that will guide infill drilling to maximize incremental gas reserve growth from fluvial-deltaic sandstone reservoirs.
Activities during the second year of this 3-year project focused on data collection and preliminary interpretations. Mapping and field permeability measurements were initiated on the seaward-stepping Ferron unit 2 sandstone. These results will provide a comparison with data collected during the 1990 field season when landward-stepping sandstones of Ferron unit 3 were examined. Framework grain and cement mineralogy and the composition of intergranular material were quantified for selected samples from unit 3. Petrophysical measurements were completed on 24 specimens from units 2, 4, and 3. Sections of the pore-level modeling code were rewritten to improve accuracy and efficiency, and scenarios were developed to model the effects of grain size, cementation, and compaction on porosity, single-phase permeability, and formation factor.
Preliminary results indicate that important differences exist in the internal geometry of landward- and seaward-stepping fluvial-deltaic sandstones. It was also found that closer-spaced permeability measurements improved the resolution of permeability structure. Petrographic studies documented differences in composition between fluvial, transgressive, delta-front, and distributary-channel sandstones; these differences in rock composition are reflected by differences in the mean permeability of these facies as measured on outcrop. Initial comparisons of pore-level model results with measured petrophysical properties are encouraging and suggest that refinements based on examination of the analyzed samples will lead to a close match between observed and modeled behavior.Bureau of Economic Geolog
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Quantifying Reservoir Heterogeneity Through Outcrop Characterization: 1. Architecture, Lithology, and Permeability Distribution of a Seaward-Stepping Fluvial-Deltaic Sequence, Ferron Sandstone (Cretaceous), Central Utah
The internal architecture of natural gas reservoirs fundamentally controls production efficiency and the volume of gas unrecovered at abandonment. To better understand reservoir complexity, we investigated relations between sandstone architecture and permeability structure of landward-stepping (wave-modified) Ferron deltaic sandstones exposed in central Utah. Deltaic sandstones extend 4 mi along sediment-transport direction in the landward-stepping Ferron genetic sequence GS 5. Most sand was deposited in transgressive, delta-front, and distributary-channel facies. Distributary channels constitute the principal reservoir facies because mean permeability in distributary-channel sandstones is approximately twice that of delta-front and transgressive sandstones, and because distributary-channel sandstones are well developed. Channel architecture, bounding-surface character, and permeability distribution change systematically from landward to seaward position in the system. Near the landward limit, mean permeability is 300 md, mud occurs as clasts along channel-flank bounding surfaces, and permeability systematically decreases upward. Near the seaward extent of the system, mean permeability is 750 md, mud is segregated into discrete strata-bounding sand bodies, and vertical permeability trends are uniformly high. Statistical analysis shows that lithofacies are the fundamental sandstone architectural units. Similar lithofacies have similar permeability character, regardless of position in the facies tract. Variable preservation of lithofacies controls permeability distribution throughout the channel system. Semivariogram analysis shows that vertical and horizontal permeability correlation distances correspond to distances between bounding surfaces and to sand-body dimensions. Diagenetic overprint is minor, owing to low burial temperatures.Bureau of Economic Geolog
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Quantifying Reservoir Heterogeneity Through Outcrop Characterization: 2. Architecture, Lithology, and Permeability Distribution of a Seaward-Stepping Fluvial-Deltaic Sequence, Ferron Sandstone (Cretaceous), Central Utah
The internal architecture of natural gas reservoirs fundamentally determines gas migration, production efficiency, and the volume of gas unrecovered at abandonment. To determine the style and scale of reservoir complexity in fluvially dominated (seaward-stepping) deltaic reservoirs, we investigated relations between sandstone architecture and permeability distribution in seaward-stepping deltaic Ferron genetic sequence (GS) 2 sandstone outcrops in central Utah. Distributary-channel, mouth-bar, and delta-front deposits are the volumetrically important sand repositories in the Ferron GS 2. Mouth-bar facies are laterally extensive and relatively simple sand bodies with moderate mean permeabilities. Distributary channels also have good permeability but are narrow, sinuous, and separated from mouth-bar sandstones by low-permeability bounding surfaces, making them difficult targets for development. Statistical analyses of permeability data show that lithofacies are the fundamental sandstone architectural elements. Therefore, lithofacies are the basic units that should be used to construct reservoir models. The variable preservation of lithofacies controls permeability throughout the system. Vertical and horizontal permeability correlation distances correspond to distances between bounding surfaces and to macroform dimensions. Estimates based on field-scale mapping show that 91 percent of the reservoir area could be contacted at 320-acre well spacing. Sandstone architecture and permeability relations of the Ferron GS 2 are similar to those in Lake Creek (Wilcox Group, Texas Gulf Coast) reservoirs. This outcrop-reservoir comparison confirms that outcrop data are transferable to reservoirs.Bureau of Economic Geolog
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Memorandum of Understanding Between the United States Department of Energy and the State of Texas - Characterization of Oil and Gas Reservoir Heterogeneity
Ultimate recovery from Texas oil reservoirs at current technological and development levels is projected to be 36 percent of the oil in place. Thus, of the 165 billion barrels (Bbbl) of oil discovered statewide, 106 Bbbl will remain in existing reservoirs after recovery of proved reserves. This remaining resource is composed of residual oil (71 Bbbl) and mobile oil (35 Bbbl). The remaining mobile oil is conventionally recoverable but is prevented from migrating to the wellbore by intrareservoir seals or bounding surfaces.
