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1
Yuan, Yingzhong, Zhilin Qi, Zhangxing Chen, Wende Yan e Zhiheng Zhao. "Production decline analysis of shale gas based on a probability density distribution function". Journal of Geophysics and Engineering 17, n. 2 (10 febbraio 2020): 365–76. http://dx.doi.org/10.1093/jge/gxz122.
Testo completoAbstract (sommario):
Abstract Production decline analysis is a simple and efficient method to forecast production dynamics of shale gas. The traditional Arps decline model is also widely used in the production decline analysis of shale gas, but an obvious error is often generated. Based on the Weibull and χ2 probability density distribution function, the monotonic decreasing production prediction equations of shale gas are established. It is deduced that recently, the widely used Duong model is essentially a Weibull probability density distribution model. Decline analysis results of production data from actual shale gas well and numerical simulations indicate that the fitting results of the Weibull (Duong) model and χ2 distribution model are better than the Arps model whose deviation of early data is large. For a shale gas reservoir with very low permeability, pressure conformance area is small and it is obviously influenced by fractures. Early shale gas production rate mainly contributed to by fractures declines quickly and the later production rate mainly contributed to by the matrix declines slowly over time. The production decline curve has obvious long-tail distribution characteristics and it is a better fit to the data with a χ2 distribution model. As for the increase of permeability, the fitting accuracy of the Weibull (Duong) model gradually becomes better than the χ2 distribution model. Research results provide theoretical guidance for choosing a reasonable production decline model of a shale gas reservoir with a different permeability.
2
Denney, Dennis. "Relationship of Decline Analysis to Relative Permeability". Journal of Petroleum Technology 51, n. 01 (1 gennaio 1999): 44–45. http://dx.doi.org/10.2118/0199-0044-jpt.
Testo completo
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Tan, Yunhui, Yan Li, Margaretha C. M. Rijken, Karim Zaki, Bin Wang, Ruiting Wu, Oya Karazincir e Wade Williams. "Modeling of Production Decline Caused by Fines Migration in Deepwater Reservoirs". SPE Journal 25, n. 01 (13 agosto 2019): 391–405. http://dx.doi.org/10.2118/187263-pa.
Testo completoAbstract (sommario):
Summary Many deepwater wells experience steep productivity declines. Some field observations indicate that this decline is partly attributable to fines-migration effects. In this paper, we present a numerical workflow to simulate the effect (over time) of flow-induced fines migration on production decline in deepwater reservoirs. A permeability-reduction function was extracted from long-term coreflood tests and implemented into a reservoir simulator. Using the permeability-reduction function, production degradation caused by fines migration was simulated in a detailed single-well model. From previous research, it was understood that fines migration does not start until the flow velocity is greater than the critical velocity. After many long-term coreflood tests, or extended fines-migration (EFM) tests, we concluded that the permeability damage induced by fines migration is a function of the pore-volume (PV) throughput (fluid volume flowing through the core divided by the PV of the core). To address these observations, the numerical model was updated such that the interstitial flow velocity was tracked in each individual cell. When the interstitial velocity is greater than the critical velocity, the cell's permeability follows the permeability-reduction trend obtained from laboratory data. Validation of the workflow is performed using a cylinder model to match the laboratory test core-plug data. A detailed 3D model was constructed to study the fines-migration effect in each part of the near-wellbore (e.g., perforation, fracture) region and the reservoir. As expected, fines migration started near the perforation where the flow velocity was the highest. Depending on the permeability-decline rate, the production asymptotes eventually reached a constant value after a certain period. Both the decline rate and the ultimate residual permeability had a strong effect on the final production. Sensitivities were run to study the effect of fines migration in different completions. To the authors’ understanding, this is the first time that laboratory-based fines-migration data were incorporated into a reservoir simulator to predict the production decline using experiment-based fines-migration functions. This workflow will help reservoir engineers predict the damage caused by fines migration, predict production decline, and plan for remediation.
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Russell, Thomas, Larissa Chequer, Alexander Badalyan, Zhenjiang You e Pavel Bedrikovetsky. "Effect of kaolinite content on formation damage due to fines migration: systematic laboratory and modelling study". APPEA Journal 58, n. 2 (2018): 743. http://dx.doi.org/10.1071/aj17189.
Testo completoAbstract (sommario):
Laboratory tests have been done to investigate the effect of kaolinite content on the behaviour of unconsolidated sandstone rocks during the injection of low-salinity water. Artificial cores comprised of kaolinite and chemically washed sand were prepared and compacted for this study. Five cores with kaolinite weight percentages ranging from 1% to 10% were injected sequentially with sodium chloride solutions of stepwise decreasing salinity. The permeability of the cores declined to as little as 1/54 times the initial permeability. Negligible permeability decline was observed when the kaolinite content was only 1% of the total mass. Generally, the extent of permeability decline was greater in cores with a larger percentage of kaolinite. The results are explained by the effect of kaolinite not only on the abundance of detachable clays, but also on the pore size. The results from the laboratory test were fitted with an exact solution of a model for fines migration. The parameters from these tests were input into a model for radial injection of low-salinity water to predict the extent of injectivity decline. The results serve as a benchmark for correlating injectivity decline due to fines migration between wells using the rock mineralogy. The tests suggest that mineralogy alone is not sufficient to fully predict formation damage, and that pore geometry and the nature of particle detachment are still critical factors for this process.
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Zhang, Zhang, Shun Li He, Hai Yong Zhang, Shao Yuan Mo e Shuai Li. "Decline Curves of a Vertical Well in Stress-Sensitive Reservoir". Advanced Materials Research 772 (settembre 2013): 781–88. http://dx.doi.org/10.4028/www.scientific.net/amr.772.781.
Testo completoAbstract (sommario):
Stress-sensitivity effects have been recognized to have impact on the pressure/rate transient behavior of wells in several reservoirs. Although the effects of stress-sensitivity have been considered in well testing theory in the past thirty years, little has been done to determine their influence on rate decline behavior. This paper presents a single phase flow model considering stress-sensitive formation permeability to investigate the characteristic of production rate decline of a vertical well. The stress-sensitive permeability is considered as an exponential form. The permeability changes with pressure drop are described by a permeability modulus. By introducing two pseudo functions, the equations of the mathematical model are linearized and approximate semi-analytical solutions are obtained. The analytical solutions are carefully verified through numerical simulation. Two sets of new decline type curves are diagramed on a log-log plot for constant rate case and constant bottomhole pressure case respectively. The influence of stress-sensitive permeability on decline curves are analyzed and compared. From this work, we recognized that the rate decline characteristics of stress-sensitive reservoir under constant rate and constant bottomhole producing condition are different. New analysis method should be developed to analyze field variable rate/variable pressure drop data.
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Machenbach, I., T. Leiknes e H. Ødegaard. "Coagulation/submerged hollow-fibre ultrafiltration for natural organic matter removal". Water Supply 3, n. 5-6 (1 dicembre 2003): 401–7. http://dx.doi.org/10.2166/ws.2003.0195.
