The Experts below are selected from a list of 2895 Experts worldwide ranked by ideXlab platform
Michael A. Celia - One of the best experts on this subject based on the ideXlab platform.
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measuring methane emissions from Abandoned and active oil and gas Wells in west virginia
Science of The Total Environment, 2019Co-Authors: Stuart N Riddick, Mary Kang, Denise L Mauzerall, Michael A. Celia, Kara Bressler, Christopher Chu, Caleb D GumAbstract:Abstract Recent studies have reported methane (CH4) emissions from Abandoned and active oil and gas infrastructure across the United States, where measured emissions show regional variability. To investigate similar phenomena in West Virginia, we measure and characterize emissions from Abandoned and active conventional oil and gas Wells. In addition, we reconcile divergent regional CH4 emissions estimates by comparing our West Virginia emissions estimates with those from other states in the United States. We find the CH4 emission factors from 112 plugged and 147 unplugged Wells in West Virginia are 0.1 g CH4 h−1 and 3.2 g CH4 h−1, respectively. The highest emitting unplugged Abandoned Wells in WV are those most recently Abandoned, with the mean emission of Wells Abandoned between 1993 and 2015 of 16 g CH4 h−1 compared to the mean of those Abandoned before 1993 of 3 × 10−3 g CH4 h−1. Using field observations at a historic mining area as a proxy for state-wide drilling activity in the late 19th/early 20th century, we estimate the number of Abandoned Wells in WV at between 60,000 and 760,000 Wells. Methane emission factors from active conventional Wells were estimated at 138 g CH4 h−1. We did not find an emission pattern relating to age of Wells or operator for active Wells, however, the CH4 emission factor for active conventional Wells was 7.5 times larger than the emission factor used by the EPA for conventional oil and gas Wells. Our results suggest that well emission factors for active and Abandoned Wells can vary within the same geologic formation and may be affected by differences in state regulations. Therefore, accounting for state-level variations is critical for accuracy in greenhouse gas emissions inventories, which are used to guide emissions reduction strategies.
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Estimates of CO2 leakage along Abandoned Wells constrained by new data
International Journal of Greenhouse Gas Control, 2019Co-Authors: Tom J.w. Postma, Karl W. Bandilla, Michael A. CeliaAbstract:Abstract The viability of carbon capture and geological storage (CCS) projects depends in part on the risk that injected CO2 or displaced pore fluid will leak out of the target formation into surrounding formations or to the surface. Abandoned oil and gas Wells, of which millions exist both throughout the United States and globally, form a potential conduit for this leakage. Recently, specific field measurements have been made to quantify the range of effective permeabilities that can be expected in Abandoned Wells, enabling us to, for the first time, combine field-scale numerical simulations of CO2 sequestration in deep saline aquifers with real data on effective permeabilities of leaky Wells. Using a previously developed semi-analytical reservoir simulator that can accommodate an arbitrary sequence of alternating aquifers and aquicludes, as well as an arbitrary number of leaky Wells, we investigated how the amount of CO2 that leaks out of the target formation depends on the spatial density of nearby Abandoned Wells and their effective permeability. Furthermore, we assess the influence that variations in pressure and temperature found between geological targets have on this dependency. We find that the observed differences in leakage between geological targets are controlled almost exclusively by differences in density of CO2 at the local subsurface conditions, causing the CO2 plume to contact a different number of Wells when injecting at the same constant mass rate. We quantitatively assess the results obtained from our numerical experiments by combining them with the permeability data that have recently become available, typical spatial densities of Abandoned Wells, and performance requirements put forward in the literature. Our results indicate that leakage of CO2 through Abandoned Wells is unlikely to be a major limitation in storage security of CCS projects.
