Green River Basin Research Articles

Influence of oil and gas field operations on spatial and temporal distributions of atmospheric non-methane hydrocarbons and their effect on ozone formation in winter

Abstract. Emissions from oil and natural gas development during winter in the Upper Green River basin of Wyoming are known to drive episodic ozone (O3) production. Contrasting O3 distributions were observed in the winters of 2011 and 2012, with numerous episodes (hourly O3 ≥ 85 ppbv) in 2011 compared to none in 2012. The lack of O3 episodes in 2012 coincided with a reduction in measured ambient levels of total non-methane hydrocarbons (NMHC). Measurements of speciated NMHC, and other air quality parameters, were performed to better understand emission sources and to determine which compounds are most active in promoting O3 formation. Positive matrix factorization (PMF) analyses of the data were carried out to help achieve these goals. PMF analyses revealed three contributing factors that were identified with different emission source types: factor 1, combustion/traffic; factor 2, fugitive natural gas; and factor 3, fugitive condensate. Compositional signatures of the three contributing factors were identified through comparison with independently derived emission source profiles. Fugitive emissions of natural gas and of condensate were the two principal emission source types for NMHC. A water treatment and recycling facility was found to be a significant source of NMHC that are abundant in condensate, in particular toluene and m+p-xylene. Emissions from water treatment have an influence upon peak O3 mixing ratios at downwind measurement sites.

New specimens and neotype designation ofThisbemys brevicrista(Rodentia, Ischyromyidae) from the middle Eocene clarify the distinction betweenT. corrugatusandT. plicatus

AbstractNewly discovered mandibles and lower dentition of the middle Eocene rodentThisbemys brevicristafrom the Green River Basin, Wyoming, are the basis for a species re-diagnosis. Previously, only the upper dentition and a partial maxilla ofT. brevicristawere known from Br3. New specimens from Br2 now include the lower molars, additional upper molars, and maxillary fragments including a partial zygomatic arch that preserves the relationship of the arch to the first upper molar. In addition, the presence ofT. brevicristaat Br2 documents the co-existence ofT. brevicristawithT. perditus, T. nini, T. plicatus,andT. corrugatus. Formerly, the latter two species were differentiated primarily using stratigraphy. Now, morphology and size can also be used.Thisbemys brevicristais intermediate in size betweenT. plicatusandT. corrugatus, and can readily be distinguished from these species based on unique features of the upper and lower molars, which include an additional loph on the two anterior upper molars and a complete metalophid on m1-3. The original type specimen ofT. brevicristaappears to be lost, thus a neotype is designated as part of the re-diagnosis. Discovery and description of the lower dentition and mandibles ofT. brevicristaclarifies the alpha taxonomy of this species, and increases its utility for studies of phylogenetic relationships and for documenting Eocene mammalian diversity patterns.

Late Laramide tectonic fragmentation of the eastern greater Green River Basin, Wyoming

Today9s greater Green River Basin is limited to the southwestern quarter of Wyoming. From late in the Cretaceous into late Paleocene time, however, sedimentary accumulations within that basin continued uninterruptedly much farther to the east, connecting areas now occupied by the isolated Hanna, Carbon, Pass Creek, and Laramie basins. Field-based research resulted in three contiguous geologic maps that focus on modern basin margins and boundaries among those eastern elements. Analyses of derived cross sections and restored stratigraphic columns suggest that active subsidence and rapid sedimentary accumulation persisted with only minor interruptions until very late in the Laramide Orogeny. That led to a generally symmetrical north–south cross-sectional configuration of the original Hanna Basin, with its true depositional axis set well south of its apparent position of today. The Hanna Basin9s present strong asymmetry developed only secondarily. That basin9s modern configuration reflects Paleogene influences of: (1) late Laramide (early Eocene and probably younger) basement-involved contractional tectonics and associated uplifts; (2) out-of-the-basin thrusting passively responding to stratigraphic crowding; (3) prodigious syntectonic erosion; and (4) resulting basin fragmentation. North–south dimension of the late Paleocene (i.e., pre-fragmentation) greater Hanna Basin sedimentary sequence was roughly twice that of today, and near-sea-level topographic conditions persisted until late Eocene time. As expected, remnants of basin margins universally show major thinning of stratigraphic sequences. Principal thinning was from tectonic causes, however, exhibiting erosional angular unconformities only rarely. Out-of-the-basin, younger-on-older faulting (in which fault planes cut down-section) accompanied by massive erosion was the rule at all basin margins. Uplift of Simpson Ridge Anticline postdated deposition of upper Paleocene strata in direct continuity between what is now the separated Hanna and Carbon basins. The basement-involved fault system responsible for westward relative tectonic transport (and ca. 8 km of elevation) by Simpson Ridge also led to raising the attached Carbon Basin. Original Hanna Formation of the Carbon Basin was beveled away by erosion and soon thereafter became replaced by shallow-slope sliding of a long-runout allochthon, the Carbon Basin Klippe. The klippe9s original site of deposition probably was to the northeast, above what later became Flat Top Anticline. Uplift of Flat Top and Simpson Ridge anticlines was essentially synchronous (latest Paleocene or, more probably, early Eocene), establishing a lengthy, faulted-synclinal separation of the Hanna/Carbon Basin from the Laramie Basin. That syncline also bifurcated Simpson Ridge Anticline into western and eastern segments. A second allochthon, the Dana Klippe, rests upon southern parts of the Hanna Syncline (of Hanna Basin). That klippe9s site of deposition probably was above the area that later elevated as Elk Mountain, thus causing origin of Pass Creek Basin. Elk Mountain9s ca. 12 km uplift could not have occurred prior to the early Eocene, and that event contributed to tight folding of the Hanna Syncline. Coal Bank Basin is a giant footwall syncline ahead of the out-of-the-basin, thrust-faulted (with relative tectonic transport to the southwest) Dana Ridge Anticline. That fault–fold complex represents a common structural style seen at all scales across the Hanna Basin.