Testo completoAbstract (sommario):
Experiments were carried out to investigate the removal of humic substances from highly coloured raw water (50 mg Pt/L) by coagulation and outside-in hollow-fibre membrane filtration. Chitosan, a cationic biopolymer produced from crustacean shells, and polyaluminium chloride (PACl) were used as coagulants. The rate of permeability decline was determined for different backwash frequencies and different fluxes at a 95% water recovery of the membrane. Coagulation with PACl gave a good and consistent permeate quality with removals of 95.6%, 84.9%, and 66.1% for true colour, UV absorbers, and dissolved organic carbon, respectively. Longer filtration intervals with less frequent backwashing as well as lower specific aluminium dosages increased the rate of permeability decline. The particle size distribution in the retentate tank was not affected by the frequency of backwashing. Chitosan was less effective in coagulating humic substances and the removal efficiencies were notably lower. Preliminary results suggest that the permeability declines somewhat faster for chitosan compared to PACl-coagulated water.
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Kimura, Katsuki, Naoko Ogawa e Yoshimasa Watanabe. "Permeability decline in nanofiltration/reverse osmosis membranes fed with municipal wastewater treated by a membrane bioreactor". Water Science and Technology 67, n. 9 (1 maggio 2013): 1994–99. http://dx.doi.org/10.2166/wst.2013.080.
Testo completoAbstract (sommario):
Decline in the permeability in nanofiltration (NF)/reverse osmosis (RO) membranes that filtered effluents from a membrane bioreactor (MBR) treating municipal wastewater was investigated in this study. Four different 2-inch spiral-wound NF/RO membrane elements were continuously operated for 40 days. The results showed that the amount of deposits on the membrane surface did not affect the degree of permeability decline. Laboratory-scale filtration tests with coupons obtained from the fouled membranes also revealed that the contribution of the gel/cake layer to total filtration resistance was minor. Rather, constituents that were strongly bound to the membranes were mainly responsible for permeability decline. Chemical cleaning of the fouled membranes carried out after removal of the cake showed that silica played an important role in the decline in permeability. A considerable amount of organic matter which was mainly composed of carbohydrates and proteins was also desorbed from the fouled membranes.
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Li, Chen, e Sheng Ling Xiao. "A Comparative Analysis of the Performance of PVC Film Aging by Ultraviolet and Thermal Methods". Advanced Materials Research 830 (ottobre 2013): 45–48. http://dx.doi.org/10.4028/www.scientific.net/amr.830.45.
Testo completoAbstract (sommario):
In this article, the changes of the polyvinyl chloride (PVC) film properties and its law are analyzed during the ultraviolet and thermal aging. Using accelerated aging methods in laboratory,it was found that the tensile strength by ultraviolet aging fell down, on the contrary, it raised by thermal aging. This result indicate that PVC film was not aged to reduce the tensile strength at 50°C for 120h.We found the air permeability curves rose firstly then to decline, and the moisture permeability of PVC film curves declined by the two aging methods. The effects of the ultraviolet aging on the air and moisture permeability were a marked decrease.
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Shen, Yinghao, Xinyu Yang e Yuelei Zhang. "Production Analysis of Tight Sandstone Reservoir in Consideration of Stress-Sensitive Permeability". Open Petroleum Engineering Journal 10, n. 1 (28 aprile 2017): 82–93. http://dx.doi.org/10.2174/1874834101710010082.
Testo completoAbstract (sommario):
Background: Tight sandstone reservoirs play an important role in the oil industry. The permeability of tight sandstone reservoir generally has stronger stress sensitivity than that of conventional reservoir because of the latter’s poor physical properties. However, the production analysis of tight sandstone reservoir did not fully considered the stress-sensitive permeability yet. Objective: This paper proposed a production analysis method considering the stress- sensitive permeability. Method: This paper firtstly investigated the stress sensitivity characteristics and the effect of stress-sensitive permeability on a tight reservoir. Decline-type curves that consider stress-sensitive permeability are then established, and a systematic analysis method was built for the production analysis to obtain the single-well controlled dynamic reserves and reservoir physical properties. Results: A field analysis was performed in combination with Block Yuan-284 of Changqing Oilfield. Results show that with the reduction of reservoir pressure, stress sensitivity leads to the decline in reservoir permeability and the increase in seepage resistance, thus reducing the actual single-well controlled reserve and radius. Conclusion: By utilizing the analysis method based on the decline curves, we can effectively predict the single-well controlled dynamic reserves of such reservoirs and evaluate the characteristic parameters of reservoirs.
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Yan, Qing Hui, Han Min Xiao, Ling Hui Sun, Wei Dong Liu e Jun Cheng Hu. "Study on the Features of Production Decline Law in Oil Manufacturing System in Wangyao Block". Applied Mechanics and Materials 252 (dicembre 2012): 388–93. http://dx.doi.org/10.4028/www.scientific.net/amm.252.388.
Testo completoAbstract (sommario):
Features of production decling determines the deployment of development project in oilfield, which has heavy influence on the oil manufacturing system. Eq.(17)and (18) have shown the final results. The characteristics of oil and water percolation, presented by Figure.1, are the primary factors for decline law. Oil-water relative permeability equations of WangYao Block, in AnSai oilfield, was deducted, and the oil-water relative permeability curves were drawn according to the equations. The oil phase curve presents a change from a linear relationship to an exponential relationship with the increase of the water saturation, which means an exponential decrease and a harmonic decrease of the single well production.
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Gao, Changhong. "Simulation of reservoir permeability decline due to invasion of large particles". APPEA Journal 48, n. 1 (2008): 1. http://dx.doi.org/10.1071/aj07001.
Testo completoAbstract (sommario):
Particles can deposit in reservoir rocks and cause severe damage to their permeabilities. The mechanisms of permeability decline are attributed to adsorption, size exclusion and gravity settling of particles in porous media. Previous test results reveal that high particle concentration, low fluid velocity, large particle size lead to more damage. Traditional models are empirical correlations heavily dependent on core test data. In this paper, a network model incorporating the damaging mechanisms is used to study capture of large (non-Brownian) particles in porous media and resultant permeability damage. The model employs certain assumptions to imitate the characteristics of real porous media. The proposed procedure applies force analysis to obtain particle invasion depth, and determines damaging mechanisms by pore size to particle size ratio. The model assumes that for a particle much smaller than the pore where it is captured, surface deposition is the mechanism for permeability decline. For particle size comparable to pore size, pore throat plugging and bridging are the causes of permeability damage. The method is validated with test data and reasonably good results are obtained. The new model provides more insights into the deposition process and does not rely on core flooding data.
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Xu, Jian, Chang Ren, Songhe Wang, Jingyu Gao e Xiangang Zhou. "Permeability and Microstructure of a Saline Intact Loess after Dry-Wet Cycles". Advances in Civil Engineering 2021 (10 marzo 2021): 1–18. http://dx.doi.org/10.1155/2021/6653697.
Testo completoAbstract (sommario):
Influenced by both dry-wet cycles and salt weathering, the loess will exhibit significant changes in microstructure and permeability, which threatens the stability of loess slopes. Triaxial permeability tests and industrial computed tomography (CT) scans were carried out on saline intact loess with sodium sulfate. The relationship between permeability and pore structure of the loess after dry-wet cycles was discussed. Results show that the permeability coefficient of loess increases after dry-wet cycles, with the increment declining. After specified dry-wet cycles, the permeability coefficient increases approximately linearly with sodium sulfate content. However, the permeability coefficient significantly declines at higher confining pressures, while its attenuation rate decreases. An empirical relationship based on log 10 1 + e − log 10 k was proposed to estimate the permeability coefficient of saline intact loess considering dry-wet cycles and salt content. Comparisons of measured and calculated results proved its rationality. CT scan images imply the damage to soil microstructure induced by dry-wet cycles and salt weathering, corresponding to the decline of the mean CT value (ME) and the increase of both crack ratio and fractal dimension of crack network.