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Identification and characterization of high methane-emitting Abandoned oil and gas Wells
Proceedings of the National Academy of Sciences, 2016Co-Authors: Mary Kang, Shanna Christian, Alana R. Miller, Markus Bill, Mark E Conrad, Thomas H Darrah, Yuheng Chen, Denise L Mauzerall, Michael A. Celia, Robert B. JacksonAbstract:Recent measurements of methane emissions from Abandoned oil/gas Wells show that these Wells can be a substantial source of methane to the atmosphere, particularly from a small proportion of high-emitting Wells. However, identifying high emitters remains a challenge. We couple 163 well measurements of methane flow rates; ethane, propane, and n-butane concentrations; isotopes of methane; and noble gas concentrations from 88 Wells in Pennsylvania with synthesized data from historical documents, field investigations, and state databases. Using our databases, we (i) improve estimates of the number of Abandoned Wells in Pennsylvania; (ii) characterize key attributes that accompany high emitters, including depth, type, plugging status, and coal area designation; and (iii) estimate attribute-specific and overall methane emissions from Abandoned Wells. High emitters are best predicted as unplugged gas Wells and plugged/vented gas Wells in coal areas and appear to be unrelated to the presence of underground natural gas storage areas or unconventional oil/gas production. Repeat measurements over 2 years show that flow rates of high emitters are sustained through time. Our attribute-based methane emission data and our comprehensive estimate of 470,000–750,000 Abandoned Wells in Pennsylvania result in estimated state-wide emissions of 0.04–0.07 Mt (1012 g) CH4 per year. This estimate represents 5–8% of annual anthropogenic methane emissions in Pennsylvania. Our methodology combining new field measurements with data mining of previously unavailable well attributes and numbers of Wells can be used to improve methane emission estimates and prioritize cost-effective mitigation strategies for Pennsylvania and beyond.
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Direct measurements of methane emissions from Abandoned oil and gas Wells in Pennsylvania
Proceedings of the National Academy of Sciences, 2014Co-Authors: Mary Kang, Cynthia M. Kanno, Matthew C. Reid, Yuheng Chen, Denise L Mauzerall, Michael A. Celia, Xin Zhang, Tullis C OnstottAbstract:Abandoned oil and gas Wells provide a potential pathway for subsurface migration and emissions of methane and other fluids to the atmosphere. Little is known about methane fluxes from the millions of Abandoned Wells that exist in the United States. Here, we report direct measurements of methane fluxes from Abandoned oil and gas Wells in Pennsylvania, using static flux chambers. A total of 42 and 52 direct measurements were made at Wells and at locations near the Wells ("controls") in forested, wetland, grassland, and river areas in July, August, October 2013 and January 2014, respectively. The mean methane flow rates at these well locations were 0.27 kg/d/well, and the mean methane flow rate at the control locations was 4.5 × 10(-6) kg/d/location. Three out of the 19 measured Wells were high emitters that had methane flow rates that were three orders of magnitude larger than the median flow rate of 1.3 × 10(-3) kg/d/well. Assuming the mean flow rate found here is representative of all Abandoned Wells in Pennsylvania, we scaled the methane emissions to be 4-7% of estimated total anthropogenic methane emissions in Pennsylvania. The presence of ethane, propane, and n-butane, along with the methane isotopic composition, indicate that the emitted methane is predominantly of thermogenic origin. These measurements show that methane emissions from Abandoned oil and gas Wells can be significant. The research required to quantify these emissions nationally should be undertaken so they can be accurately described and included in greenhouse gas emissions inventories.
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Detecting leakage of brine or CO2 through Abandoned Wells in a geological sequestration operation using pressure monitoring Wells
Energy Procedia, 2011Co-Authors: Juan P. Nogues, Jan Nordbotten, Michael A. CeliaAbstract:Abstract For risk assessment, policy design and GHG emission accounting it is extremely important to know if any CO 2 or brine has leaked from a geological sequestration (GS) operation. As such, it is important to understand if it is possible to use certain technologies to detect it. This detection of leakage is one of the most challenging problems associated with GS due to the high uncertainty in the nature and location of leakage pathways. In North America for example millions of legacy oil and gas Wells present the possibility of CO 2 and brine to leak out of the injection formation. The available information for these potential leaky Wells is very limited and the main parameters that control leakage, like permeability of the sealing material are not known. Here we propose to explore the possibility of detecting such leakage by the use of pressure-monitoring Wells located in a formation overlying the injection formation. The detection analysis is based on a system of equations that solve for the propagation of a pressure pulse using the superposition principle and an approximation to the well function. We explore the questions of what can be gained by using pressure-monitoring Wells and what are the limitations given a specific accuracy threshold of the measuring device. We also try to answer the question of where these monitoring Wells should be placed to optimize the objective of a monitoring scheme. We believe these results can ultimately lead to practical design strategies for monitoring schemes, including quantitative estimation of increased probability of leak detection per added observation well.