Distributions of air pollutants associated with oil and natural gas development measured in the Upper Green River Basin of Wyoming

Abstract Diffusive sampler monitoring techniques were employed during wintertime studies from 2009 to 2012 to assess the spatial distribution of air pollutants associated with the Pinedale Anticline and Jonah Field oil and natural gas (O&NG) developments in the Upper Green River Basin, Wyoming. Diffusive sampling identified both the extent of wintertime ozone (O3) episodes and the distributions of oxides of nitrogen (NOx), and a suite of 13 C5+ volatile organic compounds (VOC), including BTEX (benzene, toluene, ethylbenzene and xylene isomers), allowing the influence of different O&NG emission sources to be determined. Concentration isopleth mapping of both diffusive sampler and continuous O3 measurements show the importance of localized production and advective transport. As for O3, BTEX and NOx mixing ratios within O&NG development areas were elevated compared to background levels, with localized hotspots also evident. One BTEX hotspot was related to an area with intensive production activities, while a second was located in an area influenced by emissions from a water treatment and recycling facility. Contrastingly, NOx hotspots were at major road intersections with relatively high traffic flows, indicating influence from vehicular emissions. Comparisons of observed selected VOC species ratios at a roadside site in the town of Pinedale with those measured in O&NG development areas show that traffic emissions contribute minimally to VOCs in these latter areas. The spatial distributions of pollutant concentrations identified by diffusive sampling techniques have potential utility for validation of emission inventories that are combined with air quality modeling.

The Use of Snow-Level Observations Derived from Vertically Profiling Radars to Assess Hydrometeorological Characteristics and Forecasts over Washington’s Green River Basin

Abstract Two vertically pointing S-band radars (coastal and inland) were operated in western Washington during two winters to monitor brightband snow-level altitudes. Similar snow-level characteristics existed at both sites, although the inland site exhibited lower snow levels by ~70 m because of proximity to cold continental air, and snow-level altitude changes were delayed there by several hours owing to onshore translation of weather systems. The largest precipitation accumulations and rates occurred when the snow level was largely higher than the adjacent terrain. A comparison of these observations with long-term operational radiosonde data reveals that the radar snow levels mirrored climatological conditions. The inland radar data were used to assess the performance of nearby operational freezing-level forecasts. The forecasts possessed a lower-than-observed bias of 100–250 m because of a combination of forecast error and imperfect representativeness between the forecast and observing points. These forecast discrepancies increased in magnitude with higher observed freezing levels, thus representing the hydrologically impactful situations where a greater fraction of mountain basins receive rain rather than snow and generate more runoff than anticipated. Vertical directional wind shear calculations derived from wind-profiler data, and concurrent surface temperature data, reveal that most snow-level forecast discrepancies occurred with warm advection aloft and low-level cold advection through the Stampede Gap. With warm advection, forecasts were too high (low) for observed snow levels below (above) 1.25 km MSL. An analysis of sea level pressure differences across the Cascades indicated that mean forecasts were too high (low) for observed snow levels below (above) 1.25 km MSL when higher pressure was west (east) of the range.