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Yang, Z., D. Tamhane, A. K. Khurana, D. G. Crosby e M. Jones. "RETROGRADE CONDENSATION OR WATER IMBIBITION ? A CASE STUDY OF GAS WELL PRODUCTIVITY DECLINE BEFORE AND AFTER HYDRAULIC FRACTURING". APPEA Journal 36, n. 1 (1996): 562. http://dx.doi.org/10.1071/aj95034.
Testo completoAbstract (sommario):
Studies have been carried out to diagnose the cause of productivity decline for the Kaimiro-1 well in the Kaimiro gas field, Taranaki Basin, New Zealand. The gas flow rate for Kaimiro-1, declined from 5 MMSCFD (0.14 Mm3 per day) in 1983 to about 0.6 MMSCFD (0.017 Mm3 per day) in 1993, immediately prior to hydraulic fracturing. While hydraulic fracturing initially increased production rates, long term post-fracture results have been disappointing. The volumetric gas-in-place for the field was estimated to be at least 100 BCF (2.83 Gm3), whereas the total cumulative gas recovery to date is 5.1 BCF (0.14 Gm3). During the production period prior to hydraulic fracturing, reservoir pressure declined from an initial 6,109 psi to 5,625 psi (42.1 MPa to 38.8 MPa). The well has produced water at low rates over its entire production history. Analysis of pressure build-up data showed a continued decline trend in effective reservoir permeability with time. Thus, it appeal s that the productivity decline is due to a decrease in effective permeability to gas and not to natural depletion. However, the exact origin of this decrease in effective permeability has been the subject of much controversy. Two competing theories regarding the decrease in permeabiiity have been proposed: retrograde condensation and water imbibition. Based on black oil and compositional simulation studies of pre-and post-fracture production, together with hindsight analysis of hydraulic fracturing, it is concluded that retrograde condensation is more likely to be the primary cause of productivity decline.
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Wang, Z. Z., T. Zsirai, K. Connery, M. Fabiyi, A. Larrea, J. Li e S. J. Judd. "Biomass properties and permeability in an immersed hollow fibre membrane bioreactor at high sludge concentrations". Water Science and Technology 69, n. 11 (28 marzo 2014): 2324–30. http://dx.doi.org/10.2166/wst.2014.142.
Testo completoAbstract (sommario):
This study aimed to investigate the influence of biomass properties and high mixed liquor suspended solids (MLSS) concentrations on membrane permeability in a pilot-scale hollow fibre membrane bioreactor treating domestic wastewater. Auxiliary molasses solution was added to maintain system operation at constant food-to-microorganisms ratio (F/M = 0.13). Various physicochemical and biological biomass parameters were measured throughout the trial, comprising pre-thickening, thickening and post-thickening periods with reference to the sludge concentration and with aerobic biotreatment continuing throughout. Correlations between dynamic changes in biomass characteristics and membrane permeability decline as well as permeability recovery were further assessed by statistical analyses. Results showed the MLSS concentration to exert the greatest influence on sustainable membrane permeability, with a weaker correlation with particle size distribution. The strong dependence of absolute recovered permeability on wet accumulated solids (WACS) concentration, or clogging propensity, revealed clogging to deleteriously affect membrane permeability decline and recovery (from mechanical declogging and chemical cleaning), with WACS levels increasing with increasing MLSS. Evidence from the study indicated clogging may permanently reduce membrane permeability post declogging and chemical cleaning, corroborating previously reported findings.
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Wang, Yi Ning, Xiao Dong Wu, Rui He Wang, Feng Peng Lai, Bei Lin Qi e Zhuang Zhang. "Study on the Production Decline Laws for Vertical Fracture Well in Low-Permeability Gas Reservoirs". Applied Mechanics and Materials 527 (febbraio 2014): 81–87. http://dx.doi.org/10.4028/www.scientific.net/amm.527.81.
Testo completoAbstract (sommario):
The vertical fracture was asymmetrical about the wellbore or two wings of a fracture are not certainly in a line for the complex geo-stress in the possession of fracturing of the gas reservoirs. In view of the low permeability reservoir after fracturing developing the asymmetrical vertical fracture and non-coplanar fractures, based on the non-steady seepage theory, using the potential function theory, superimposition principle and numerical analysis method, a performance prediction model for the vertical fracture in low-permeability gas reservoirs was deduced with pressure drop superposition principle. The production decline laws were analyzed by practical cases. The result shows that the initial production of the vertical fracture is relatively high but soon followed by a sharp decline. Then, the production keeps in a relatively stable state and declines slowly in the middle and later. The fracture asymmetry factor has little effect on the gas well productivity. The non-coplanar angles have greater effect on the oil well productivity in the initial stage. The more the fracture length and the bigger the flow conductivity, the higher the oil well production and the faster the decline rate will be. However, the increase amplitude will be getting smaller and smaller along with the fracture length and flow conductivity.
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Masoner, Lance O. "A Decline-Analysis Technique Incorporating Corrections for Total Fluid-Rate Changes". SPE Reservoir Evaluation & Engineering 2, n. 06 (1 dicembre 1999): 533–41. http://dx.doi.org/10.2118/59474-pa.
Testo completoAbstract (sommario):
Summary Decline analysis inherently assumes a constant total-reservoir-fluid rate in contrast to constantly varying rates in actual field operations. This paper provides an approach for determining decline constants under varying total fluid rates for secondary or tertiary oil recovery processes. It further enables forecasting oil and nonoil production performance under different total fluid rate strategies. The technique helps identify pseudosteady state flow periods when decline analysis techniques are valid. It distinguishes incremental from accelerated oil responses when a recovery process change, operating practices, or workover activity causes a total fluid rate change. Introduction Decline analysis forms a very useful tool for extrapolating oil production into the future. The recovery of oil can be defined in terms of three basic parameters: the oil relative permeability, the drainage volume, and the pressure gradient. Problems arise in using decline analysis when changes to the relative permeability relationship or apparent drainage volume occur. The reservoir is said to be in transition during the period of changing drainage volume or relative permeability relationship (the latter induced by changes in recovery mechanism). Decline analysis is not appropriate during transition periods. However, decline analysis can incorporate corrections for changes in the pressure gradient. Pressure gradient changes result from many actions taken during production operations. These include reservoir pressure changes associated with pressure depletion under primary recovery, pressure increases resulting from secondary and tertiary fluid injection, and other voidage replacement practices. Pressure gradient changes also result from bottom hole producing pressures (or back pressure) associated with well flowing conditions, pump changes, pump efficiency losses, wellbore stimulations, and temporary shut ins. Pressure gradient changes are generally revealed as total fluid rate changes. A decline analysis procedure correcting for pressure gradient or total reservoir fluid rate (referred to here as the processing rate) changes during secondary and tertiary recovery addresses many common situations. Injection in excess of withdrawals can result in increasing reservoir pressure and in turn a period of increasing oil production making conventional decline analysis inappropriate. During postmortem workover and in-fill drilling analysis, such a method can provide the distinction between accelerated and incremental oil responses since acceleration manifests itself as an increase in the pressure gradient. A base production forecast is often used to calculate an incremental response from an operational change. Correcting the extrapolated base performance for changes in the actual total fluid rate is essential in determining the technical incremental oil response; an accurate technical incremental response enhances the quality of project management decisions such as under CO2 flooding. The example of Fig. 1 demonstrates some of the utility of the processing-rate-corrected-decline method of this paper. The decline constants were obtained by matching the performance over the history match period shown. The deviation of the actual performance from the conventional exponential semilog straight-line decline fit resulted