Mohan D. Gupte - One of the best experts on this subject based on the ideXlab platform.
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A malaria outbreak in Naxalbari, Darjeeling district, West Bengal, India, 2005: weaknesses in disease control, important risk factors.
Malaria Journal, 2009Co-Authors: Puran K. Sharma, Ramakrishnan Ramanchandran, Raju Sharma, Yvan Hutin, Mohan D. GupteAbstract:An outbreak of malaria in Naxalbari, West Bengal, India, in 2005 was investigated to understand determinants and propose control measures. Malaria cases were slide-confirmed. Methods included calculation of annual blood examination rates (ABER, number of slides examined/population), collection of water specimens from potential vector-breeding sites, sorting of villages in categories depending on the number of Abandoned Wells within two kilometers radius and review of the DDT spray coverage. Cases were compared with matched neighbourhood controls in terms of personal protection using matched odds ratios (MOR). 7,303 cases and 17 deaths were reported between April 2005 and March 2006 with a peak during October rains (Attack rate: 50 per 1,000, case fatality: 0.2%). The attack rate increased according to the number of Abandoned Wells within 2 kilometres radius (P < 0.0001, Chi-square for trend). Abandoned Wells were Anopheles breeding sites. Compared with controls, cases were more likely to sleep outdoors (MOR: 3.8) and less likely to use of mosquito nets and repellents (MOR: 0.3 and 0.1, respectively). DDT spray coverage and ABER were 39% and 3.5%, below the recommended 85% and 10%, respectively. Overall, this outbreak resulted from weaknesses in malaria control measures and a combination of factors, including vector breeding, low implementation of personal protection and weak case detection.
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A malaria outbreak in Naxalbari, Darjeeling district, West Bengal, India, 2005: weaknesses in disease control, important risk factors.
Malaria Journal, 2009Co-Authors: Puran K. Sharma, Ramakrishnan Ramanchandran, Raju Sharma, Yvan Hutin, Mohan D. GupteAbstract:An outbreak of malaria in Naxalbari, West Bengal, India, in 2005 was investigated to understand determinants and propose control measures. Malaria cases were slide-confirmed. Methods included calculation of annual blood examination rates (ABER, number of slides examined/population), collection of water specimens from potential vector-breeding sites, sorting of villages in categories depending on the number of Abandoned Wells within two kilometers radius and review of the DDT spray coverage. Cases were compared with matched neighbourhood controls in terms of personal protection using matched odds ratios (MOR). 7,303 cases and 17 deaths were reported between April 2005 and March 2006 with a peak during October rains (Attack rate: 50 per 1,000, case fatality: 0.2%). The attack rate increased according to the number of Abandoned Wells within 2 kilometres radius (P < 0.0001, Chi-square for trend). Abandoned Wells were Anopheles breeding sites. Compared with controls, cases were more likely to sleep outdoors (MOR: 3.8) and less likely to use of mosquito nets and repellents (MOR: 0.3 and 0.1, respectively). DDT spray coverage and ABER were 39% and 3.5%, below the recommended 85% and 10%, respectively. Overall, this outbreak resulted from weaknesses in malaria control measures and a combination of factors, including vector breeding, low implementation of personal protection and weak case detection.
Natalie J. Pekney - One of the best experts on this subject based on the ideXlab platform.
