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At least 343 records · Page 19Linked to original sources

USGS1997

Detecting changes in the spatial distribution of nitrate contamination in ground water

Many studies of ground water pollution in general and nitrate contamination in particular have often relied on a one-time investigation, tracking of individual wells, or aggregate summaries. Studies of changes in spatial distribution of contaminants over time are lacking. This paper presents a method to compare spatial distributions for possible changes over time. The large-scale spatial distribution at a given time can be considered as a surface over the area (a trend surface). The changes in spatial distribution from period to period can be revealed by the differences in the shape and/or height of surfaces. If such a surface is described by a polynomial function, changes in surfaces can be detected by testing statistically for differences in their corresponding polynomial functions. This method was applied to nitrate concentration in a population of wells in an agricultural drainage basin in Iowa, sampled in three different years. For the period of 1981-1992, the large-scale spatial distribution of nitrate concentration did not show significant change in the shape of spatial surfaces; while the magnitude of nitrate concentration in the basin, or height of the computed surfaces showed significant fluctuations. The change in magnitude of nitrate concentration is closely related to climatic variations, especially in precipitation. The lack of change in the shape of spatial surfaces means that either the influence of land use/nitrogen management was overshadowed by climatic influence, or the changes in land use/management occurred in a random fashion.

Journal of the American Water Resources Associatio↗

USGS2016

Effects of land use and sample location on nitrate-stream flow hysteresis descriptors during storm events

The U.S. Geological Survey's New Jersey and Iowa Water Science Centers deployed ultraviolet-visible spectrophotometric sensors at water-quality monitoring sites on the Passaic and Pompton Rivers at Two Bridges, New Jersey, on Toms River at Toms River, New Jersey, and on the North Raccoon River near Jefferson, Iowa to continuously measure in-stream nitrate plus nitrite as nitrogen (NO 3 + NO 2 ) concentrations in conjunction with continuous stream flow measurements. Statistical analysis of NO 3 + NO 2 vs . stream discharge during storm events found statistically significant links between land use types and sampling site with the normalized area and rotational direction of NO 3 + NO 2 -stream discharge (N-Q) hysteresis patterns. Statistically significant relations were also found between the normalized area of a hysteresis pattern and several flow parameters as well as the normalized area adjusted for rotational direction and minimum NO 3 + NO 2 concentrations. The mean normalized hysteresis area for forested land use was smaller than that of urban and agricultural land uses. The hysteresis rotational direction of the agricultural land use was opposite of that of the urban and undeveloped land uses. An r 2 of 0.81 for the relation between the minimum normalized NO 3 + NO 2 concentration during a storm vs . the normalized NO 3 + NO 2 concentration at peak flow suggested that dilution was the dominant process controlling NO 3 + NO 2 concentrations over the course of most storm events.

Iowa, New Jersey↗

USGS2007

Multiple-methods investigation of recharge at a humid-region fractured rock site, Pennsylvania, USA

Lysimeter-percolate and well-hydrograph analyses were combined to evaluate recharge for the Masser Recharge Site (central Pennsylvania, USA). In humid regions, aquifer recharge through an unconfined low-porosity fractured-rock aquifer can cause large magnitude water-table fluctuations over short time scales. The unsaturated hydraulic characteristics of the subsurface porous media control the magnitude and timing of these fluctuations. Data from multiple sets of lysimeters at the site show a highly seasonal pattern of percolate and exhibit variability due to both installation factors and hydraulic property heterogeneity. Individual event analysis of well hydrograph data reveals the primary influences on water-table response, namely rainfall depth, rainfall intensity, and initial water-table depth. Spatial and seasonal variability in well response is also evident. A new approach for calculating recharge from continuous water-table elevation records using a master recession curve (MRC) is demonstrated. The recharge estimated by the MRC approach when assuming a constant specific yield is seasonal to a lesser degree than the recharge estimate resulting from the lysimeter analysis. Partial reconciliation of the two recharge estimates is achieved by considering a conceptual model of flow processes in the highly-heterogeneous underlying fractured porous medium.