from increasing the injection rate and in turn the processing rate. The processing rate correction matches this along with most of the other fluctuations in the actual oil rate. The split between the actual and processing rate corrected curves resulted from a change in the recovery mechanism from waterflood to CO2 Because the method handles processing rate changes, both an economic and technical incremental oil response can be ascertained. The literature offers several methods for handling processing rate or pressure gradient changes. Fetkovich1 provides a solution for changing back pressure using superposition in conjunction with decline type curves for undersaturated single phase flow and constant productivity index and drainage radius. Fetkovich et al.2 use superposition but extend it for solution gas drive. Blasingame, McCray, and Lee3 provide four different superposition approaches that yield an equivalent time for use with decline type curves. Fetkovich4 also proposes use of rate normalization during transient production when both the rate and bottom hole flowing pressure are declining smoothly. These approaches were formulated for conditions of constant wellbore pressure with depleting reservoir pressure (changing pressure gradient) assuming single phase flow (oil relative permeability remains constant). These solutions are not applicable to secondary or tertiary recovery processes characterized by changing pressure gradients and multiphase flow. The empirically derived Arps5,6 decline equations successfully apply to several physically induced oil rate decline conditions. Fetkovich1,2,4,7,8 derived the exponential and hyperbolic decline form of Arps' equations based on pressure depletion as the cause of declining oil production. Matthews and Lefkovits9 extended pressure depletion to gravity drainage. Oil also declines in an exponential or hyperbolic fashion due to declining oil relative permeability associated with depleting oil saturation as derived by Masoner.10 The technique presented in this paper addresses decline analysis under conditions of changing pressure gradients (processing rates) for reservoirs under multiphase flow where the oil relative permeability dominates the decline; these conditions occur under solution gas drive, secondary, and tertiary recovery methods. This paper develops the theoretical basis for the processing rate correction to decline analysis; describes how the approach can significantly improve the accuracy and flexibility of decline analysis; presents examples for both water and CO2flooding, in-fill drilling, and stimulations; and provides insights on use of the technique for increasing flood performance understanding. Theoretical Development This section develops relationships and equations for processing rate correcting decline analysis. It begins with the discussion of a series of assumptions in which the relative permeability link to oil decline forms the key. Two different mathematical approaches to solve the problem are then presented for the special case of waterflooding: constant-ultimate-reserves method, and fluid-cut-maturity method. The fluid-cut-maturity method is further generalized for any immiscible multiphase recovery mechanism.
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Hagmeyer, G., e R. Gimbel. "Fouling of ultrafiltration membranes in drinking water treatment of karstic spring waters". Water Supply 1, n. 5-6 (1 giugno 2001): 277–83. http://dx.doi.org/10.2166/ws.2001.0124.
Testo completoAbstract (sommario):
Three UF-systems were tested for the drinking water treatment of karstic spring water. The pilot plants were operated in Marmagen, which is located in North-Rhine Westfalia (Germany). One of the two tested capillary UF-systems (in-out mode) was backflushed with filtrate and with filtrate and hydrogen peroxide. The other one could be flushed with air and raw water (forward flush) before a backflush was performed. The third system was an immersed UF-system (out-in) where negative pressure on the filtrate side is applied. The capillary UF-systems were operated at high flux and long backflush intervals when turbidity was low. At high turbidities the permeability declined and could only be restored by chemical cleaning. For this particular water the immersed system showed also a permeability decline, which was less pronounced. The permeability recovered in normal operation, when the turbidity declined. Using SEM and EDX the fouling could be mainly attributed to small particles (well below 3 μm). Qualitative element analysis showed that silica is the main component of the formed cake layer.
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Li, Gui Zhong, Ze Deng, Bo Wang e Meng Geng. "Dynamic Variation Character of CBM Reservoir Permeability during Depletion of High-Rank Coalbed Methane". Advanced Materials Research 233-235 (maggio 2011): 2267–71. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.2267.
Testo completoAbstract (sommario):
China is rich in CBM resources, but so far, some production wells present low production and rapid decline trend. In addition to these objective factors such as low permeability and complexity of geological structure of CBM reservoir, there is still the most important problem during the exploitation techniques that is the lack of understanding to dynamic variation character of CBM reservoir permeability, which leads to the unreasonable work of depletion for coalbed methane.Using P&M model and parameters from 3# coal seam of Shanxi Formation, Permian system in Qinshui basin, the permeability variations of this block (first decline, then ascend, reaching 2.8 times of initial permeability at the end) were analyzed, revealing good depletion prospect of this CBM field, and pointed that the higher Young's modulus is, the more obvious matrix shrinkage is and the higher gas saturation is, the more favor for permeability improvement through sensitivity analysis. Finally, two suggestions were proposed, (1) add the 'permeability variations' to the parameters for CBM block select, which may find the "innate" in the late development of the poor condition of properties easy to improve, develop potential for larger blocks. (2) Adjust and optimize the depletion method (amplitude and frequency of bleeding, pressure reduction) according to the permeability variation characters discussed in this paper
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Li, Shi Ji, Ze Hua Wang, Yu Xue Sun e Jian Bo Xie. "Stress Sensitivity of Low-Permeability Sandstone Reservoir". Advanced Materials Research 753-755 (agosto 2013): 686–89. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.686.
Testo completoAbstract (sommario):
In the time of low-permeability sandstone reservoir explored, effective stress rise gradually, stress sensitivity has happened, which cause permeability decline. Allowing to initial geostress, the study on Jilin oilfield Fuxin326 oil layer and made the rock core experiment are presented. The experimental results show that the stress sensitivity of this oil layer is small the regularity of permeability changes is in accordance with exponential function. The stress sensitivity of high permeability core is larger than low permeability. Moreover, experiments and theoretical analysis shows that low permeability core has a smaller permeability loss than high permeability core in load and unload process. Loading and unloading process leads to elastic plastic deformation of rocks, and it is the major reason which permeability can not return completely.
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Sun, Yu Xue, Fei Yao e Jing Yuan Zhao. "Research on Stress Sensitivity of Low Permeability Sand Stone Reservoir". Advanced Materials Research 317-319 (agosto 2011): 2432–35. http://dx.doi.org/10.4028/www.scientific.net/amr.317-319.2432.
Testo completoAbstract (sommario):
In the process of low-permeability sandstone reservoir exploitation, stress sensitivity takes place with the effective stress rises gradually, which will cause permeability decline. Allowing to the condition of in-situ stress, the study and experiment on the rock core in Jilin oil field Fuxin326 oil layer are presented. The experimental results show that the stress sensitivity of this oil layer is small; the regularity of permeability changes is in accordance with exponential function. The stress sensitivity of high permeability core is larger than that of low permeability core. Moreover, experimental and theoretical analysis shows that low permeability core has a larger permeability loss than high permeability core in loading and unloading process where elastic plastic deformation of rock will happen, which is the major reason that permeability loss can not return completely.
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Hamami, Happy Suryati, Abdul Qadir, Satriyas Ilyas e Bambang Budhianto. "SEED DETERIORATION PATTERN OF FOUR BAMBARA GROUNDNUT LANDRACES (Vigna subterraneasubterranean (L) Verdc) IN OPEN STORAGE SYSTEM". Informatika Pertanian 27, n. 2 (3 dicembre 2018): 111. http://dx.doi.org/10.21082/ip.v27n2.2018.p111-118.