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Historic and Modern Approaches for the Discovery of Abandoned Wells for Methane Emissions Mitigation in Oil Creek State Park, Pennsylvania
Environmental Management, 2021Co-Authors: Patricia M.b. Saint-vincent, Garret Veloski, James I. Sams, Matthew D. Reeder, Mumbi Mundia-howe, Natalie J. PekneyAbstract:Hundreds of oil Wells were drilled along Oil Creek in Pennsylvania in the mid-1800s, birthing the modern oil industry. No longer in operation, many Wells are now classified as Abandoned, and, due to their age, their locations are either unknown or inaccurately recorded. These historic-well sites present environmental, safety, and economic concerns in the form of possible methane leaks and physical hazards. Airborne magnetic and LiDAR surveys were conducted in the Pioneer Run watershed in Oil Creek State Park to find Abandoned Wells in a historically significant but physically challenging location. Wells were drilled in this area prior to modern geolocation and legal documentation. Although a large number of old Wells were Abandoned summarily without remediation of the site, much of the land area within Oil Creek State Park is now covered in trees and dense underbrush, which can obscure wellheads. The thick vegetation and steep terrain limited the possibility of ground-based surveys to easily find well sites for methane emissions studies. The data from remote sensing surveys were used to corroborate potential well locations from historic maps and photographs. Potential well sites were verified in a ground-based field survey and monitored for methane emissions. Two historic photographs documenting oil activity in the late 1800s were georeferenced using a combination of magnetic and LiDAR data. LiDAR data, which were more useful in georeferencing and in field verification, identified 290 field locations in the Pioneer Run watershed, 86% of which were possible well sites. Sixty-two percent of the ground-verified Wells remained unplugged and comprised the majority of leaking Wells. The mean methane emissions factor for unplugged Wells was 0.027 ± 0.099 kg/day, lower than other Appalachian Basin methane emissions estimates. LiDAR was used for the first time, in combination with an airborne magnetic survey, to reveal underground oil industry features and inform well identification and remediation efforts in difficult-to-navigate regions. In the oldest oil fields, where well casing has been removed or wood conductor casing was installed, historic photographs provide additional lines of evidence for oil Wells where ground disturbances have concealed surface features. Identification of well sites is necessary for mitigation efforts, as unplugged Wells emit methane, a potent greenhouse gas.
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Historic and modern approaches for discovery of Abandoned Wells for methane emissions mitigation in Oil Creek State Park, Pennsylvania.
Journal of environmental management, 2020Co-Authors: Patricia M.b. Saint-vincent, Garret Veloski, James I. Sams, Matthew D. Reeder, Mumbi Mundia-howe, Natalie J. PekneyAbstract:Abstract Background Hundreds of oil Wells were drilled along Oil Creek in Pennsylvania in the mid-1800s, birthing the modern oil industry. No longer in operation, many Wells are now classified as Abandoned, and, due to their age, their locations are either unknown or inaccurately recorded. These historic well sites present environmental, safety, and economic concerns in the form of possible methane leaks and physical hazards. Methods Airborne magnetic and LiDAR surveys were conducted in the Pioneer Run watershed in Oil Creek State Park to find Abandoned Wells in a historically significant but physically challenging location. Wells were drilled in this area prior to modern geolocation and legal documentation. Although a large number of old Wells were Abandoned summarily without remediation of the site, much of the land area within Oil Creek State Park is now covered in trees and dense underbrush, which can obscure wellheads. The thick vegetation and steep terrain limited the possibility of ground-based surveys to easily find well sites for methane emissions studies. The data from remote sensing surveys were used to corroborate potential well locations from historic maps and photographs. Potential well sites were verified in a ground-based field survey and monitored for methane emissions. Results Two historic photographs documenting oil activity in the late 1800s were georeferenced using a combination of magnetic and LiDAR data. LiDAR data, which were more useful in georeferencing and in field verification, identified 290 field locations in the Pioneer Run watershed, 86% of which were possible well sites. Sixty-two percent of the ground-verified Wells remained unplugged and comprised the majority of leaking Wells. The mean methane emissions factor for unplugged Wells was 0.027 ± 0.099 kg/day, lower than other Appalachian Basin methane emissions estimates. Conclusions LiDAR was used for the first time, in combination with an airborne magnetic survey, to reveal underground oil industry features and inform well identification and remediation efforts in difficult-to-navigate regions. In the oldest oil fields, where well casing has been removed or wood conductor casing was installed, historic photographs provide additional lines of evidence for oil Wells where ground disturbances have concealed surface features. Identification of well sites is necessary for mitigation efforts, as unplugged Wells emit methane, a potent greenhouse gas.
