CO2 storage and enhanced coalbed methane recovery: Reservoir characterization and fluid flow simulations of the Big George coal,Powder River Basin,Wyoming, USA

Coalbeds are an attractive geological environment for storage of carbon dioxide (CO₂) because CO₂ is retained in the coal as an adsorbed phase and the cost of injection can be offset by enhanced coalbed methane (ECBM) production. This paper presents the findings of a CO₂ storage feasibility study on coalbeds in the Wyodak-Anderson coal zone of the Powder River Basin, Wyoming, USA, using reservoir characterization and fluid flow simulations. A 3D numerical model of the Big George coal was constructed using geostatistical techniques, with values of cleat and matrix permeability and porosity constrained through history-matching of production data from coalbed methane (CBM) wells in the field area.Following history-matching, several ECBM and CO₂ storage scenarios were investigated: shrinkage and swelling of the coal was either allowed or disallowed, a horizontal hydraulic fracture was either placed at the injection well or removed from the model, the number of model layers was varied between 1 and 24, and the permeability and porosity fields were constructed to be either homogeneous or heterogeneous in accordance with geostatistical models of regional variability. All simulations assumed that the injected gas was 100% CO₂ and that the coalbed was overlain by an impermeable caprock. Depending on the scenario, the simulations predicted that after 13 years of CO₂ injection, the cumulative methane production would be enhanced by a factor of 1.5–5. Including coal matrix shrinkage and swelling in the model predicted swelling near the injection well, which resulted in a slight reduction (10%) in injection rate. However, including a horizontal hydraulic fracture in the model at the base of the injection well helped mitigate the negative effect of swelling on injection rate. It was also found that six model layers were needed to have sufficient resolution in the vertical direction to account for the buoyancy effects between the gas and resident water, and that capturing the heterogeneous nature of the coal permeability and porosity fields predicted lower estimates of the storage capacity of the Wyodak-Anderson coal zone.After noting that gravity and buoyancy were the major driving forces behind gas flow within the Big George coal, several leakage scenarios were also investigated, in an effort to better understand the interplay between diffusion and flow properties on the transport and storage of CO₂. The modeling predicted that the upward migration of gas due to the buoyancy effect was faster than the diffusion of CO₂ and therefore the gas rapidly rose to the top of the coalbed and migrated into overlying strata when an impermeable caprock was not included in the model.     

Impact of chlorine exposure time on disinfection byproduct formation in the presence of iopamidol and natural organic matter during chloramination

Chloramines,in practice,are formed onsite by adding ammonia to chlorinated drinking water to achieve the required disinfection.While regulated disinfection byproducts(DBPs)are reduced during chloramine disinfection,other DBPs such as iodinated(iodo-)DBPs,that elicit greater toxicity are formed.The objective of this study was to investigate the impact of prechlorination time on the formation of both halogen-specific total organic halogen(TOX)and iodo/chlorinated(chloro-)DBPs during prechlorination/chloramination in source waters(SWs)containing iopamidol,an X-ray contrast medium.Barberton SW(BSW)and Cleveland SW(CSW)containing iopamidol were prechlorinated for 5–60 min and afterwards chloraminated for 72 hr with ammonium chloride.Chlorine contact time(CCT)did not significantly impact total organic iodine(TOI)concentrations after prechlorination or chloramination.Concentrations of total organic chlorine(TOCl)formed during prechlorination did not significantly change regardless of pH and prechlorination time,whileTOClappearedtodecreaseafter 72 hrchloraminationperiod.Dichloroiodomethane(CHCl_2I)formation during prechlorination did not exhibit any significant trends as a function of p H or CCT,but after chloramination,significant increases were observed at pHs 6.5 and 7.5 with respect to CCT.Iodo-HAAs were not formed during prechlorination but were detected after chloramination.Significant quantities of chloroform(CHCl_3)and trichloroacetic acid(TCAA)were formed during prechlorination but formation ceased upon ammonia addition.Therefore,prechlorination studies should measure TOX and DBP concentrations prior to ammonia addition to obtain data regarding the initial conditions.     

