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

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

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

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

Norton Healthcare: A Strong Payer-Provider Partnership for the Journey to Accountable Care

Examines the progress of an integrated healthcare delivery system in forming an accountable care organization with payer partners as part of the Brookings-Dartmouth ACO Pilot Program, including a focus on performance measurement and reporting

HealthCare Partners: Building on a Foundation of Global Risk Management to Achieve Accountable Care

Describes the progress of a medical group and independent practice association in forming an accountable care organization by working with insurers as part of the Brookings-Dartmouth ACO Pilot Program. Lists lessons learned and elements of success

An Inversion Method for Measuring Beta in Large Redshift Surveys

A precision method for determining the value of Beta= Omega_m^{0.6}/b, where b is the galaxy bias parameter, is presented. In contrast to other existing techniques that focus on estimating this quantity by measuring distortions in the redshift space galaxy-galaxy correlation function or power spectrum, this method removes the distortions by reconstructing the real space density field and determining the value of Beta that results in a symmetric signal. To remove the distortions, the method modifies the amplitudes of a Fourier plane-wave expansion of the survey data parameterized by Beta. This technique is not dependent on the small-angle/plane-parallel approximation and can make full use of large redshift survey data. It has been tested using simulations with four different cosmologies and returns the value of Beta to +/- 0.031, over a factor of two improvement over existing techniques.Comment: 16 pages including 6 figures Submitted to The Astrophysical Journa

Snake (Colubridae: Thamnophis) Predatory Responses to Chemical Cues from Native and Introduced Prey Species

Several aquatic vertebrates have been introduced into freshwater systems in California over the past 100 years. Some populations of the two-striped garter snake (Thamnophis hammondii) have lived in sympatry with these species since their introduction; other populations have never encountered them. To assess the possible adaptation to a novel prey, we tested the predatory responses of T. hammondii from different populations to different chemosensory cues from native and introduced prey species. We presented chemical extracts from potential prey types and 2 control odors to individual snakes on cotton swabs and recorded the number of tongue flicks and attacks directed at each swab. Subject response was higher for prey odors than control substances. Odors from introduced centrarchid fish (Lepomis) elicited higher response levels than other prey types, including native anuran larvae (Pseudacris regilla). The pattern of response was similar for both populations of snakes (experienced and naïve, with respect to the introduced prey). We suggest that the generalist aquatic lifestyle of T. hammondii has allowed it to take advantage of increasing populations of introduced prey. Decisions on the management strategies for some of these introduced prey species should include consideration of how T. hammondii populations might respond in areas of sympatry

Four Health Care Organizations' Efforts to Improve Patient Care and Reduce Costs

Synthesizes findings from four case studies in the Brookings-Dartmouth ACO Pilot Program about forming integrated systems that can deliver accountable care under shared-savings agreements with private payers

Crossover and scaling in a two-dimensional field-tuned superconductor

Using an analysis similar to that of Imry and Wortis, it is shown that the apparent first order superconductor to metal transition, which has been claimed to exist at low values of the magnetic field in a two-dimensional field-tuned system at zero temperature,can be consistentlyinterpreted as a sharp crossover from a strong superconductor to an inhomogeneous state, which is a weak superconductor. The true zero-temperature superconductor to insulator transition within the inhomogenous state is conjectured to be that of randomly diluted XY model. An explaination of the observed finite temperature approximate scaling of resistivity close to the critical point is speculated within this model.Comment: 5 pages, 2 figures, corrected and modified according to referee Report