The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Reinout Heijungs - One of the best experts on this subject based on the ideXlab platform.
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abiotic resource depletion potentials adps for elements revisited updating ultimate reserve estimates and introducing time series for Production data
International Journal of Life Cycle Assessment, 2020Co-Authors: Lauran Van Oers, Jeroen B Guinee, Reinout HeijungsAbstract:In 1995, the original method for assessing the impact category abiotic resource depletion using abiotic depletion potentials (ADPs) was published. The ADP of a resource was defined as the ratio of the annual Production and the square of the ultimate (crustal content based) reserve for the resource divided by the same ratio for a reference resource (antimony (Sb)). In 2002, ADPs were updated based on the most recent USGS annual Production data. In addition, the impact category was sub-divided into two categories, using two sets of ADPs: the ADP for fossil fuels and the ADP for elements; in this article, we focus on the ADP for elements. Since then, ADP values have not been updated anymore despite the availability of updates of annual Production data and also updates of crustal content data that constitute the basis of the ultimate reserves. Moreover, it was known that the coverage of elements by ADPs was incomplete. These three aspects together can affect relative ranking of abiotic resources based on the ADP. Furthermore, dealing with annually changing Production data might have to be revisited by proposing new calculation procedures. Finally, category totals to calculate normalized indicator results have to be updated as well, because incomplete coverage of elements can lead to biased results. We used updated reserve estimates and time series of Production data from authoritative sources to calculate ADPs for different years. We also explored the use of several variations: moving averages and Cumulative Production data. We analyzed the patterns in ADP over time and the contribution by different elements in the category total. Furthermore, two case studies are carried out applying two different normalization reference areas (the EU 27 as normalization reference area and the world) for 2010. We present the results of the data updates and improved coverage. On top of this, new calculation procedures are proposed for ADPs, dealing with the annually changing Production data. The case studies show that the improvements of data and calculation procedures will change the normalized indicator results of many case studies considerably, making ADP less sensitive for fluctuating Production data in the future. The update of ultimate reserve and Production data and the revision of calculation procedures of ADPs and category totals have resulted in an improved, up-to-date, and more complete set of ADPs and a category total that better reflects the total resource depletion magnitude than before. An ADP based on the Cumulative Production overall years is most in line with the intent of the original ADP method. We further recommend to only use category totals based on Production data for the same year as is used for the other (emission-based) impact categories.
Xiang Ding - One of the best experts on this subject based on the ideXlab platform.
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modelling of time dependent proppant embedment and its influence on tight gas Production
Journal of Natural Gas Science and Engineering, 2020Co-Authors: Xiang Ding, Fan Zhang, Guangqing ZhangAbstract:Abstract Hydraulic fracturing is typically used to exploit underground gas/oil resources. However, most commercial fracture-design programs and reservoir simulators neglect proppant embedment issues when calculating hydraulic the fracture width, and the majority of previous studies regarding proppant embedment treat the reservoir rocks as time-independent materials–elastic or elastoplastic. In this study, the time dependent deformation of tight reservoir rocks is validated through laboratory experiments, and the fractional Maxwell model is utilized to characterize the viscoelastic deformation of tight sandstones. Combining the fractional rheological model with the Hertz contact theory, an analytical model of fracture width, which considers the time-dependent embedment depth of proppants, is established. Utilizing this analytical model of fracture width, numerical simulations are conducted to study the viscoelastic deformation of tight sandstones on the long-term acCumulative Production of tight gas. Numerical simulations of a fifteen-year Cumulative Production tight gas well indicate the long-term gas Production, which considers the creep characteristics of a tight sandstone reservoir, experiences a 40 % reduction when compared to the Production of a linear elastic reservoir. Therefore, consideration of the viscoelastic characteristics of reservoir rocks to predict the long-term oil/gas Production is extremely significant.
Tadeusz W Patzek - One of the best experts on this subject based on the ideXlab platform.
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the effect of natural fracture s closure on long term gas Production from unconventional resources
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Umut Aybar, Mohammad O. Eshkalak, Kamy Sepehrnoori, Tadeusz W PatzekAbstract:Abstract The future U.S. and world energy supply is supported by the observed trends of long-term Production forecasts from unconventional resources. Also, recent innovations in multi-pad horizontal drilling and hydraulic fracturing empower such trends to be economically viable. Nevertheless, the triggered fractures in an unconventional reservoir rapidly shrink, as a result of produced gas that leads to a significant loss in long-term Production. Hence, it is critical to quantify the effect of fracture closure on long-term Production for to reach an accurate Production forecast. In this paper, the permeability changes of secondary fractures network are investigated with respect to their effect on the long-term gas Production from unconventional resources. An analytical trilinear model is revised and improved in order to handle the constant bottom-hole pressure Production scenario and hence analyzing the Cumulative gas Production by considering the effect of stress on natural fracture permeability. In addition, a comprehensive sensitivity study is performed to rank the influence of uncertain parameters on Cumulative Production and consequently identify a condition in which a severe effect of pressure-dependent natural fracture on Production is observed. It is concluded that the pressure-dependent natural fracture permeability can cause up to ten percent less Cumulative Production than considering the constant natural fracture permeability. Also, the improved analytical model is very fast and robust compared to the commercial numerical simulators. The advantage of this approach is to obtain a quick and accurate assessment of the complex Production behavior of unconventional reservoirs. The findings of this paper provide valuable insights into long-term investment on unconventional reservoirs and guide decision making for the secondary or tertiary enhancement treatments of unconventional wells, such as re-fracturing.