Pennsylvania↗

USGS2024

Vortex trapping of suspended sand grains over ripples

Coastal hydrodynamics and morphodynamics integrate the effects of small-scale fluid-sediment interactions; yet, these small-scale processes are not well understood. To investigate sediment trapping by turbulent coherent structures or vortices, the transport of coarse sand over ripples was analyzed in a small-oscillatory flow tunnel with phase-separated Particle Image and Tracking Velocimetry. Results from one of the first direct measurements of vortex-trapped sand grains under oscillatory flows are presented. The vortices mobilized sand grains along the ripple slopes just prior to flow reversal and transported the suspended sediment grains. During several flow cycles, some sand grains were temporarily trapped in the vortex, prescribing semi-circular trajectories off-center from the vortex core in quadrants of the vortex that were closest to the ripple slope, as illustrated by Nielsen (1992, https://doi.org/10.1142/1269 ). Comparisons of the horizontal sediment grain velocity with the horizontal fluid velocity yielded a linear relationship with a slope of 0.87. The vertical grain velocities also varied linearly with the vertical fluid velocity with a slope of approximately 1 and an offset of −0.08 m s −1 . The offset is close to the still water settling velocity for coarse sand grains, as hypothesized during vortex trapping. Additionally, estimates of the off-center distance, between the centers of the semi-circular sediment paths and vortex cores, compared well with the ratio of the settling velocity to the radian frequency of the vortex yielding a linear regression slope of 0.99. Improved understanding of vortex trapping effects on sediment dynamics may decrease uncertainty in model predictions of large-scale coastal hydrodynamics and sediment transport.

Journal of Geophysical Research: Earth Surface↗

USGS2016

Emerging tools for continuous nutrient monitoring networks: Sensors advancing science and water resources protection

Sensors and enabling technologies are becoming increasingly important tools for water quality monitoring and associated water resource management decisions. In particular, nutrient sensors are of interest because of the well-known adverse effects of nutrient enrichment on coastal hypoxia, harmful algal blooms, and impacts to human health. Accurate and timely information on nutrient concentrations and loads is integral to strategies designed to minimize risk to humans and manage the underlying drivers of water quality impairment. Using nitrate sensors as an example, we highlight the types of applications in freshwater and coastal environments that are likely to benefit from continuous, real-time nutrient data. The concurrent emergence of new tools to integrate, manage and share large data sets is critical to the successful use of nutrient sensors and has made it possible for the field of continuous nutrient monitoring to rapidly move forward. We highlight several near-term opportunities for Federal agencies, as well as the broader scientific and management community, that will help accelerate sensor development, build and leverage sites within a national network, and develop open data standards and data management protocols that are key to realizing the benefits of a large-scale, integrated monitoring network. Investing in these opportunities will provide new information to guide management and policies designed to protect and restore our nation’s water resources.

Journal of the American Water Resources Associatio↗

USGS2013

Updated methodology for nuclear magnetic resonance characterization of shales

Unconventional petroleum resources, particularly in shales, are expected to play an increasingly important role in the world’s energy portfolio in the coming years. Nuclear magnetic resonance (NMR), particularly at low-field, provides important information in the evaluation of shale resources. Most of the low-field NMR analyses performed on shale samples rely heavily on standard T 1 and T 2 measurements. We present a new approach using solid echoes in the measurement of T 1 and T 1 –T 2 correlations that addresses some of the challenges encountered when making NMR measurements on shale samples compared to conventional reservoir rocks. Combining these techniques with standard T 1 and T 2 measurements provides a more complete assessment of the hydrogen-bearing constituents (e.g., bitumen, kerogen, clay-bound water) in shale samples. These methods are applied to immature and pyrolyzed oil shale samples to examine the solid and highly viscous organic phases present during the petroleum generation process. The solid echo measurements produce additional signal in the oil shale samples compared to the standard methodologies, indicating the presence of components undergoing homonuclear dipolar coupling. The results presented here include the first low-field NMR measurements performed on kerogen as well as detailed NMR analysis of highly viscous thermally generated bitumen present in pyrolyzed oil shale.

Journal of Magnetic Resonance↗

USGS2019

A fuzzy logic approach for estimating recovery factors of miscible CO2-EOR projects in the United States