GIS and Artificial Neural Network–Based Water Quality Model for a Stream Network in the Upper Green River Basin, Kentucky, USA

AbstractThe prediction of stream water quality (WQ) is essential to understand and quantitatively describe water quality parameters (which include physical characteristics, inorganic metallic, and nonmetallic concentrations) and their structure, watershed health, biodiversity, and ecology of a basin. The spatial variability and temporal randomness of stream water quality parameters makes the problem a complex modeling task by ordinary statistical regression methods. The determination of water quality parameters and their spatial and temporal description in stream networks is even more complex due to the stochastic nature of water flow, atmospheric conditions, meteorological patterns, and nonlocal effects of precipitation and temperature. In this paper, a statistical, geographic information system (GIS) and a neural network based water quality model is developed to study stream water quality parameter structure in a geographic framework in the United States of America (USA) consisting of stream network, wa...

Conserving migratory mule deer through the umbrella of sage‐grouse

Conserving migratory ungulates in increasingly human‐dominated landscapes presents a difficult challenge to land managers and conservation practitioners. Nevertheless, ungulates may receive ancillary benefits from conservation actions designed to protect species of greater conservation priority where their ranges are sympatric. Greater Sage‐Grouse (Centrocerus urophasianus), for example, have been proposed as an umbrella species for other sagebrush (Artemesia spp.)‐dependent fauna. We examined a landscape where conservation efforts for sage‐grouse overlap spatially with mule deer (Odocoileus hemionus) to determine whether sage‐grouse conservation measures also might protect important mule deer migration routes and seasonal ranges. We conducted a spatial analysis to determine what proportion of migration routes, stopover areas, and winter ranges used by mule deer were located in areas managed for sage‐grouse conservation. Conservation measures overlapped with 66–70% of migration corridors, 74–75% of stopovers, and 52–91% of wintering areas for two mule deer populations in the upper Green River Basin of Wyoming. Of those proportions, conservation actions targeted towards sage‐grouse accounted for approximately half of the overlap in corridors and stopover areas, and nearly all overlap on winter ranges, indicating that sage‐grouse conservation efforts represent an important step in conserving migratory mule deer. Conservation of migratory species presents unique challenges because although overlap with conserved lands may be high, connectivity of the entire route must be maintained as barriers to movement anywhere within the migration corridor could render it unviable. Where mule deer habitats overlap with sage‐grouse core areas, our results indicate that increased protection is afforded to winter ranges and migration routes within the umbrella of sage‐grouse conservation, but this protection is contingent on concentrated developments within core areas not intersecting with high‐priority stopovers or corridors, and that the policy in turn does not encourage development on deer ranges outside of core areas. With the goal of protecting entire migration routes, our analysis highlights areas of potential conservation focus for mule deer, which are characterized by high exposure to residential development and use by a large proportion of migrating deer.

Strong wintertime ozone events in the Upper Green River basin, Wyoming

Abstract. During recent years, elevated ozone (O3) values have been observed repeatedly in the Upper Green River basin (UGRB), Wyoming, during wintertime. This paper presents an analysis of high ozone days in late winter 2011 (1 h average up to 166 ppbv – parts per billion by volume). Intensive operational periods (IOPs) of ambient monitoring were performed, which included comprehensive surface and boundary layer measurements. On IOP days, maximum O3 values are restricted to a very shallow surface layer. Low wind speeds in combination with low mixing layer heights (~ 50 m above ground level around noontime) are essential for accumulation of pollutants within the UGRB. Air masses contain substantial amounts of reactive nitrogen (NOx) and non-methane hydrocarbons (NMHC) emitted from fossil fuel exploration activities in the Pinedale Anticline. On IOP days particularly in the morning hours, reactive nitrogen (up to 69%), aromatics and alkanes (~ 10–15%; mostly ethane and propane) are major contributors to the hydroxyl (OH) reactivity. Measurements at the Boulder monitoring site during these time periods under SW wind flow conditions show the lowest NMHC / NOx ratios (~ 50), reflecting a relatively low reactive NMHC mixture, and a change from a NOx-limited regime towards a NMHC-limited regime as indicated by photochemical indicators, e.g., O3 /NOy, O3 /NOz, and O3 / HNO3 and the EOR (extent of reaction). OH production on IOP days is mainly due to nitrous acid (HONO). On a 24 h basis and as determined for a measurement height of 1.80 m above the surface HONO photolysis on IOP days can contribute ~ 83% to OH production on average, followed by alkene ozonolysis (~ 9%). Photolysis by ozone and HCHO photolysis contribute about 4% each to hydroxyl formation. High HONO levels (maximum hourly median on IOP days: 1096 pptv – parts per trillion by volume) are favored by a combination of shallow boundary layer conditions and enhanced photolysis rates due to the high albedo of the snow surface. HONO is most likely formed through (i) abundant nitric acid (HNO3) produced in atmospheric oxidation of NOx, deposited onto the snow surface and undergoing photo-enhanced heterogeneous conversion to HONO (estimated HONO production: 10.2 ± 40% ppbv h−1) and (ii) combustion-related emission of HONO (estimated HONO production: ~ 0.1 ± 30% ppbv h−1). HONO production is confined to the lowermost 10 m of the boundary layer. HONO, serves as the most important precursor for OH, strongly enhanced due to the high albedo of the snow cover (HONO photolysis rate 10.7 ± 30% ppbv h−1). OH radicals will oxidize NMHCs, mostly aromatics (toluene, xylenes) and alkanes (ethane, propane), eventually leading to an increase in ozone.