Lauran Van Oers - One of the best experts on this subject based on the ideXlab platform.
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abiotic resource depletion potentials adps for elements revisited updating ultimate reserve estimates and introducing time series for Production data
International Journal of Life Cycle Assessment, 2020Co-Authors: Lauran Van Oers, Jeroen B Guinee, Reinout HeijungsAbstract:In 1995, the original method for assessing the impact category abiotic resource depletion using abiotic depletion potentials (ADPs) was published. The ADP of a resource was defined as the ratio of the annual Production and the square of the ultimate (crustal content based) reserve for the resource divided by the same ratio for a reference resource (antimony (Sb)). In 2002, ADPs were updated based on the most recent USGS annual Production data. In addition, the impact category was sub-divided into two categories, using two sets of ADPs: the ADP for fossil fuels and the ADP for elements; in this article, we focus on the ADP for elements. Since then, ADP values have not been updated anymore despite the availability of updates of annual Production data and also updates of crustal content data that constitute the basis of the ultimate reserves. Moreover, it was known that the coverage of elements by ADPs was incomplete. These three aspects together can affect relative ranking of abiotic resources based on the ADP. Furthermore, dealing with annually changing Production data might have to be revisited by proposing new calculation procedures. Finally, category totals to calculate normalized indicator results have to be updated as well, because incomplete coverage of elements can lead to biased results. We used updated reserve estimates and time series of Production data from authoritative sources to calculate ADPs for different years. We also explored the use of several variations: moving averages and Cumulative Production data. We analyzed the patterns in ADP over time and the contribution by different elements in the category total. Furthermore, two case studies are carried out applying two different normalization reference areas (the EU 27 as normalization reference area and the world) for 2010. We present the results of the data updates and improved coverage. On top of this, new calculation procedures are proposed for ADPs, dealing with the annually changing Production data. The case studies show that the improvements of data and calculation procedures will change the normalized indicator results of many case studies considerably, making ADP less sensitive for fluctuating Production data in the future. The update of ultimate reserve and Production data and the revision of calculation procedures of ADPs and category totals have resulted in an improved, up-to-date, and more complete set of ADPs and a category total that better reflects the total resource depletion magnitude than before. An ADP based on the Cumulative Production overall years is most in line with the intent of the original ADP method. We further recommend to only use category totals based on Production data for the same year as is used for the other (emission-based) impact categories.
Josep Peñuelas - One of the best experts on this subject based on the ideXlab platform.
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Rice straw incorporation affects global warming potential differently in early vs. late cropping seasons in Southeastern China
Field Crops Research, 2015Co-Authors: Weiqi Wang, Derrick Y. F. Lai, Jordi Sardans, Chun Wang, Arindam Datta, Ting Pan, Congsheng Zeng, Mireia Bartrons, Josep PeñuelasAbstract:Abstract Paddy fields are a major global anthropogenic source of methane (CH4) and nitrous oxide (N2O), which are very potent greenhouse gases. China has the second largest area under rice cultivation, so developing valid and reliable methods for reducing emissions of greenhouse gases while sustaining crop productivity in paddy fields is of paramount importance. We examined the effects of applying straw, a residual product of rice cultivation containing high amounts of carbon and nutrients, to rice crops during both an early crop season (5 April – 25 July 2012) and a late crop season (1 August – 6 November 2012) on CH4 and N2O emissions in a subtropical paddy field in southeastern China. CH4 fluxes had two seasonal peaks, on 5 May and 28 June, in the early crop but only one peak, on 13 August, in the late crop, which could be attributed to the lower temperatures after the final tillering stage in the late crop. Straw application significantly increased mean CH4 Cumulative Production (g m−2) relative to the control in the late crop (37.3 vs. 8.34 mg m−2, P 0.05). The application of straw significantly increased N2O Cumulative Production relative to the control in the late crop (75.9 vs. 43.4 μg m−2 h−1) but decreased N2O Cumulative Production by over 43% in the early crop (15.60 vs. 27.27 μg m−2 h−1) (P