"Recovery factor (RF) is one of the most fundamental parameters that define engineering and economical success of any operational phase in oil and gas production. The effectiveness of the operation, e.g. CO2-EOR (enhanced oil recovery with carbon dioxide injection), is usually defined by multiplying the resultant recovery factor by the original oil in place. Moreover, investment decisions for such engineering projects are also performed based on predicted recovery factors. Despite its importance, though, it is not easy to predict recovery factors as they are affected by many factors including the type of the recovery process, reservoir type, fluid properties, reservoir heterogeneity, depth, thickness, to name a few. The usual method of estimating recovery factors is laboratory experiments or numerical modeling, each of which has their own limitations due to data requirements, boundary conditions and scale effects. In this work, a fuzzy inference system approach has been adopted to predict miscible CO2-EOR recovery factors of the major field applications in the United States with the premise that it can be used as a guidance tool for making decisions based on different inputs. The fuzzy system was build using a Mamdani-type fuzzy logic inference engine, and by using reservoir data compiled from different sources as inputs and recovery factors gathered from a literature survey. Due to the limited number of field cases that could be used for this purpose, 24 sets of applications were included in the study. Selected input variables were water saturation after waterflood (Sorw), well spacing, porosity, permeability, depth, net pay thickness, initial pressure, API gravity of oil, hydrocarbon pore volume CO2 injected, and reservoir lithology. The type of membership functions were decided based on the system’s predictive performance. The model showed reasonable predictive capability for the field observations of recovery factor despite the complexity of this parameter. In addition, since the fuzzy solution was multi-dimensional due to multiple inputs, system behavior was used to demonstrate response of miscible CO2-EOR recovery factor to different inputs. "

Journal of Petroleum Science and Engineering↗

USGS2024

Will there be water? Climate change, housing needs, and future water demand in California

Climate change in California is expected to alter future water availability, impacting water supplies needed to support future housing growth and agriculture demand. In groundwater-dependent regions like California's Central Coast, new land-use related water demand and decreasing recharge is already stressing depleted groundwater basins. We developed a spatially explicit state-and-transition simulation model that integrates climate, land-use change, water demand, and groundwater gain-loss to examine the impact of future climate and land use change on groundwater balance and water demand in five counties along the Central Coast from 2010 to 2060. The model incorporated downscaled groundwater recharge projections based on a Warm/Wet and a Hot/Dry climate future from a spatially explicit hydrological process-based model. Two urbanization projections from a parcel-based, regional urban growth model representing 1) recent historical and 2) state-mandated housing growth projections were used as alternative spatial targets for future urban growth. Agricultural projections were based on recent historical trends from remote sensing data. Annual projected changes in groundwater balance were calculated as the difference between land-use related water demand, based on historical estimates, and climate-driven recharge plus agriculture return flows. Results indicate that future changes in climate-driven groundwater recharge, coupled with cumulative increases in agricultural water demand, result in overall declines in future groundwater balance, with a Hot/Dry future resulting in cumulative groundwater decline in all but Santa Cruz County. Cumulative declines by 2060 are especially prominent in San Luis Obispo (−2.9 to −5.1 Bm 3 ) and Monterey counties (−6.5 to −8.7 Bm 3 ), despite limited changes in agricultural water demand over the model period. These two counties show declining groundwater reserves in a Warm/Wet future as well, while San Benito and Santa Barbara County barely reach equilibrium. These results suggest future groundwater supplies may not be able to keep pace with regional demand and declining climate-driven recharge, resulting in a potential reduction in water security in the region. However, our county-scale projections showed new housing and associated water demand does not conflict with California's groundwater sustainability goals. Rather, future climate coupled with increasing agricultural groundwater demand may reduce water security in some counties, potentially limiting available groundwater supplies for new housing.

California↗

USGS2012

Reservoir processes and fluid origins in the Baca geothermal system, Valles Caldera, New Mexico

At the Baca geothermal field in the Valles caldera, New Mexico, 19 deep wells were drilled in an attempt to develop a 50-MW e (megawatts electric) power plant. The chemical and isotopic compositions of steam and water samples have been used to indicate uniquely the origin of reservoir fluids and natural reservoir processes. Two distinct reservoir fluids exist at Baca. These fluids originate from the same deep, high-temperature (335°C), saline (2500 mg/kg Cl) parent water but have had different histories during upflow. One fluid (from wells 4 and 13) is isotopically light, high in radiogenic noble gases, CO 2 and HCO 3 , and low in Ca. It has a temperature of 290°–295°C and a reservoir chloride near 1900 mg/kg. This fluid resulted from rapid upward flow through 1.1- to 1.4-m.y.-old Bandelier Tuff reservoir rocks after long residence in pre-Bandelier (>7 m.y.) sediments and Precambrian basement rocks and 25% dilution with high-altitude cold groundwater from Redondo Peak. The other water (from wells 15, 19, and 24) moved slowly through the Bandelier Tuff and cooled conductively (with minor steam loss for well 19) from 335°C to 280°–260°C. Apparently, short residence in old basement rocks has left this water with low radiogenic gases. Conductive cooling without mixing has kept the original chloride and relatively heavy isotope composition of the deep water. The recharge to the deep parent water is not well understood but may be from lower elevation precipitation outside the Valles caldera area. Gases are in equilibrium in all-liquid reservoir fluids at near reservoir temperatures, and the concentrations of atmospheric gases are similar to those of air-saturated water, indicating little boiling and steam loss. All water, solutes, and gases in the reservoir fluids originate from air-saturated meteoric recharge water, watermineral reactions, and rock leaching, with the possible exception of excess 3He that must have an ultimate mantle source. This gas could originate directly from magma or from leaching of intrusive volcanic rocks beneath the Bandelier.