Anatomy of wintertime ozone associated with oil and natural gas extraction activity in Wyoming and Utah

Abstract Winter maximum daily 8-hour average (MDA8) ozone concentrations in the Upper Green River Basin, Wyoming (UGRBWY) and the Uintah Basin, Utah (UBUT) have frequently exceeded 100 ppb in January, February and March, in the past few years. Such levels are well above the U.S. air quality standard of 75 ppb. In these two remote basins in the Rockies, local ozone precursor emissions result from intense oil and gas extraction activities that release methane, volatile organic compounds (VOCs), and nitrogen oxides (NOx) to the atmosphere. These emissions become trapped beneath a stable and shallow (∼50–200 m) boundary layer maintained in low wind conditions. Wintertime surface ozone formation conditions are more likely in the UBUT than in the UGRBWY as the topography of the UBUT is an enclosed basin whereas the UGRBWY is open on its southern perimeter thus allowing for more air turnover. With snow-covered ground, high ozone events regularly begin in mid-December and last into early March in the UBUT whereas they usually do not begin in earnest until about a month later in the UGRBWY and may persist until mid-March. Winters without snow cover and the accompanying cold pool meteorological conditions do not experience high ozone events in either basin. For nine years with ozone observations in the UGRBWY (2005–2013) and four in the UBUT (2010–2013), all years with adequate (≥6 inches) and persistent snow cover, experienced days with ozone values ≥75 ppb except in 2012 in the UGRBWY when persistent high wind (>5 m/s) conditions were prevalent. Year to year differences in the occurrences of high ozone episodes appear to be driven primarily by differing meteorological conditions rather than by variations in ozone precursor levels.

English

A database framework was constructed with the purpose of creating a restoration decision management tool by compiling oil and gas pad reclamation data to identify successful restoration practices. Pre-existing data were secured from public and private databases from two Wyoming production fields in the Greater Green River Basin: Jonah Infill and Moxa Arch. The framework includes tables for measurements of reclamation practices (e.g., soil handling methods and amendments, seeding mix and timing, and weed management), geographical and climate data (e.g., precipitation, slope, aspect, elevation, and temperature) and monitoring data (e.g., vegetation composition and structure along with soil analysis and grazing). Microsoft Access and ESRI ArcGIS were employed to build the reclamation database for consistent and reliable data storage, manipulation, and retrieval. Short-term goals of the project were to quantify disturbance and reclamation efforts and to evaluate the reclamation status of individual well pads. Long-term goals of the project are to deliver: (1) an operational framework to analyze and isolate trends leading to reclamation success and failure, (2) a strong decision management tool for limiting uncertainty and estimating associated risk under variable environmental conditions, (3) to evaluate regulatory standards for reclamation, and (4) to offer a flexible and sharable database that allows for additional data input from diverse sources. Database performance was found to be dependent on data consistency and validity. Querying populated data along with uniting imported data has revealed multiple strengths and weaknesses with the database framework. Additional

Lithic Sources in Wyoming's Upper Green River Basin

Chert, quartzite, and steatite source areas have been documented in the Upper Green River Basin of western Wyoming. Riparian processes and glacial action have transported materials and modified the distributions of some deposits, producing a range of primary ( in situ geological strata) and secondary (re-deposited) source areas that were popular at different times. The results of characterization methods used to identify local and non-local (e.g., obsidian and ignimbrite) lithic raw materials in the region are summarized in order to discuss native mobility, exchange, social interaction, and resistance strategies to colonization.