A global empirical typology of anthropogenic drivers of environmental change in deltas

It is broadly recognized that river delta systems around the world are under threat from a range of anthropogenic activities. These activities occur at the local delta scale, at the regional river and watershed scale, and at the global scale. Tools are needed to support generalization of results from case studies in specific deltas. Here, we present a methodology for quantitatively constructing an empirical typology of anthropogenic change in global deltas. Utilizing a database of environmental change indicators, each associated with increased relative sea-level rise and coastal wetland loss, a clustering analysis of 48 global deltas provides a quantitative assessment of systems experiencing similar or dissimilar sources and degrees of anthropogenic stress. By identifying quantitatively similar systems, we hope to improve the transferability of scientific results across systems, and increase the effectiveness of delta management best practices. Both K-Means and Affinity Propagation clustering algorithms find similar clusters, with relative stability across small changes in K-Means cluster number. High-latitude deltas appear similar, in terms of anthropogenic environmental stress, to several low-population, low-latitude systems, including the Amazon delta, despite substantially different climatic regimes. Highly urbanized deltas in Southeast Asia form a distinct cluster. By providing a quantitative boundary between groups of delta systems, this approach may also be useful for assessing future delta change and sustainability given projected population growth, urbanization, and economic development trends.     

Restoring islands and identifying source populations for introductions

Article impact statement: Structured decision making can be used to identify an optimal source population for conservation introductions.     

Real-world vehicle emissions: a summary of the Seventeenth Coordinating Research Council On-Road Vehicle Emissions Workshop

The Coordinating Research Council, Inc. (CRC) held its 17th On-Road Vehicle Emissions Workshop in March 2007, where results of the most recent on-road vehicle emissions research were presented. We summarize ongoing work from researchers who are engaged in improving our understanding of the role and contribution of mobile sources to ambient air quality and emission inventories. Participants in the Workshop discussed efforts to improve mobile source emission models, light- and heavy-duty vehicle emissions measurements, on- and off-road emissions measurements, effects of fuels and lubricating oils on emissions, as well as emerging issues and topics for future research.     

Innovation in the Knowledge Age: implications for collaborative science

Current trends validate the notion that multifaceted, multimodal interdisciplinary collaborations lead to increased research productivity in publications and citations, compared to those achieved by individual researchers. Moreover, it may be that scientific breakthroughs are increasingly achieved by interdisciplinary research teams. Nonetheless, despite the perceived importance of collaboration and its bibliometric benefits, today’s scientists are still trained to be autonomous, work individually, and encourage their graduate students to do the same—perpetuating values which impede the creation of collaborative space between disciplines. As a consequence, scientists working in teams typically report serious obstacles to collaboration. This paper builds off of recent recommendations from a 2015 National Academies report on the state of team science which emphasizes greater definition of roles, responsibility, accountability, goals, and milestones. However, these recommendations do not address the subjective, relational components of collaboration which can drive innovation and creativity. The relational side of collaboration is key to understanding the capacity and capabilities of the knowledge workers, such as scientists and engineers, who comprise interdisciplinary research teams. The authors’ recommendations, grounded in organizational communication and knowledge worker literature, include a renewed focus on the process of organizing through communication rather than focusing on organization as an outcome or consequence of teamwork, leading and cultivating team members rather than managing them, and the need to address self-driven, rather than external, motivations to engage in knowledge work.     

Global change impacts on the Upper Danube Catchment (Central Europe): a study of participatory modeling

Participatory modeling (PM) has become an essential concept in environmental impact assessment and planning in the field of water resources. In this paper, we focus on the use of PM to support the development of the integrated regional modeling system DANUBIA as a scientific concept to analyze the previously unknown impacts of global change, i.e., the combined effects of climate, demographic, economic, social and ecological change, on the Upper Danube Catchment (Germany). We use this case study to examine the specific conditions for PM in the field of complex integrated models on a regional scale. We describe the stepwise PM process and discuss the respective results, focusing on (1) the stakeholder dialogue’s contribution in supporting the development of new, complex modeling systems, particularly on a regional scale, (2) conditions of stakeholder involvement in issues related to the distant future, such as climate change impacts on regional water availability, and (3) limitations of PM and scientists’ motivation to carry out participatory research at all. We conclude that the PM process was not entirely successful in improving the scientific quality and practical applicability of the developed models because the process goals were manifold and overambitious, and the definition of the problem of “global change impacts on a regional scale” was too weak and uncertain to allow for a clear common objective of modelers and stakeholders. We claim that there is a lack of incentives for scientists, particularly natural scientists, to commit to PM activities.     

An Integrated Approach to Street Canyon Pollution Modelling

An integrated method for the prediction of the spatial pollution distribution within a street canyon directly from a microscopic traffic simulation model is outlined. The traffic simulation package Paramics is used to model the flow of vehicles in realistic traffic conditions on a real road network. This produces details of the amount of pollutant produced by each vehicle at any given time. The authors calculate the dispersion of the pollutant using a particle tracking diffusion method which is superimposed on a known velocity and turbulence field. This paper shows how these individual components may be integrated to provide a practical street canyon pollution model. The resulting street canyon pollution model provides isoconcentrations of pollutant within the road topography.