Journal of Geophysical Research Solid Earth↗

USGS2011

Demonstration of a conceptual model for using LiDAR to improve the estimation of floodwater mitigation potential of Prairie Pothole Region wetlands

Recent flood events in the Prairie Pothole Region of North America have stimulated interest in modeling water storage capacities of wetlands and their surrounding catchments to facilitate flood mitigation efforts. Accurate estimates of basin storage capacities have been hampered by a lack of high-resolution elevation data. In this paper, we developed a 0.5 m bare-earth model from Light Detection And Ranging (LiDAR) data and, in combination with National Wetlands Inventory data, delineated wetland catchments and their spilling points within a 196 km2 study area. We then calculated the maximum water storage capacity of individual basins and modeled the connectivity among these basins. When compared to field survey results, catchment and spilling point delineations from the LiDAR bare-earth model captured subtle landscape features very well. Of the 11 modeled spilling points, 10 matched field survey spilling points. The comparison between observed and modeled maximum water storage had an R 2 of 0.87 with mean absolute error of 5564 m 3 . Since maximum water storage capacity of basins does not translate into floodwater regulation capability, we further developed a Basin Floodwater Regulation Index. Based upon this index, the absolute and relative water that could be held by wetlands over a landscape could be modeled. This conceptual model of floodwater downstream contribution was demonstrated with water level data from 17 May 2008.

Journal of Hydrology↗

USGS2006

Determination of bromine, chlorine and iodine in environmental aqueous samples by epithermal neutron activation analysis and Compton suppression

Halides, particularly Br- and Cl-, have been used as indicators of potential sources of Na+ and Cl- in surface water and groundwater with limited success. Contamination of groundwater and surface water by Na+ and Cl- is a common occurrence in growing urban areas and adversely affects municipal and private water supplies in Illinois and other states, as well as vegetation in environmentally sensitive areas. Neutron activation analysis (NAA) can be effectively used to determine these halogens, but often the elevated concentrations of sodium and chlorine in water samples can give rise to very high detection limits for bromine and iodine due to elevated backgrounds from the activation process. We present a detailed analytical scheme to determine Cl, Br and I in aqueous samples with widely varying Na and Cl concentrations using epithermal NAA in conjunction with Compton suppression. ?? 2006 Akade??miai Kiado??.

Journal of Radioanalytical and Nuclear Chemistry↗

USGS2015

Changes in depth occupied by Great Lakes lake whitefish populations and the influence of survey design

Understanding fish habitat use is important in determining conditions that ultimately affect fish energetics, growth and reproduction. Great Lakes lake whitefish ( Coregonus clupeaformis ) have demonstrated dramatic changes in growth and life history traits since the appearance of dreissenid mussels in the Great Lakes, but the role of habitat occupancy in driving these changes is poorly understood. To better understand temporal changes in lake whitefish depth of capture ( D w ), we compiled a database of fishery-independent surveys representing multiple populations across all five Laurentian Great Lakes. By demonstrating the importance of survey design in estimating D w , we describe a novel method for detecting survey-based bias in D w and removing potentially biased data. Using unbiased D w estimates, we show clear differences in the pattern and timing of changes in lake whitefish D w between our reference sites (Lake Superior) and those that have experienced significant benthic food web changes (lakes Michigan, Huron, Erie and Ontario). Lake whitefish D w in Lake Superior tended to gradually shift to shallower waters, but changed rapidly in other locations coincident with dreissenid establishment and declines in Diporeia densities. Almost all lake whitefish populations that were exposed to dreissenids demonstrated deeper D w following benthic food web change, though a subset of these populations subsequently shifted to more shallow depths. In some cases in lakes Huron and Ontario, shifts towards more shallow D w are occurring well after documented Diporeia collapse, suggesting the role of other drivers such as habitat availability or reliance on alternative prey sources.