Testo completoAbstract (sommario):
Bambara groundnut (Vigna subterranea (L.) Verdc) is a potential commodity to be developed in Indonesia, however, the production is done only once a year, therefore, it needs proper seed storage. The aim of this research was to study seed deterioration patterns of four bambara groundnut landraces stored in packages with different permeability in an open storage system for up to 6 months. This experiment was conducted from November 2015 to July 2016 at Seed Technology Laboratory, Department of Agronomy and Horticulture, IPB. Stages of experiment as follow: calculation of packaging permeability, seed storage, preparation and fitting data to regression equation.The packaging used in the study is aluminum foil, pp plastic and plastic sacks which have measured its permeability. The result showed that the seed deterioration of four bambara groundnut landraces in three packaging permeability has common sigmoidpattern with equation model: y = a / {1 + exp ((x + b) / c)}. The seed deterioration pattern based on SG and EC variables with the faster rate of decline occurred in Sumedang landrace packed in plastic sack (permeability = 1.4681 g/day m2 mm/Hg), thus having a shorter storability. The slower rate of decline occurred in Gresik landrace packed in aluminum foil (permeability = 0.098 g/day m2 mm/Hg), this means that it has a longer storability.
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Hamami, Happy Suryati, Abdul Qadir, Satriyas Ilyas e Bambang Budhianto. "SEED DETERIORATION PATTERN OF FOUR BAMBARA GROUNDNUT LANDRACES (Vigna subterraneasubterranean (L) Verdc) IN OPEN STORAGE SYSTEM". Informatika Pertanian 27, n. 2 (3 dicembre 2018): 111. http://dx.doi.org/10.21082/ip.v27n2.2018.p111-118.
Testo completoAbstract (sommario):
Bambara groundnut (Vigna subterranea (L.) Verdc) is a potential commodity to be developed in Indonesia, however, the production is done only once a year, therefore, it needs proper seed storage. The aim of this research was to study seed deterioration patterns of four bambara groundnut landraces stored in packages with different permeability in an open storage system for up to 6 months. This experiment was conducted from November 2015 to July 2016 at Seed Technology Laboratory, Department of Agronomy and Horticulture, IPB. Stages of experiment as follow: calculation of packaging permeability, seed storage, preparation and fitting data to regression equation.The packaging used in the study is aluminum foil, pp plastic and plastic sacks which have measured its permeability. The result showed that the seed deterioration of four bambara groundnut landraces in three packaging permeability has common sigmoidpattern with equation model: y = a / {1 + exp ((x + b) / c)}. The seed deterioration pattern based on SG and EC variables with the faster rate of decline occurred in Sumedang landrace packed in plastic sack (permeability = 1.4681 g/day m2 mm/Hg), thus having a shorter storability. The slower rate of decline occurred in Gresik landrace packed in aluminum foil (permeability = 0.098 g/day m2 mm/Hg), this means that it has a longer storability.
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Huang, Yu, Xiaoping Li e Xiaohua Tan. "Transient Pressure and Rate Decline Analysis for Horizontal Well in Stress-Sensitive Composite Reservoir". Mathematical Problems in Engineering 2018 (31 ottobre 2018): 1–11. http://dx.doi.org/10.1155/2018/8672578.
Testo completoAbstract (sommario):
The existence of stress sensitivity effect made the percolation mechanism of low-permeability reservoirs significantly complex. Further, numerous reservoirs have composite stratum properties in actual development procedure. This paper based on the concept of permeability stress sensitivity presents an unsteady flow model for horizontal well taking both stress sensitivity and composite reservoir into account. Analytic solutions for the transient pressure and the rate decline behaviors are obtained by comprehensive utilization of regular perturbation method, Laplace transformation, orthogonal transformation, and Stehfest numerical inversion. The example analysis verifies that the proposed model is reliable and practical. Likewise, there is a discussion of the influence of permeability modulus and other relevant parameters on the transient pressure and the rate decline for horizontal well in stress-sensitive composite reservoir. The work of this paper improved the previous researches and provided a more accurate basis for transient flow analysis and formation evaluation of this typical reservoir.
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Fénelon, Karine, Cédric R. H. Lamboley, Nicole Carrier e Paul C. Pape. "Calcium buffering properties of sarcoplasmic reticulum and calcium-induced Ca2+ release during the quasi-steady level of release in twitch fibers from frog skeletal muscle". Journal of General Physiology 140, n. 4 (24 settembre 2012): 403–19. http://dx.doi.org/10.1085/jgp.201110730.
Testo completoAbstract (sommario):
Experiments were performed to characterize the properties of the intrinsic Ca2+ buffers in the sarcoplasmic reticulum (SR) of cut fibers from frog twitch muscle. The concentrations of total and free calcium ions within the SR ([CaT]SR and [Ca2+]SR) were measured, respectively, with the EGTA/phenol red method and tetramethylmurexide (a low affinity Ca2+ indicator). Results indicate SR Ca2+ buffering was consistent with a single cooperative-binding component or a combination of a cooperative-binding component and a linear binding component accounting for 20% or less of the bound Ca2+. Under the assumption of a single cooperative-binding component, the most likely resting values of [Ca2+]SR and [CaT]SR are 0.67 and 17.1 mM, respectively, and the dissociation constant, Hill coefficient, and concentration of the Ca-binding sites are 0.78 mM, 3.0, and 44 mM, respectively. This information can be used to calculate a variable proportional to the Ca2+ permeability of the SR, namely d[CaT]SR/dt ÷ [Ca2+]SR (denoted release permeability), in experiments in which only [CaT]SR or [Ca2+]SR is measured. In response to a voltage-clamp step to −20 mV at 15°C, the release permeability reaches an early peak followed by a rapid decline to a quasi-steady level that lasts ∼50 ms, followed by a slower decline during which the release permeability decreases by at least threefold. During the quasi-steady level of release, the release amplitude is 3.3-fold greater than expected from voltage activation alone, a result consistent with the recruitment by Ca-induced Ca2+ release of 2.3 SR Ca2+ release channels neighboring each channel activated by its associated voltage sensor. Release permeability at −60 mV increases as [CaT]SR decreases from its resting physiological level to ∼0.1 of this level. This result argues against a release termination mechanism proposed in mammalian muscle fibers in which a luminal sensor of [Ca2+]SR inhibits release when [CaT]SR declines to a low level.
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Helmi, Mia Ferian, Muhammad Zakiy Y., Dinar Kaesti, Maulida Aulia Fadhina e Anisa Novia Risky. "Analysis of the Difference between Hydraulic Fracturing and Flow Channel Fracturing". Journal of Petroleum and Geothermal Technology 1, n. 1 (17 luglio 2020): 1. http://dx.doi.org/10.31315/jpgt.v1i1.3320.
Testo completoAbstract (sommario):
As time goes by, there will be a decline in formation productivity, as reflected in the decline in the rate of oil production from production wells. The decline in the rate of production was caused by many things such as a decrease in reservoir pressure, also formation damage. Where damage to the formation will result in a decrease in rock permeability. The decrease in rock permeability is caused by the blockage of rock pores due to the invasion of solids and drill mud filtrate, cementing, fluid fluids or previous stimulation. Besides the small rate of oil production can also be caused by the low natural permeability of rocks. With the decreasing productivity of the formation, it is necessary to make efforts to increase the productivity of the formation again, where one of them is by the method of hydraulic fracture stimulation. In this analysis, we will discuss the difference between conventional stimulation methods and flow channel fracturing. Flow channel fracturing is a fracturing process by making a network around proppant granules to form proppant pillar, so that a path is formed for the fluid to flow more easily. What distinguishes between conventional hydraulic fracturing with flow channel fracturing is the resulting fracture form, fracturing fluid injection pattern, and the amount of proppant used.