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Measurement of methane emissions from Abandoned oil and gas Wells in Hillman State Park, Pennsylvania
Carbon Management, 2018Co-Authors: Natalie J. Pekney, J. Rodney Diehl, David Ruehl, James Sams, Garret Veloski, Adit Patel, Charles Schmidt, Thomas CardAbstract:Abandoned oil and gas Wells, improperly plugged or unplugged, present a risk to current and future oil and gas development because they provide a potential pathway for unwanted gas and fluid migration to the surface. The appropriate emission factor for gaseous emissions from these Wells is uncertain, as a limited number of studies have reported Abandoned Wells as a methane emissions source. A helicopter-based survey that mapped methane concentration and located Wells by detecting magnetic anomalies was conducted in Hillman State Park in southwestern Pennsylvania. Although well finding via aerial survey was successful, elevated methane concentrations due to emissions from Wells in the survey area were not detected by helicopter as Abandoned Wells were likely too small a source of methane to detect from elevations that helicopters fly at (tens of meters). Measurement of methane emission rates from 31 Wells were collected using several techniques that are compared and evaluated for their effectiveness: Hi Flow sampler, field-portable flame ionization detector, infrared camera, dynamic flux chamber and bag sampling. Nine of the 31 Wells were buried; average methane flux for these Wells was not statistically different from the background. Mass flow rate from the remaining 22 Wells ranged from non-detection (less than 0.09 kg CH4/day) to 4.18 kg CH4/day with a mean of 0.70 kg/well/day (median of 0.24 kg CH4/day/well) and a sample standard of error of 0.21 kg CH4/well/day. This emission factor, while not intended for exclusive use in developing a methane emissions inventory for Abandoned oil and gas Wells, contributes to the growing amount of methane emissions data for this source category. The results from the aerial survey, ground-based well location verification and emissions measurements, and the evaluation of measurement approaches described here, provide a comprehensive characterization of Abandoned Wells in one field that can inform future measurement studies.
Puran K. Sharma - One of the best experts on this subject based on the ideXlab platform.
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A malaria outbreak in Naxalbari, Darjeeling district, West Bengal, India, 2005: weaknesses in disease control, important risk factors.
Malaria Journal, 2009Co-Authors: Puran K. Sharma, Ramakrishnan Ramanchandran, Raju Sharma, Yvan Hutin, Mohan D. GupteAbstract:An outbreak of malaria in Naxalbari, West Bengal, India, in 2005 was investigated to understand determinants and propose control measures. Malaria cases were slide-confirmed. Methods included calculation of annual blood examination rates (ABER, number of slides examined/population), collection of water specimens from potential vector-breeding sites, sorting of villages in categories depending on the number of Abandoned Wells within two kilometers radius and review of the DDT spray coverage. Cases were compared with matched neighbourhood controls in terms of personal protection using matched odds ratios (MOR). 7,303 cases and 17 deaths were reported between April 2005 and March 2006 with a peak during October rains (Attack rate: 50 per 1,000, case fatality: 0.2%). The attack rate increased according to the number of Abandoned Wells within 2 kilometres radius (P < 0.0001, Chi-square for trend). Abandoned Wells were Anopheles breeding sites. Compared with controls, cases were more likely to sleep outdoors (MOR: 3.8) and less likely to use of mosquito nets and repellents (MOR: 0.3 and 0.1, respectively). DDT spray coverage and ABER were 39% and 3.5%, below the recommended 85% and 10%, respectively. Overall, this outbreak resulted from weaknesses in malaria control measures and a combination of factors, including vector breeding, low implementation of personal protection and weak case detection.
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A malaria outbreak in Naxalbari, Darjeeling district, West Bengal, India, 2005: weaknesses in disease control, important risk factors.
Malaria Journal, 2009Co-Authors: Puran K. Sharma, Ramakrishnan Ramanchandran, Raju Sharma, Yvan Hutin, Mohan D. GupteAbstract:An outbreak of malaria in Naxalbari, West Bengal, India, in 2005 was investigated to understand determinants and propose control measures. Malaria cases were slide-confirmed. Methods included calculation of annual blood examination rates (ABER, number of slides examined/population), collection of water specimens from potential vector-breeding sites, sorting of villages in categories depending on the number of Abandoned Wells within two kilometers radius and review of the DDT spray coverage. Cases were compared with matched neighbourhood controls in terms of personal protection using matched odds ratios (MOR). 7,303 cases and 17 deaths were reported between April 2005 and March 2006 with a peak during October rains (Attack rate: 50 per 1,000, case fatality: 0.2%). The attack rate increased according to the number of Abandoned Wells within 2 kilometres radius (P < 0.0001, Chi-square for trend). Abandoned Wells were Anopheles breeding sites. Compared with controls, cases were more likely to sleep outdoors (MOR: 3.8) and less likely to use of mosquito nets and repellents (MOR: 0.3 and 0.1, respectively). DDT spray coverage and ABER were 39% and 3.5%, below the recommended 85% and 10%, respectively. Overall, this outbreak resulted from weaknesses in malaria control measures and a combination of factors, including vector breeding, low implementation of personal protection and weak case detection.