Lake Erie, Lake Huron, Lake Michigan, Lake Ontario↗

USGS1997

Modeling saltwater upconing in a freshwater aquifer in south-central Kansas

The Great Bend Prairie freshwater alluvial aquifer in south-central Kansas overlies a bedrock brine aquifer of Permian age. The continuous extraction of freshwater mainly for irrigation in this area has accelerated the upward movement of the saltwater, resulting in the deterioration of water quality. Predicting saltwater upconing is critical for maintaining a long-term supply of water of good quality to the Groundwater Management District No. 5. This paper uses a numerical model to predict the effect of saltwater upconing on the salinity of pumped water. A sensitivity analysis was conducted for estimating the effects of uncertainties in model parameters on the numerical results. The most important factors affecting the salinity of discharged water are found to be the location and nature of clay layers in the aquifer, the pumping rate, the location of the well screen, and the hydraulic conductivities of the medium. The effect of uncertainties in aquifer porosity and dispersivity on salinity is appreciable but not substantial, whereas that of recharge from precipitation in the study area is relatively insignificant. In addition, a numerical model based on the field conditions observed at the Siefkes site was constructed and calibrated to reproduce and project the variation of measured water levels and discharged groundwater concentration. Finally, a number of practical management recommendations based on this study are presented.

Journal of Hydrology↗

USGS2012

Geochemistry of thermal waters in Long Valley, Mono County, California

Thermal springs and wells in Long Valley, California, issue sodium bicarbonate‐chloride waters containing 1000–1420 mg/l of dissolved solids. Thermal waters of sodium bicarbonate‐chloride composition are usually associated with hot‐water reservoirs. Chloride concentrations and stable isotope data indicate that the thermal waters have had varied histories. All of the thermal springs issue a mixture of fluid from the thermal reservoir and less saline, cooler water from one or more shallow aquifers. The composition of springs in Hot Creek Gorge may have been further altered by minor subsurface boiling. Thermal springs between Hot Creek and Lake Crowley issue mixtures of fresh and thermal waters which have lost heat by conductive cooling and changed composition by reaction with rock in the shallow aquifer. The silica content of water from Magma Richie 5 and mixing calculations based on the concentrations of silica in thermal waters collected from springs in Hot Creek Gorge and along Little Hot Creek indicate a temperature of at least 200°C in the thermal reservoir. The sodium‐potassium‐calcium geothermometer yields a reservoir temperature estimate near 200°C for most of the thermal springs. If geothermal energy is developed in Long Valley, the high concentrations of arsenic (up to 2.2 mg/l), boron (up to 15 mg/l), and total dissolved solids in the thermal fluids will make it necessary to isolate the effluent of production wells from the freshwater system.

California↗

USGS1985

Hydraulic gradient control for groundwater contaminant removal

The Rocky Mountain Arsenal near Denver, Colorado, U.S.A., is used as a realistic setting for a hypothetical test of a procedure that plans the hydraulic stabilization and removal of a groundwater contaminant plume. A two-stage planning procedure successfully selects the best wells and their optimal pumping/recharge schedules to contain the plume while a well or system of wells within the plume removes the contaminated water. In stage I, a combined groundwater flow and solute transport model is used to simulate contaminant removal under an assumed velocity field. The result is the approximated plume boundary location as a function of time. In stage II, a linear program, which includes a groundwater flow model as part of the set of constraints, determines the optimal well selection and their optimal pumping/recharge schedules by minimizing total pumping and recharge. The simulation—management model eliminates wells far from the plume perimeter and activates wells near the perimeter as the plume decreases in size. This successfully stablizes the hydraulic gradient during aquifer cleanup.

Colorado↗

USGS2020

Lava–water interaction and hydrothermal activity within the 2014–2015 Holuhraun Lava Flow Field, Iceland

Lava that erupted during the 2014–2015 Holuhraun eruption in Iceland flowed into a proglacial river system, resulting in aqueous cooling of the lava and an ephemeral hydrothermal system. We carried out a monitoring study of this system from 2015 to 2018 to document the cooling of the lava over this time, using thermocouple measurements and data-logging sensors. The heat loss rate from advection through this hydrothermal system in August 2015 was ~5.5 × 10 8 W; since eruption, aqueous cooling likely accounted for ~1% of the total heat loss from the lava. This estimate excludes steam losses from fumaroles as well as any groundwater that was not released to the surface, and thus is a lower bound. Near the terminus of the flow, advection of heat by flowing water may have locally accounted for tens of percent of the total cooling of that part of the flow. Our data quantify the importance of water cooling for this lava flow and can be compared with models to better understand lava–water interactions more generally. We also provide detailed methods for simple, low-cost monitoring of similar instances in the future.