Statistical analysis of winter ozone events

We have developed quadratic regression models that predict the daily ozone concentration in either the Uintah Basin (UB) of Utah, USA, or the Upper Green River Basin (UGRB) of Wyoming, USA. Sites selected for study are ozone stations near the towns of Ouray, Utah, in the UB and Boulder, Wyoming, in the UGRB. Input data for the UB model are daily values of lapse rate, snow depth, solar angle, temperature, and the number of consecutive days under inversion conditions. The UGRB model also requires the wind speed. Standard errors are 10 and 5 ppb for the UB and the UGRB, respectively. The models have been optimized to predict seasonal exceedances of the National Ambient Air Quality Standard (NAAQS), i.e., the number of times each season that the daily maximum in the eight-hour running average exceeds 75 ppb, and they perform in this regard to an accuracy of ±1 day. (However, Ouray is not at this time a regulatory site for judging compliance with federal law.) We predict that any given winter will be NAAQS compliant with 44 % odds in the UB and with 60 % odds in the UGRB. We have estimated the ozone production for each winter in the UB since 1950, under the assumption that precursor emissions are at modern values.

Experimental study of shortite (Na2Ca2(CO3)3) formation and application to the burial history of the Wilkins Peak Member, Green River Basin, Wyoming, USA

The temperature at which shortite (Na2Ca2(CO3)3) forms from pirssonite (Na2Ca(CO3)2·2H2O) and calcite using pure synthetic phases in the system Na2CO3–CaCO3–H2O has been experimentally determined. At ∼1atm pressure, shortite forms via the reaction Na2Ca(CO3)2·2H2O+CaCO3=Na2Ca2(CO3)3+2H2O above 55±2°C. This equilibrium temperature is lower than determined previously (90±25°C) by Bradley and Eugster (1969). The solution in equilibrium with synthetic shortite, pirssonite, and calcite approximates a binary H2O–Na2CO3 brine with 1.1m Na2CO3 (10.6wt% Na2CO3). The equilibrium temperature is lowered to 52±2°C with 5m NaCl added to the system, which shows that this reaction is weakly dependent on the activity of H2O, aH2O. This study suggests that shortite does not occur in surficial alkaline saline environments because temperatures are too low.Shortite is abundant in the Wilkins Peak Member (WPM) of the Eocene Green River Formation, Green River Basin, Wyoming, USA (>78million tons/km2), where it occurs as diagenetic displacive crystals, fracture fills, and pseudomorphous replacements of a precursor Na–Ca–carbonate. The large area over which shortite occurs in the WPM indicates that saline pore fluids once existed in the buried lacustrine sediments, and thus, at times, large Na–CO3-rich saline alkaline lakes or laterally extensive saline groundwaters existed in the Green River Basin during WPM time. The thermal stability of shortite, together with vitrinite reflectance data and inferred regional geothermal gradients, establish that the shortite-bearing intervals of the WPM were buried to maximum depths of ∼1000m in the Green River Basin, and since experienced ∼800m of erosional exhumation.

Eocene extension in Idaho generated massive sediment floods into the Franciscan trench and into the Tyee, Great Valley, and Green River basins

The Franciscan Complex accretionary prism was assembled during an ~165-m.y.-long period of subduction of Pacifi c Ocean plates beneath the western margin of the North American plate. In such fossil subduction complexes, it is generally diffi cult to reconstruct details of the accretion of continent-derived sediments and to evaluate the factors that controlled accretion. New detrital zircon U-Pb ages indicate that much of the major Coastal belt subunit of the Franciscan Complex represents a massive, relatively brief, surge of near-trench deposition and accretion during Eocene time (ca. 53‐49 Ma). Sediments were sourced mainly from the distant Idaho Batholith region rather than the nearby Sierra Nevada. Idaho detritus also fed the Great Valley forearc basin of California (ca. 53‐37 Ma), the Tyee forearc basin of coastal Oregon (49 to ca. 36 Ma), and the greater Green River lake basin of Wyoming (50‐47 Ma). Plutonism in the Idaho Batholith spanned 98‐53 Ma in a contractional setting; it was abruptly superseded by major extension in the Bitterroot, Anaconda, Clearwater, and Priest River metamorphic core complexes (53‐40 Ma) and by major volcanism in the Challis volcanic fi eld (51‐43 Ma). This extensional tectonism apparently deformed and uplifted a broad region, shedding voluminous sediments toward depocenters to the west and southeast. In the Franciscan Coastal belt, the major increase in sediment input apparently triggered a pulse of massive accretion, a pulse ultimately controlled by continental tectonism far within the interior of the North American plate, rather than by some tectonic event along the plate boundary itself.