Reservoir architecture, the internal fabric or structure of reservoirs, governs paths of fluid migration during oil and gas production. Reservoir architecture is, in turn, the product of the depositional and diagenetic processes responsible for the origin of the reservoir. If an understanding of the origin of the reservoir is developed, reservoir architecture, and therefore the paths of fluid migration, become predictable. Thus, with a greater understanding of the fabric of the reservoir and its inherent control on the paths of fluid flow, we can more efficiently design and implement advanced recovery strategies.Bureau of Economic Geolog
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Chararcterization of Heterogeneity Style and Permeability Structure in Fluvial Reservoirs
The Cretaceous Acu Formation was investigated as an analog to a heterogeneous group of reservoirs having significant potential for reserve growth in the Potiguar Basin of Brazil. Architectural, lithologic, and petrophysical information was collected from an outcrop exposing a fluvially deposited sandstone body located in the state of Rio Grande do Norte, Brazil. Sedimentologic descriptions of the sandstone body were collected from a series of vertical transects spaced evenly across the outcrop. Stratal surfaces traced between transects were recorded on photomosaics. Measurements of permeability were obtained from each transect by use of a portable probe-style mechanical field permeameter. A cross-section depicting bedding architecture, sedimentologic attributes, and permeability values was constructed, and the information incorporated into a two-dimensional representation of reservoir architecture using Stratamodel's Stratigraphic Geocellular Modeling software (SGM). The SGM technique deterministically interpolates permeability data between transect locations using a lithologic or stratigraphic framework.Bureau of Economic Geolog
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Application of Advanced Reservoir Characterization, Simulation, and Production Optimization Strategies to Maximize Recovery in Slope and Basin Clastic Reservoirs, West Texas (Delaware Basin)
The objective of this Class III project is to demonstrate that detailed reservoir
characterization of elastic reservoirs in basinal sandstones of the Delaware Mountain Group in
the Delaware Basin of West Texas and New Mexico is a cost-effective way to recover more of
the original oil in place by strategic infill-well placement and geologically based enhanced oil
recovery. The study focused on the Ford Geraldine unit, which produces from the upper Bell
Canyon Formation (Ramsey sandstone). Reservoirs in this and other Delaware Mountain Group
fields have low producibility (average recovery <14 percent of the original oil in place) because
of a high degree of vertical and lateral heterogeneity caused by depositional processes and post-depositional
diagenetic modification.