Holuhraun Lava Flow Field↗

USGS2008

Mapping the information landscape: Discerning peaks and valleys for ecological monitoring

We investigate previously unreported phenomena that have a potentially significant impact on the design of surveillance monitoring programs for ecological systems. Ecological monitoring practitioners have long recognized that different species are differentially informative of a system's dynamics, as codified in the well-known concepts of indicator or keystone species. Using a novel combination of analysis techniques from nonlinear dynamics, we describe marked variation among spatial sites in information content with respect to system dynamics in the entire region. We first observed these phenomena in a spatially extended predator-prey model, but we observed strikingly similar features in verified water-level data from a NOAA/NOS Great Lakes monitoring program. We suggest that these features may be widespread and the design of surveillance monitoring programs should reflect knowledge of their existence.

Journal of Biological Physics↗

USGS1998

Developmental geology of coalbed methane from shallow to deep in Rocky Mountain basins and in Cook Inlet-Matanuska Basin, Alaska, USA and Canada

The Rocky Mountain basins of western North America contain vast deposits of coal of Cretaceous through early Tertiary age. Coalbed methane is produced in Rocky Mountain basins at depths ranging from 45 m (150 ft) to 1981 m (6500 ft) from coal of lignite to low-volatile bituminous rank. Although some production has been established in almost all Rocky Mountain basins, commercial production occurs in only a few. despite more than two decades of exploration for coalbed methane in the Rocky Mountain region, it is still difficult to predict production characteristics of coalbed methane wells prior to drilling. Commonly cited problems include low permeabilities, high water production, and coals that are significantly undersaturated with respect to methane. Sources of coalbed gases can be early biogenic, formed during the early stages of coalification, thermogenic, formed during the main stages of coalification, or late stage biogenic, formed as a result of the reintroduction of methane-gnerating bacteria by groundwater after uplift and erosion. Examples of all three types of coalbed gases, and combinations of more than one type, can be found in the Rocky Mountain region. Coals in the Rocky Mountain region achieved their present ranks largely as a result of burial beneath sediments that accumulated during the Laramide orogeny (Late Cretaceous through the end of the eocene) or shortly after. Thermal events since the end of the orogeny have also locally elevated coal ranks. Coal beds in the upper part of high-volatile A bituminous rank or greater commonly occur within much more extensive basin-centered gas deposits which cover large areas of the deeper parts of most Rocky Mountain basins. Within these basin-centered deposits all lithologies, including coals, sandstones, and shales, are gas saturated, and very little water is produced. The interbedded coals and carbonaceous shales are probably the source of much of this gas. Basin-centered gas deposits become overpressured from hydrocarbon generation as they form, and this overpressuring is probably responsible for driving out most of the water. Sandstone permeabilities are low, in part because of diagenesis caused by highly reactive water given off during the early stages of coalification. Coals within these basin-centered deposits commonly have high gas contents and produce little water, but they generally occur at depths greater than 5000 ft and have low permeabilities. Significant uplift and removal of overburden has occurred throughout the Rocky Mountain region since the end of the Eocene, and much of this erosion occurred after regional uplift began about 10 Ma. The removal of overburden generally causes methane saturation levels in coals to decrease, and thus a significant drop in pressure is required to initiate methane production. The most successful coalbed methane production in the Rocky Mountain region occurs in areas where gas contents were increased by post-Eocene thermal events and/or the generation of late-stage biogenic gas. Methane-generating bacteria were apparently reintroduced into the coals in some areas after uplift and erosion, and subsequent changes in pressure and temperature, allowed surface waters to rewater the coals. Groundwater may also help open up cleat systems making coals more permeable to methane. If water production is excessive, however, the economics of producing methane are impacted by the cost of water disposal.The Rocky Mountain basins of western North America contain vast deposits of coal of Cretaceous through early Tertiary age. Coalbed methane is produced in Rocky Mountain basins at depths ranging from 45 to 1981 m from coal of lignite to low volatile bituminous rank. Despite more than two decades of exploration for coalbed methane in Rocky Mountain region, it is still difficult to predict production characteristics of coalbed methane wells prior to drilling. Sources of coalbed gases can be early biogenic, formed during the main stages of coa

International Journal of Coal Geology↗