Eocene extension in Idaho generated massive sediment floods into the Franciscan trench and into the Tyee, Great Valley, and Green River basins

Eocene extension in Idaho generated massive sediment floods into the Franciscan trench and into the Tyee, Great Valley, and Green River basins

Taxonomic Clarification and Phylogeography ofFluminicola coloradensisMorrison, a Widely Ranging Western North American Pebblesnail

Herein we clarify the taxonomy of Fluminicola coloradensis Morrison (1940), which was described for populations in the Green River and Bonneville basins but has also been treated as restricted to the former watershed and conspecific with (currently unassigned) Snake River basin populations of Fluminicola hindsi sensu Taylor (1966). Bayesian analyses of DNA sequences from 2 mitochondrial genes congruently resolved F. coloradensis and Snake River basin populations of F. hindsi sensu Taylor as a strongly supported, shallowly structured clade. Haplotypes were extensively shared by Bonneville, Snake River and Green River populations; AMOVA did not detect significant variation among basins for either gene. Morphological variation was minor. Based on these results, we assign the Snake River basin populations to F. coloradensis. We attribute the limited differentiation of widely ranging F. coloradensis to its well-integrated habitats and to dispersal mediated by geologically recent drainage transfers. The broadly disjunct population in the Owyhee River drainage may be a product of translocation, as evidenced by detection of only the most common haplotypes in these snails. Our finding that F. coloradensis is more widely distributed than previously thought suggests that it may not require conservation attention rangewide, although some geographic subunits may be at risk.

Denudation and flexural isostatic response of the Colorado Plateau and southern Rocky Mountains region since 10 Ma

Over the past 10 Ma, the high-relief landscapes of the Colorado Plateau–southern Rocky Mountains region have been shaped by erosional processes. Incision rates have increased in the southern Rocky Mountains, the Colorado River system has been superimposed across buried Laramide structures as it was integrated from the Rocky Mountains to the Gulf of California, the modern Grand Canyon formed, and there has been widespread denudation of the Canyonlands region of the Colorado Plateau. We examine the spatial and temporal distribution of erosion and its associated isostatic rebound since 10 Ma. Erosion estimates come from apatite fission track (AFT) and apatite (U-Th)/He (AHe) thermochronometric studies at 14 sites across the region, including recent AHe data with ages younger than 12 Ma, and from ca. 10 Ma 40 Ar/ 39 Ar dated basalt paleosurfaces at 55 locations on the perimeter of the Colorado Plateau and in the southern Rocky Mountains. Estimated eroded thickness is added to modern topography above numerous control points to reconstruct a 10 Ma paleosurface across the region (referenced to modern elevations); this also yields an eroded thickness volume. Erosion has been spatially variable since 10 Ma: we find widespread denudation with as much as 2 km of incision along rivers in the Canyonlands region of Utah, 1–1.5 km of incision along rivers exiting the Rocky Mountains onto the eastern piedmont since 6 Ma, ∼1 km removed across the high peaks of the southern Rocky Mountains since 10 Ma, and little net erosion in the Basin and Range. Post–10 Ma flexural isostatic response to the eroded volume is calculated using known variable elastic thickness. This rebound caused much of the Colorado Plateau region to undergo more than 800 m of rock uplift, exceeding 1 km in local areas in the Canyonlands and southwestern Colorado. The Lees Ferry and Glen Canyon areas have been isostatically uplifted >500 m relative to the eastern Grand Canyon and the Tavaputs Plateau has been isostatically uplifted 400 m relative to Browns Park. This differential rock uplift driven by erosional isostasy has created or accentuated many of the features of the modern landscape. This component of rock uplift is “removed” by adding the eroded thickness onto modern topography, then subtracting the calculated rebound. The resulting (pre-erosion and pre-rebound) map provides a model of the 10 Ma landscape, neglecting any tectonic uplift contribution to regional elevations. This model suggests the presence of internal drainages on the Colorado Plateau, that the elevation of the Green River Basin and the Tavaputs Plateau were subequivalent, allowing the Green River to flow southward, and shows high topography in the Rocky Mountains that mimicked modern topography, but with potentially lower relief. Future refinements of both the timing and magnitude of differential erosion and rebound models provide an avenue for improved models for Cenozoic landscape evolution of the region. This paper is an advance over previous studies that focused just on the Colorado Plateau. Here we evaluate isostatic response to erosion in an extended region that includes parts of the Basin and Range, Colorado Plateau, southern Rocky Mountains, and eastern piedmont of the Rocky Mountains. We find that erosion of the southern Rocky Mountains and eastern piedmont is comparable to that of the Colorado Plateau and that the flexural isostatic rebounds of all these regions are coupled and cannot be considered in isolation. Furthermore, we focus on the 10 Ma time frame, rather than the 30 or 70 Ma period of previous researchers, as the key time frame during which the modern landscape rapidly evolved. In addition, the use of AFT and AHe thermochronometric constraints on thicknesses and ages of now-eroded sediments has solved key problems that hampered previous erosion studies. Data and analyses of regional post–10 Ma differential erosion and its resulting differential isostatic rebound provide essential constraints for any viable models for landscape evolution in this classic region.