Outcrop analogs were studied to better interpret the depositional processes that formed the
reservoirs at the Ford Geraldine unit and to determine the dimensions of reservoir sandstone
bodies. Facies relationships and bedding architecture within a single genetic unit exposed in
outcrop in Culberson County, Texas, suggest that the sandstones were deposited in a system of
channels and levees with attached lobes that initially prograded basinward, aggraded, and then
stepped around and stepped back toward the shelf. Channel sandstones are 10 to 60 ft thick and
200 to 3,000 ft wide. The flanking levees have a wedge-shaped geometry and are composed of
interbedded sandstone and siltstone; thickness varies from 3 to 20 ft and length from several
hundred to several thousands of feet. The lobe sandstones are broad lens-shaped bodies;
thicknesses range up to 30 ft with aspect ratios (width/thickness) of 100 to 10,000. Lobe
sandstones may be interstratified with laminated siltstones.Bureau of Economic Geolog
Relative exposure to microplastics and prey for a pelagic forage fish
© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Chavarry, J. M., Law, K. L., Barton, A. D., Bowlin, N. M., Ohman, M. D., & Choy, C. A. Relative exposure to microplastics and prey for a pelagic forage fish. Environmental Research Letters, 17(6), (2022): 064038, https://doi.org/10.1088/1748-9326/ac7060.In the global ocean, more than 380 species are known to ingest microplastics (plastic particles less than 5 mm in size), including mid-trophic forage fishes central to pelagic food webs. Trophic pathways that bioaccumulate microplastics in marine food webs remain unclear. We assess the potential for the trophic transfer of microplastics through forage fishes, which are prey for diverse predators including commercial and protected species. Here, we quantify Northern Anchovy (Engraulis mordax) exposure to microplastics relative to their natural zooplankton prey, across their vertical habitat. Microplastic and zooplankton samples were collected from the California Current Ecosystem in 2006 and 2007. We estimated the abundance of microplastics beyond the sampled size range but within anchovy feeding size ranges using global microplastic size distributions. Depth-integrated microplastics (0–30 m depth) were estimated using a depth decay model, accounting for the effects of wind-driven vertical mixing on buoyant microplastics. In this coastal upwelling biome, the median relative exposure for an anchovy that consumed prey 0.287–5 mm in size was 1 microplastic particle for every 3399 zooplankton individuals. Microplastic exposure varied, peaking within offshore habitats, during the winter, and during the day. Maximum exposure to microplastic particles relative to zooplankton prey was higher for juvenile (1:23) than adult (1:33) anchovy due to growth-associated differences in anchovy feeding. Overall, microplastic particles constituted fewer than 5% of prey-sized items available to anchovy. Microplastic exposure is likely to increase for forage fishes in the global ocean alongside declines in primary productivity, and with increased water column stratification and microplastic pollution.This work originated from the Plastic Awareness Global Initiative (PAGI) international workshop, hosted by the Center for Marine Biodiversity and Conservation (CMBC) at Scripps Institution of Oceanography at the University of California San Diego in 2018, with support from Igor Korneitchouk and the Wilsdorf Mettler Future Foundation. We thank the workshop participants for early discussions and a collaborative meeting space. We thank Kelly Lance for her illustration contributions, and the SIO Communications Office for their support. We thank Miriam Doyle and Ryan Rykaczewski for their assistance in data acquisition, and we thank Penny Dockry and Stuart Sandin of CMBC for administrative and logistical support. Julia Chavarry was supported by the San Diego Fellowship. This paper is a contribution from the California Current Ecosystem Long Term Ecological Research site, supported by the National Science Foundation
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ASSESSMENT OF STREAM FISH MORTALITY FROM SHORT-TERM EXPOSURE TO ILLITE CLAYS USED AS AN IN SITU METHOD FOR REMEDIATING 137CS CONTAMINATED WETLANDS
Due to their physical properties, illite clays can sorb cesium-137 almost irreversibly, and therefore sequester contamination from the environment. However, applying large amounts of clay to natural aquatic habitats for in situ remediation purposes may create conditions of high turbidity and sedimentation. To evaluate potential effects of turbidity from illite application on survivorship of stream fish, yellowfin shiners (Notropis lutipinnis) and tessellated darters (Etheostoma olmstedi) were subjected to treatment with two different types of clay in flow-through simulated stream raceways. Turbidity and fish mortality were subsequently monitored for seven days. At 2-m downstream from the application point, mean turbidity peaked during clay application at 525 and 72 nephelometric turbidity units (NTU) in the air-floated illite and semi-dry illite treatments, respectively. Turbidity returned to levels similar to that of the controls (4-6 NTU) after four hours in the air-floated illite raceways and one hour in the semi-dry illite raceways. Although the majority of the suspended clay was quickly flushed from the system and the remaining settled to the bottom, turbidity did continue to fluctuate because of fish movements and sediment resuspension. Fish mortality did not significantly differ among control and illite treated raceways
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