Browsing by Author "Ripepi, Nino"

Now showing 1 - 9 of 9
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    Application of Double-Difference Seismic Tomography to Carbon Sequestration Monitoring at the Aneth Oil Field, Utah
    Slaker, Brent; Westman, Erik C.; Luxbacher, Kramer Davis; Ripepi, Nino (MDPI, 2013-10-23)
    Double difference seismic tomography was performed using travel time data from a carbon sequestration site at the Aneth oil field in southeast Utah as part of a Department of Energy initiative on monitoring, verification, and accounting (MVA) of sequestered CO2. A total of 1211 seismic events were recorded from a borehole array consisting of 23 geophones. Artificial velocity models were created to determine the likelihood of detecting a CO2 plume with an unfavorable event and receiver arrangement. In tests involving artificially modeled ray paths through a velocity model, ideal event and receiver arrangements clearly show velocity reductions. When incorporating the unfavorable event and station locations from the Aneth Unit into synthetic models, the ability to detect velocity reductions is greatly diminished. Using the actual, recorded travel times, the Aneth Unit results show differences between a synthetic baseline model and the travel times obtained in the field, but the differences do not clearly indicate a region of injected CO2. MVA accuracy and precision may be improved through the use of a receiver array that provides more comprehensive ray path coverage, and a more detailed baseline velocity model.
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    Coal Mining Outlook: International, National, and Virginia Trends
    Karmis, Michael E.; McDowney, Preston; Ripepi, Nino; Schafrik, Steven J.; Weisiger, Sean; Walton, Daniel; Kostic, Dennis (Virginia Tech. Virginia Center for Coal and Energy Research., 2000-11)
    Coal mining serves an important role as the economic catalyst for Southwest Virginia, providing high paying jobs in an area crippled by unemployment. There are numerous support industries in existence only because of coal mining. The ripple effects of mining are experienced throughout the state. Every ton of coal mined in Virginia contributes $27.11 to Virginia's economy, while every dollar paid to a miner has a $4.64 impact on Virginia's economy. The tax credit has had a pronounced effect on coal production in Virginia. After the tax credit was enacted, the declining trend in coal production has slowed down, and the production levels are higher than projected. As a result of these higher production levels, an additional $394 million in total impact has been generated, millions in severance and income taxes have been produced, and numerous coal mining jobs have been preserved.
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    A Data-Driven Approach for the Development of a Decision Making Framework for Geological CO2 Sequestration in Unmineable Coal Seams
    Miskovic, Ilija (Virginia Tech, 2011-12-14)
    In today's energy constrained world, carbon capture and sequestration can play an essential role in mitigating greenhouse gas emissions, while simultaneously maintaining a robust and affordable energy supply. This technology is an end-of-pipe solution that does not contribute to a decrease of the production of greenhouse gases, but is very useful as a transition solution on the way towards other sustainable energy production mechanisms. This research involves the development of a comprehensive decision making framework for assessing the techno-economic feasibility of CO2 sequestration in unmineable coal seams, with the Central Appalachian Basin chosen for analysis due to the availability of empirical data generated through recent characterization and field validation studies. The studies were conducted in order to assess the sequestration capacity of coal seams in the Central Appalachian Basin and their potential for enhanced coal bed methane recovery. The first stage of this research involves assessment of three major sequestration performance parameters: capacity, injectivity, and containment. The assessment is focused on different attributes and reservoir properties, characteristic of deep unmineable coal seams in the Central Appalachian Basin. Quantitative and qualitative conclusions obtained through this review process are used later in the identification of the minimum set of technical information necessary for effective design and development of CO2 storage operations. The second section of this dissertation analyzes economic aspects of CO2 sequestration. This segment of the research uses a real options analysis to evaluate the impact of major sources of uncertainty on the total cost of developing and operating a CCS project in a regulatory environment that expects implementation of carbon taxes, but with uncertainty about the timing of this penalty. Finally, all quantitative and qualitative information generated in the first two stages of this research were used for development of a decision making framework/matrix that summarizes the interactions between major technical and economic parameters and constraints, on the other hand, and their impact on overall feasibility of CO2 sequestration in unmineable coal seams. This framework will provide user with capability to address complex problems in a more systematic way and to analyze the most efficient way to utilize available resources.
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    Determining Coalbed Methane Production and Composition from Individual Stacked Coal Seams in a Multi-Zone Completed Gas Well
    Ripepi, Nino; Louk, Kyle; Amante, Joseph; Schlosser, Charlies; Tang, Xu; Gilliland, Ellen (MDPI, 2017-10-02)
    This work proposes a novel and cost-effective approach to determine coalbed methane (CBM) production and composition from individual coal seams in a multi-zone completed CBM well. The novel method uses water to cover individual coal seams in a low pressure CBM well followed by an Echometer fluid level survey to determine the water level. Corresponding gas flow measurements and natural gas chromatography analysis are used to determine gas production and composition from unique zones. A field test using this technology is conducted in Central Appalachia for a multi-zone CBM well containing 18 coal seams. Test results show that the shallow coal seams contribute the majority of the total CBM production in this multi-zone well, and the deeper coal seams contain more heavy hydrocarbons like ethane and propane.