Characterizations of the CCUS Attributes of a High-priority CO2 Storage Site in Wyoming, USA

Optimizing uncertainty reduction in evaluations of geological CO2 storage site scenarios requires a robust database that allows an accurate reconstruction of the targeted storage rock/fluid volume, especially with respect to spatial heterogeneity. Previous numerical simulations of the Rock Springs Uplift site (southwest Wyoming, USA) relied on a generalized regional database to populate a homogenous rock/fluid volume based on average reservoir properties. The results from this approach yielded general insights into injection/storage characteristics but lacked specificity, resulting in performance assessments plagued by substantial uncertainty. To move from idealistic, highly generalized assessments to realistic, low-risk assessments of the Rock Springs Uplift, it was necessary to acquire high-resolution data specific to the storage site of interest (carbonate and sandstone reservoirs, and confining layers in an 8km × 8km area). The foundation of the new database is a 4,000-meter-deep stratigraphic test well, an 8km × 8km 3-D seismic survey, 290 meters of high-quality core, a specialized log suite, fluid samples, and a diverse set of analytical laboratory measurements. These data made it possible to correlate seismic attributes with observations from log suites, a VSP survey, core, fluid samples, and laboratory analyses, including continuous permeability scans. From seismic data, 3-D spatial distribution volumes of reservoir and confining layer properties were constructed that represent geological heterogeneity at the targeted CO2 storage site. Consequently, the latest numerical simulations and performance assessments are characterized by substantially lower geological uncertainties.The new CO2 plume migration simulations for a set of defined CO2 injection rates and volumes occupy larger rock/fluid volumes and display pronounced marginal irregularities when compared to early simulations derived from homogenous reservoir parameter volumes. The spatial distributions of the injected CO2 plumes in previous simulations are conical with few marginal irregularities, whereas in the new simulations, the CO2 plumes occupy a larger up-dip volume and display pronounced marginal irregularities. These irregularities denote zones of higher porosity and permeability, such as collapsed breccias associated with karst zones and/or dolomitized grainstone zones in the Madison Limestone.Using the new numerical simulations which include heterogeneous rock/fluid parameter distributions, it is apparent that in all injection/storage scenarios of > 1 Mt/year CO2, substantial displaced fluid production/treatment is essential to manage pressure and maintain the integrity of confining layers. The total dissolved solids concentrations of the formation fluids retrieved from the Madison Limestone range from 80,000 to 90,000ppm, and will necessitate customized water treatment strategies and facilities at the surface. The new data and upgraded evaluations demonstrate that the Rock Springs Uplift in southwestern Wyoming remains an outstanding large-scale geological CO2 storage site, and provides a realistic basis for designing commercial CO2 injection/storage operations on the Uplift.The 2010 U.S. Environmental Protection Agency Greenhouse Gas Reporting Program reports that in the Greater Green River Basin of southwest Wyoming, the CO2 emissions from stationary sources (sources that emit more than 25,000 tons of CO2 per year) total 29+ million tons annually, or approximately 50 percent of Wyoming's annual CO2 emissions. These CO2 sources include coal-fired power plants, gas and trona processing plants, pipeline compression stations, chemical production facilities, and gas-field complexes, among others. The Rock Springs Uplift in the center of the Greater Green River Basin is ideally located to serve as a large-scale commercial geological CO2 storage facility for half of all of Wyoming's industrial CO2 emissions. The new numerical simulations suggest that the Madison Limestone has the ability to permanently store the annual CO2 emissions from stationary sources in the Greater Green River Basin for 130 years (i.e., a total of 3.8 billion tons). The overlying Paleozoic Weber Sandstone on the Rock Springs Uplift has additional commercial-scale CO2 storage capacity.The Rock Springs Uplift has the attributes to serve as a regional CO2 storage site, and importantly, this site could be used as a storage/surge tank to supply CO2 to EOR projects throughout Wyoming.