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Li, Pingyou, Mingqiang Hao, Jinghong Hu, Zhixing Ru e Zhiping Li. "A new production decline model for horizontal wells in low-permeability reservoirs". Journal of Petroleum Science and Engineering 171 (dicembre 2018): 340–52. http://dx.doi.org/10.1016/j.petrol.2018.07.059.
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Shen, Y., S. Wang e S. He. "Improving Decline-curve Analysis of Low-permeability Gas Wells Using Type Curves". Petroleum Science and Technology 31, n. 7 (aprile 2013): 738–47. http://dx.doi.org/10.1080/10916466.2010.533142.
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Wang, Qian, Piroska Lorinczi e Paul W. J. Glover. "Oil production and reservoir damage during miscible CO2 injection". Leading Edge 39, n. 1 (gennaio 2020): 22–28. http://dx.doi.org/10.1190/tle39010022.1.
Testo completoAbstract (sommario):
The blockage and alteration of wettability in reservoirs caused by asphaltene deposits are problems that contribute to poor oil recovery performance during carbon dioxide (CO2) injection. Oil production and reservoir damage are both controlled by macroscopic interlayer heterogeneity and microscopic pore-throat structure and may be optimized by the choice of flooding method. In this work, the residual oil distribution and the permeability decline caused by organic and inorganic precipitation after miscible CO2 flooding and water-alternating-CO2 (CO2-WAG) flooding have been studied by carrying out core-flooding experiments on a model heterogeneous three-layer reservoir. For CO2, flooding experimental results indicate that the low-permeability layers retain a large oil production potential even in the late stages of production, while the permeability decline due to formation damage is larger in the high-permeability layer. We found that CO2-WAG can reduce the influence of heterogeneity on the oil production, but it results in more serious reservoir damage, with permeability decline caused by CO2–brine–rock interactions becoming significant. In addition, miscible CO2 flooding has been carried out for rocks with similar permeabilities but different wettabilities and different pore-throat microstructures in order to study the effects of wettability and pore-throat microstructure on formation damage. Reservoir rocks with smaller pore-throat sizes and more heterogeneous pore-throat microstructures were found to be more sensitive to asphaltene precipitation, with corresponding lower oil recovery and greater decreases in permeability. However, it was found that the degree of water wetness for cores with larger, more connected pore-throat microstructures became weaker due to asphaltene precipitation to pore surfaces. Decreasing the degree of water wetness was found to be exacerbated by increases in the sweep volume of injected CO2 that arise from cores with larger and better connected pore throats. Erosion of water wetness is a disadvantage for enhanced oil recovery operations as asphaltene precipitation prevention and control measures become more necessary.
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Li, Kewen, e Roland N. Horne. "A Decline Curve Analysis Model Based on Fluid Flow Mechanisms". SPE Reservoir Evaluation & Engineering 8, n. 03 (1 giugno 2005): 197–204. http://dx.doi.org/10.2118/83470-pa.
Testo completoAbstract (sommario):
Summary Decline-curve-analysis models are used frequently but still have many limitations. Approaches of decline-curve analysis used for naturally fractured reservoirs developed by waterflooding have been few. To this end, a decline-analysis model derived on the basis of fluid-flow mechanisms was proposed and used to analyze the oil-production data from naturally fractured reservoirs developed by waterflooding. Relative permeability and capillary pressure were included in this model. The model reveals a linear relationship between the oil-production rate and the reciprocal of the oil recovery or the accumulated oil production. We applied the model to the oil-production data from different types of reservoirs and found a linear relationship between the production rate and the reciprocal of the oil recovery as foreseen by the model, especially at the late period of production. The values of maximum oil recovery for the example reservoirs were evaluated with the parameters determined from the linear relationship. An analytical oil-recovery model was also proposed. The results showed that the analytical model could match the oil-production data satisfactorily. We also demonstrated that the frequently used nonlinear type curves could be transformed to linear relationships in a log-log plot. This may facilitate the production-decline analysis. Finally, the analytical model was compared with conventional models. Introduction Estimating reserves and predicting production in reservoirs has been a challenge for many years. Many methods have been developed in the last several decades. One frequently used technique is the decline-curve-analysis approach. There have been a great number of papers on this subject. Most of the existing decline-curve-analysis techniques are based on the empirical Arps equations: exponential, hyperbolic, and harmonic. It is difficult to foresee which equation the reservoir will follow. On the other hand, each approach has some disadvantages. For example, the exponential decline curve tends to underestimate reserves and production rates; the harmonic decline curve has a tendency to overpredict the reservoir performance. In some cases, production-decline data do not follow any model but cross over the entire set of curves. Fetkovich combined the transient rate and the pseudosteady-state decline curves in a single graph. He also related the empirical equations of Arps to the single-phase-flow solutions and attempted to provide a theoretical basis for the Arps equations. This was realized by developing the connection between the material balance and the flow-rate equations on the basis of his previous papers. Many derivations were based on the assumption of single-phase oil flow in closed-boundary systems. These solutions were suitable only for undersaturated(single-phase) oil flow. However, many oil fields are developed by waterflooding. Therefore, two-phase fluid flow (rather than single-phase flow)occurs. In this case, Lefkovits and Matthews derived the exponential decline form for gravity-drainage reservoirs with a free surface by neglecting capillary pressure. Fetkovich et al. included gas/oil relative permeability effects on oil production for solution-gas drive through the pressure-ratio term. This assumes that the oil relative permeability is a function of pressure. It is known that gas/oil relative permeability is a function of fluid saturation, which depends on fluid/rock properties.
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Dull, Randal O., Bracken J. DeWitt, Ramani Dinavahi, Larry Schwartz, Christopher Hubert, Nathan Pace e Clara Fronticelli. "Quantitative assessment of hemoglobin-induced endothelial barrier dysfunction". Journal of Applied Physiology 97, n. 5 (novembre 2004): 1930–37. http://dx.doi.org/10.1152/japplphysiol.00102.2004.
Testo completoAbstract (sommario):
Hemoglobin (Hb)-based O2 carriers (HBOC) are undergoing extensive development as potential “blood substitutes.” A major problem associated with these molecules is an increase in microvascular permeability and peripheral vascular resistance. In this paper, we utilized bovine lung microvascular endothelial cell monolayers and simultaneously measured Hb-induced changes in transendothelial electrical resistance, diffusive albumin permeability, and diffusive Hb permeability ( PDH) for three forms of Hb: natural tetrameric human Hb-A and two polymerized recombinant HBOCs containing α-human and β-bovine chains designated Hb-Polytaur (molecular mass: 500 kDa) and Hb-(Polytaur)n (molecular mass: ∼1,000,000 Da), respectively. Hb-Polytaur and Hb-(Polytaur)n are being evaluated for clinical use as HBOCs. All three Hb molecules induce a rapid decline of transendothelial electrical resistance to 30% of baseline. Diffusive albumin permeabiltiy increases, on average, approximately ninefold (2.78 × 10−7 vs. 2.47 × 10−6 cm/s) in response to Hb exposure. All three Hb molecules induce an increase in their own permeability, a process that we have called Hb-induced Hb permeability. The magnitude of change of PDH is also related to Hb size. When PDH is corrected for the diffusive coefficient for each Hb species, no evidence of restricted diffusion is found. Immunofluorescent images demonstrate Hb-induced actin stress fiber formation and large intercellular gaps. These data provide the first quantitative assessment of the effect of polymerized HBOC on their own diffusion rates over time. We discuss the importance of these findings in terms of Hb extravasation rates, molecular sieving, and clinical consequences of HBOC use.