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    Double-Difference Tomography Applied to Monitoring of Geologic Carbon Sequestration in the Aneth Oil Field, Utah
    Slaker, Brent (Virginia Tech, 2011-12-06)
    Double-difference seismic tomography is performed on a carbon sequestration operation in the Aneth Oil Field in southeast Utah as part of a Department of Energy initiative on monitoring, verification, and accounting of sequestered CO2. A total of 1,211 seismic events were recorded from a borehole array of 22 geophones. Aneth Unit data were divided into four time periods for time-lapse analysis. A low velocity zone spanning the lateral extents of the observable region, likely representing a CO2 plume, is detected when considering voxels containing the highest ray path coverage. A series of synthetic tomography tests simulating different CO2 plume sizes and locations was performed to assist in characterizing velocity changes associated with Aneth Unit data. Inferences about the existence of a CO2 plume should be made by comparing actual data to synthetic data resulting from simulations performed under similar conditions. Considering synthetic simulation similarities and a derivative weight sum analysis, a CO2 plume can be imaged within the Desert Creek reservoir, but the resolution of the CO2 plume is too low for proper monitoring, verification, and accounting of injected CO2. Recommendations, for improving CO2 plume resolution through double difference seismic tomography, are made to increase the ray path distribution throughout the Aneth Unit by varying geophone locations.
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    Field Laboratory for Emerging Stacked Unconventional Plays (ESUP): Project No. DE-FE0031576
    Ripepi, Nino; Karmis, Michael E.; Chen, Cheng; Gilliland, Ellen; Nojabaei, Bahareh (Virginia Tech, 2018-08-24)
    The objective for this project is to investigate and characterize the resource potential for multi-play production of emerging unconventional reservoirs in Central Appalachia. The project team includes Virginia Tech; Virginia Center for Coal & Energy Research; Enervest Operating, LCC; Pashin Geoscience, LLC; and Gerald R. Hill, PhD, Inc. The anticipated duration of the project is April 1, 2018 - March 31, 2023.
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    Kerogen nanoscale structure and CO2 adsorption in shale micropores
    Gonciaruk, Aleksandra; Hall, Matthew R.; Fay, Michael W.; Parmenter, Christopher D. J.; Vane, Christopher H.; Khlobystov, Andrei N.; Ripepi, Nino (2021-02-16)
    Gas storage and recovery processes in shales critically depend on nano-scale porosity and chemical composition, but information about the nanoscale pore geometry and connectivity of kerogen, insoluble organic shale matter, is largely unavailable. Using adsorption microcalorimetry, we show that once strong adsorption sites within nanoscale network are taken, gas adsorption even at very low pressure is governed by pore width rather than chemical composition. A combination of focused ion beam with scanning electron microscopy and transmission electron microscopy reveal the nanoscale structure of kerogen includes not only the ubiquitous amorphous phase but also highly graphitized sheets, fiber- and onion-like structures creating nanoscale voids accessible for gas sorption. Nanoscale structures bridge the current gap between molecular size and macropore scale in existing models for kerogen, thus allowing accurate prediction of gas sorption, storage and diffusion properties in shales.
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    Micrometer-scale Experimental Characterization of the Lower Huron Shale in the Central Appalachian Basin
    Tan, Xinyu; Gilliland, Ellen; Tang, Xu; Fan, Ming; Ripepi, Nino (American Geophysical Union, 2020)
    The mechanical properties of shale play an important role in hydraulic fracturing design. Although the popular nanoindentation method can be performed to evaluate some mechanical characteristics of organic matter, it is still difficult to fully characterize mechanical properties of organic components of shale due to their small scale which is usually on the order of micrometers or even nanometers. As a novel material characterization tool, Atomic Force Microscopy (AFM) has shown great potential to characterize surface properties and pore structures at micrometer- and nanometer-scale and has been applied to investigate the elastic properties of organic components in shale by multiple researchers. Raman and FTIR can detect chemical bands by utilizing molecular vibration information. Because Raman and FTIR measurements are non-destructive, high sensitivity, and short in duration, they have been used extensively to study maturation processes of organic components in coal and shale samples. To some extent, these two methods can be considered as complementary to each other, and more comprehensive understanding about maturation processes of organic components can be achieved by combining these two methods. In this work, mechanical properties and chemical characteristics of four shale samples with different thermal maturities were investigated. Generally, this study had two objectives: (1) Characterize the mechanical properties of shale samples with different maturity levels through the novel AFM method, and (2) Explore the underlying cause for the change in elastic properties of shale samples from a chemical perspective through the complementary Raman and FTIR methods.
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    Stochastic Continuous Modeling for Pillar Stress Estimation and Comparison with 2D Numerical, and Analytical Solutions in an Underground Stone Mine
    Monsalve, Juan J.; Soni, Aman; Karfakis, Mario; Hazzard, Jim; Ripepi, Nino (Springer, 2022-09)
    Pillar collapses are events that due to their severe consequences can be classified as high risk. The design of pillars in underground room-and-pillar operations should migrate to risk-based design approaches. The authors of this work proposed a risk-based pillar design methodology that integrates stochastic discrete element modeling for pillar strength estimation, and stochastic finite volume modeling (FVM) for stress estimation. This paper focuses on the stochastic FVM component for stress estimation. The mining and geomechanical aspects of a case study mine (CSM) are described and pillar stresses are estimated by using three approaches: (1) analytical solutions, (2) 2D finite element modeling, and (3) 3D finite volume modeling. This operation extracts a 30 degrees dipping deposit, which makes current underground stone mine design guidelines inapplicable for this CSM. This work compares results from each stress estimation approach and discusses uses the point estimate method as a simplified stochastic approach to evaluate the effect of rock mass elastic properties variability on pillar stress distribution. Results from this work show that the three estimation approaches lead to different estimations, possibly, due to the wide range of assumptions each estimation approach considers. It was also determined that the horizontal to vertical stress ratio has a significant impact on pillar stress magnitude. Therefore, it is recommended to perform in situ stress measurements, or assume worst-case-scenario values to account and reduce uncertainty due to this parameter. The stochastic stress estimation approach used in this paper provides results that can integrate a risk-based pillar design framework.