Lowered Tubing Offsets Field Production Decline

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 154394, ’Lowering Tubing in the Jonah Field Offsets Production Decline,’ by Chinenye E. Ogugbue, SPE, Cody R. Hopkins, Leah R. Greenly, SPE, Robert K. Wilson, and Gordon E. Gates, BP, prepared for the 2012 Americas Unconventional Resources Conference, Pittsburgh, Pennsylvania, 5-7 June. The paper has not been peer reviewed. Declining reservoir pressure and rate in the Jonah Field in the upper Green River basin in west-central Wyoming led to the common problem of liquid loading. Lowering the end of tubing (EOT) in more than 100 gas wells in the Jonah field enabled an average sustained production increase of approximately 105 Mcf/D, with an undiscounted payout of less than 12 months. In addition, for wells that have had the tubing lowered, the production-decline curves appeared to flatten out, offsetting anticipated double-digit decline. Introduction Discovered in the early 1990s, the Jonah field produces gas from the Lance formation, an extremely low-porosity, low-permeability, and fine-grained alluvial sandstone. The field is an overpressured area bounded on west and south by faults. The producing-formation thickness ranges from 2,000 ft updip to 3,500 ft downdip, at depths as shallow as 7,800 ft and as deep as 12,500 ft. Within this interval, the net-to gross-pay ratio varies from 25 to 40%. Sand bodies occur as both individual 9- to 15-ft-thick channels and as stacked-channel sequences, thicker than 200 ft in some places. Stacking of these alluvial-sand bodies resulted in an extremely heterogeneous reservoir in which reservoir sand bodies cover an areal extent of a few acres to as much as 640 acres. The field has been developed on 10-acre spacing. Wells are completed with eight to 16 hydraulic-fracturing stages, with each stage containing five to seven fluvial-sand-body channels. The Lance formation comprises the Lance Derbis Wedge, Lance Overpressure, Middle Lance, Jonah sands (Lance Jonah), Yellow Point sands, and the Wardell sands. The proven commercial gas-producing zones are the Lance Overpressure through the Wardell. BP operates 262 wells in the Jonah field. The wells have total depths ranging from 10,500 to 12,800 ft, with an approximately 3,500-ft vertical section of thick continental deposit composed of fluvial sandstones, back-swamp shales, coaly shales, and thick braided-stream sandstones. Porosity ranges from 8 to 10%, with permeability equal to 1 to 10 d. The average initial 30-day production was 1.5 MMcf/D. The aver-age condensate yield is 8.5 bbl/MMcf, and the water yield is 5–10 BW/MMcf.

Coupled CO2-climate response during the Early Eocene Climatic Optimum

The Early Eocene Climatic Optimum (EECO) has been characterized as a prolonged warm event indicated by increased atmospheric pCO2, temperatures, precipitation, and biological turnover. A new paleoenvironmental reconstruction using integrated pedological, geochemical, and isotopic data from the Green River Basin (Green River/Great Divide region) provides a high-resolution record of environmental and climatic change throughout the EECO. Our reconstruction indicates that this region, and likely much of the margin of paleolake Gosiute, was a stable, fluvially-controlled floodplain environment with evidence of large scale continuous soil development and features comparable with modern Alfisols (temperate forest soils). Regional climate data from multiple proxies indicates that the period was warm-temperate and semi-arid to sub-humid, with a peak interval from about 51.5–50.9Ma that exhibits significantly warmer (~7°C) and wetter (~750mmyr−1) conditions, resulting in major changes to the local weathering regime. Isotopic analyses also indicate a rapid increase to high atmospheric pCO2 values (~1700ppmV) and a shift in the δ13C composition of pedogenic carbonates during this peak interval that appear to define and provide a cause for this significant regional response to global climatic change. The new data, when combined with foraminiferal δ13C records, are consistent with CO2 ventilation from a deep marine reservoir source. This multi-proxy reconstruction suggests that the EECO may have had a superimposed “peak” of climatic and ecological change on land.