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Camacho Velazquez, Rodolfo, Mario A. Vasquez-Cruz, Rafael Castrejon-Aivar e Victor Arana-Ortiz. "Pressure Transient and Decline Curve Behaviors in Naturally Fractured Vuggy Carbonate Reservoirs". SPE Reservoir Evaluation & Engineering 8, n. 02 (1 aprile 2005): 95–112. http://dx.doi.org/10.2118/77689-pa.
Testo completoAbstract (sommario):
Summary This study presents a new way to model high secondary porosity, mainly vuggy porosity, in naturally fractured reservoirs. New solutions are presented for two cases, one in which there is no primary flow through the vugs (which is an extension of the Warren and Root model) and one in which the dissolution process of pore throats has created an interconnected system of vugs and caves. In both cases, there is an interaction between matrix, vug, and fracture systems. New insights are provided. Both pressure and production responses during transient and boundary-dominated flow periods are explored. In transient well tests, for the case in which there is no primary flow through the vugs, a change of slope could be present during the transition period. Thus, this study shows that slope ratios of 2:1 of an early- or late-time segment vs. a transition segment do not necessarily imply transient interaction between matrix and fractures. It is also shown that the presence of vugs and caves may have a definitive influence on decline-curve and cumulative production behaviors; therefore, it is necessary to incorporate vuggy porosity in the process of type-curve match. Finally, the use of the methodology obtained in this work is illustrated with synthetic and field examples. Introduction Most of the world's giant fields produce from naturally fractured and vuggy carbonate reservoirs that have complex pore systems, mainly because carbonate rocks are particularly sensitive to post-depositional diagenesis, including dissolution, dolomitization, and fracturing processes. Complete leaching of grains by meteoric pore fluids can lead to textural inversion, which may enhance reservoir quality through dissolution or occlude reservoir quality through cementation. Some works have classified carbonates on the basis of fabric-selective and nonfabric-selective pore types. The nonfabric-selective types are vugs and channels, caverns, and fractures. For the purpose of this work, no distinction is made on vugs, caverns, and channels, and they will be denoted by the term vugs. Thus, vugs may vary in size from millimeters to meters in diameter. Vugs are the result of carbonate and/or sulfate dissolution. From core observations, the matrix-porosity types adjacent to the vuggy zones are moldic, solution-enlarged microfractures and solution-enlarged intercrystalline. Thus, it is possible to have a permeability enhancement adjacent to the vuggy zones. Three porosity types (matrix, fractures, and vugs) are usually present in naturally fractured, vuggy carbonate reservoirs. The determination of permeability and porosity in vuggy zones from core measurements is likely to be pessimistic because of sampling problems. In areas lacking cores, openhole wireline logs may be used to help identify vuggy zones; however, vugs are not always recognized by conventional logs because of their limited vertical resolution. Vuggy porosity is common in many carbonate reservoirs, and its importance in the petrophysical and productive characteristics of a carbonate rock has been recognized by several works. Vugular porosity can be subdivided into connected and disconnected types. The effect of vugs on permeability is related to their connectivity. High permeability may be present in vuggy zones by solution enhancement of pore throats, which creates an interconnected system of vugs. The presence of high-porosity and high-permeability vuggy zones may diminish waterflood effectiveness and leave a large amount of bypassed oil in the lower-permeability matrix. One purpose of our work is to present a technique to identify high secondary porosity, mainly vuggy porosity. It has been observed in the literature that vugular zones strongly influence production performance. This reference addresses the problem of modeling vuggy naturally fractured reservoirs, allowing the possibility of primary flow through vugs, and develops a method to identify vuggy reservoirs on well tests and decline curves, evaluate porosity associated with vugs and fractures, and determine vuggy connectivity. The proposed model can be used in numerical simulators. Some comparisons between the results of analytical solutions derived in this work and those obtained with a numerical simulator, which uses the proposed model, are presented.
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Jin, Guan Xiu, e Cheng Yan Zhu. "Influence of Structure Parameters on Moisture Permeability of Fabric Woven by Fine PP Fiber with Star Section". Advanced Materials Research 502 (aprile 2012): 292–96. http://dx.doi.org/10.4028/www.scientific.net/amr.502.292.
Testo completoAbstract (sommario):
To study the influence of structure parameters on moisture permeability of fabric woven by fine pp fiber with star section, nine fabrics with different structure and tightness had been woven for experiment, and a moisture permeability test with moisture absorbtion method was performed and compared for these fabrics. Some conclusions are obtained: the moisture permeability showed direct correlation with fabric texture and tightness. It will be improved as the the float of weave get longer. Moreover it will decline with the increasing of fabric tightness and showed significant correlation with Polynomial function when the results fitted with it.
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Ogawa, S., S. Koga, K. Kuwabara, J. Brett, B. Morrow, S. A. Morris, J. P. Bilezikian, S. C. Silverstein e D. Stern. "Hypoxia-induced increased permeability of endothelial monolayers occurs through lowering of cellular cAMP levels". American Journal of Physiology-Cell Physiology 262, n. 3 (1 marzo 1992): C546—C554. http://dx.doi.org/10.1152/ajpcell.1992.262.3.c546.
Testo completoAbstract (sommario):
Prolonged exposure to hypoxia, as at high altitude, results in increased vascular permeability that may be ameliorated by administration of glucocorticoids. To understand mechanisms underlying these observations, cultured bovine aortic and pulmonary artery endothelial cells (ECs) were subjected to hypoxia, and changes in monolayer permeability and adenosine 3',5'-cyclic monophosphate (cAMP) levels were assessed. Exposure of both types of cultured ECs to hypoxia (PO2 approximately 14 Torr) led to a time- and dose-dependent increase in monolayer permeability, as measured by diffusion of radiolabeled solutes, which was associated with a progressive decrease in EC cAMP levels from 60 to 15 pmol/mg protein, and a decrease in EC adenylate cyclase activity. The change in endothelial barrier function was prevented by addition of cAMP analogues. Pertussis toxin protected EC monolayers from hypoxia-mediated increase in permeability while maintaining cAMP levels and adenylate cyclase activity. Addition of dexamethasone to EC monolayers before or simultaneously with their incubation under hypoxic conditions blocked the hypoxia-mediated increase in monolayer permeability. Dexamethasone pretreatment also prevented the decline in cAMP and adenylate cyclase levels in oxygen-deprived cultures. These data indicate that hypoxia decreases EC barrier function by lowering adenylate cyclase activity and cellular cAMP levels. They suggest that dexamethasone may exert its protective effect, in part, by preventing the hypoxia-induced decline in adenylate cyclase activity, leading to an increase in cellular cAMP and maintenance of EC barrier function.
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Dou, Hong'en, Changchun Chen, Yu Wen Chang, Yanjun Fang, Xinbin Chen e Wenxin Cai. "Analysis and Comparison of Decline Models: A Field Case Study for the Intercampo Oil Field, Venezuela". SPE Reservoir Evaluation & Engineering 12, n. 01 (26 febbraio 2009): 68–78. http://dx.doi.org/10.2118/106440-pa.