Shigeru Saito - One of the best experts on this subject based on the ideXlab platform.
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The Long-term Corrosion Behavior of Abandoned Wells Under CO2 Geological Storage Conditions: (3) Assessment of Long-term (1,000-year) Performance of Abandoned Wells for Geological CO2 Storage☆
Energy Procedia, 2013Co-Authors: Kohei Yamaguchi, Satoko Shimoda, Hiroyasu Kato, Michael J. Stenhouse, Wei Zhou, Alexandros Papafotiou, Yuji Yamashita, Kazutoshi Miyashiro, Shigeru SaitoAbstract:Abstract A hypothetical CO 2 storage site that has some Abandoned Wells located near the injection well is considered. Generally, cement plugs are set to cover or isolate porous or productive formations and to isolate usable groundwater from hydrocarbons. When CO 2 is injected into a reservoir, supercritical CO 2 or dissolved CO 2 spreads out in the reservoir. This dissolved CO 2 can react chemically with cement seals (plugs and casing cement) in Abandoned Wells. As a result, minerals in the cement seals (plugs and casing cement) may alter to form other minerals or mineral phases. The first simulations concerning migration of supercritical CO 2 and dissolved CO 2 in a saline aquifer and a depleted gas field reservoir, were carried out using TOUGH2. The following temperatures and depths of reservoir were selected: 50 °C at E.L.-1,000 m, 60 °C at E.L.-1,500 m and 70 °C at E.L.-2,000 m. Secondly, geochemical reactions of cement seals (plugs and casing cement) were simulated. The results of reservoir simulations were used as boundary conditions for the geochemical calculation of cement seals. Geochemical simulation of the reactions yielded the extent (length) of alteration of cement seals (plugs and casing cement) after long time periods; for example, the alteration length of cement seals after 1,000 years was about one meter. This length is short enough so that the usable cement seals (plugs and casing cement) of Abandoned well are able to continue to isolate CO 2 in the reservoir from the upper aquifer.
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The Long-term Corrosion Behavior of Abandoned Wells Under CO2 Geological Storage Conditions: (1) Experimental Results for Cement Alteration☆
Energy Procedia, 2013Co-Authors: Hisao Satoh, Kohei Yamaguchi, Satoko Shimoda, Hiroyasu Kato, Yuji Yamashita, Kazutoshi Miyashiro, Shigeru SaitoAbstract:For a feasible risk assessment of CO2-leakage through Wells of the carbon dioxide storage sites at Abandoned Wells of aquifers and depleted gas fields, the CO2 reactivity and permeability of casing steel, pseudo formation and cement- plug need to be evaluated experimentally as functions of temperature, pressure and formation water chemistry to provide fundamental information for the assessment. Two types of laboratory experiments were conducted. These experiments are shown below: (1) Conventional batch-reaction experiments of cement cores in the system of CO2 and simulated formation water as 0.5 M NaCl, at 50 and 70 C, 5, 8, 18 MPa for 100-1600hr. In this experiment, individual cement cores are allowed to react with wet CO2 and NaCl solution charged in titanium reaction vessels with PTFE separators. (2) CO2-injection reaction involving casing (API Grade J-55)-cement (API class A) and cement (API class A)-shale composites which were saturated with 0.5 M NaCl solution. As a counter experiment for batch experiments, zero CO2 runs for these cements were additionally carried out at 50 and 70 C at 5 MPa for 100 and 400 hr. The CO2-injection runs were carried out at 50 C and 8.5 MPa with a constant differential pressure of 5 kPa. The resultant products were used to analyze alteration depth via micro-focused X-ray computed tomography (-XCT) and electron probe micro analyzer (EPMA). For observation and determination of alteration phases, field mission scanning electron microscopy with energy dispersive spectroscopy (FESEM-EDS) and micro X-ray diffractometry (-XRD) were also performed. The alteration zones identified in the both cement cores of A and G in wet CO2 showed spatial developments of zones appearing in -XCT images as a function of square root of time (t1/2), which can be interpreted as a diffusion-limited reaction. However, in the NaCl solution, these cement cores developed little alteration zones and poorly displayed time-dependency after 100 h.