Testo completoAbstract (sommario):
Summary Intercampo oil field, which contains unconsolidated reservoirs driven by edge water and bottom water, is characterized by heavy oil with mid-high permeability and high oil saturation. The three classical models of the Arps model were applied in 13 horizontal and vertical wells in the oil field; also, the paper introduces two models that are not widely applied for decline analysis and forecasting in the wells. Decline features between vertical and horizontal wells were compared. The results accord well with the actual data from the oil field. The authors point out that these decline analysis models are applicable not only for vertical wells but also for horizontal wells. The authors would like to emphasize that four decline models discussed in the paper. In regard to screening and comparison of decline analysis models, this paper illustrates how to select and use a model, as well as the model's application conditions and their features. The screened models are recommended for production performance analysis of wells, reservoirs and oil fields. Introduction Existing decline curve analysis techniques, which include three Arps models (exponential, hyperbolic, and harmonic, 1945), and the Fetkovich model (1980), are derived empirically; the Arps models are still the preferred method for forecasting oil production and proven reserve. These methods have played a very important role in the exploration and development of oil fields worldwide (Arps 1945, Arps 1956, Fetkovich et al. 1980, Fetkovich et al. 1987, Fetkovich et al. 1996). Gentry and McCray (1978) presented a method to define decline curve. They claimed their equation might be superior to the Arps equations by defining certain decline curves. However, the model was derived from the hyperbolic model of the Arps model; their equation has a parameter qi of initial production rate computed by the Darcy Law. This means that the application of their method requires more parameters, such as relative permeability curve, radius of drainage, formation thickness, reservoir pressure at external drainage radius, and well bore terminal pressure. On this point, in their example the extrapolation with their model is not seen because the method is not a pure production-time relationship. Furthermore, use of this model to extrapolate future production is restricted by the data requirements. Li and Horne (2002, 2005) developed an analytical model, called the Li-Horne model, based on fluid flow mechanisms. The model was developed under the spontaneous water imbibition condition. Li and Horne also thought it difficult to predict which Arps equation a reservoir would follow. However, they made a conceptual error in their reasoning of the Arps models. In fact, we need to judge the decline type before using the Arps model to make production decline analysis. Li and Horne used only two special cases of decline exponent, n = 0 and 1, then compared the exponential model and harmonic model with any models. Hence, we think Li and Horne's comparison of several oil fields is not meaningful in cases where they did not get a concrete decline exponent n. When the Li-Horne model was applied to the actual oil fields, the values of a0 and b0 were regressed from the actual oilfield data, but not the calculation values from their equations. Because the models constants of the Arps and Li-Horne model regress from the actual oil fields, they include different reservoir type and fluid flow information (high permeability, low permeability, naturally fractured low permeability, complex, fault reservoir, etc.; single flow and multiphase flow, etc.). Therefore, the decline analysis models based on purely statistical models do not have any association with fluid flow mechanism, reservoir types, fluids characteristics, steady or unsteady flow, and single or multiphase flow. We are inclined to refer to this as an empirical rather than an analytical model. The other two decline analysis models introduced in this paper, the Orstrand-Weng model (Arps 1945, Weng 1992) and the T model, were both proposed for predicting oil field production in China during the 1980s. The main purpose of this paper is to compare application conditions and results among four models: Arps, Orstrand-Weng, T and the Li-Horne model.
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Qing, Tian, Peng Cheng Liu e Zong Yao Qi. "The Effect of Stress-Sensitivity on Gas well Production in Volcanic Gas Reservoirs". Advanced Materials Research 962-965 (giugno 2014): 636–41. http://dx.doi.org/10.4028/www.scientific.net/amr.962-965.636.
Testo completoAbstract (sommario):
During the volcanic gas reservoirs development, stress-sensitivity will result in permeability decline with formation pressure drop, lowering gas production and affecting the whole gas reservoirs development program. On the basis of the stress-sensitivity experiments on volcanic rocks, the characteristic of stress-sensitivity in volcanic reservoirs is analyzed. On this basis, this paper studies the prediction method of gas well productivity in volcanic gas reservoirs with stress-sensitivity, and establishes the mathematical model of constant pressure production in volcanic gas reservoirs. The results show that the permeability of volcanic rocks has an exponential relationship with effective stress. The stronger the stress-sensitivity is, the more the gas well productivity losses under the same conditions. And the reservoir stress-sensitivity will increase the degree of gas well unsteady production decline.
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Jiang, Shuai, Zheng Ming Yang, Xue Wei Liu, Meng Ting Wang e Qian Zhang. "Study on the Nonlinear Flow Percolation Law in Low Permeability Carbonate Reservoir of HF Oilfield". Applied Mechanics and Materials 644-650 (settembre 2014): 5065–70. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.5065.
Testo completoAbstract (sommario):
With the development of the global oil industry,the production of the normal or high permeability reservoirs decline rapidly. Therefore, more and more low permeability reservoirs are used to the production stimulation. The oilfields overseas make great contribution to CNPC. The HF oilfield is one oilfield that the CNPC have in overseas. The HF oilfield is mainly the low permeability carbonate reservoirs which make it not easy to economically exploit. Due to the reason that the low permeability carbonate reservoirs present small porosity and the fluid’s flow situation in the low permeability carbonate reservoirs, the flow doesn't obey the Darcy's law. Thus it is greatly necessary to study the non-Darcy percolation characteristics. In this paper, the HF ‘s low permeability is tested and the threshold pressure gradient test is finished ,according to the experiment results, the nonlinear percolation ‘s law ,which is suited to HF-oil field , is illustrated and the reservoir classification is achieved.
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Zhang, Shizhong, Gangwei Fan, Dongsheng Zhang, Wenping Li, Tao Luo, Shuaishuai Liang e Zhanglei Fan. "A Model of Stress-Damage-Permeability Relationship of Weakly Cemented Rocks under Triaxial Compressive Conditions". Materials 16, n. 1 (26 dicembre 2022): 210. http://dx.doi.org/10.3390/ma16010210.
Testo completoAbstract (sommario):
To unravel the permeability variation mechanism of weakly cemented rocks (WCR), the paper conducted triaxial permeability tests on weakly cemented sandstones (WCS) collected from the Jurassic formation in northwest China. The paper identified the correlation of WCS permeability versus porosity, cementation structure, and mineral composition, further developing a model to characterize the WCS stress–damage–permeability relationship. The research indicated that the WCS permeability was initially high due to the naturally high porosity, large pore diameter, and loose particle cementation, thus favoring a significant decline as pore convergence in the compaction stage. In the residual stage, kaolinite and montmorillonite minerals disintegrated into water and narrowed fractures, causing a slight permeability increase from the initial to the maximum and residual stages. The WCS matrix fracturing was phenomenologically accompanied by clay mineral disintegration. By assuming that the matrix can be compressed, jointed, and fractured, the paper defined a damage variable D and accordingly developed a stress–damage–permeability relationship model that incorporated matrix compression, jointing, and fracturing. The model can describe the WCS permeability regime regarding the high initial permeability and slight difference of the maximum and residual permeabilities versus the initial.
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Cheng, Chaojie, Johannes Herrmann, Bianca Wagner, Bernd Leiss, Jessica A. Stammeier, Erik Rybacki e Harald Milsch. "Long-Term Evolution of Fracture Permeability in Slate: An Experimental Study with Implications for Enhanced Geothermal Systems (EGS)". Geosciences 11, n. 11 (28 ottobre 2021): 443. http://dx.doi.org/10.3390/geosciences11110443.
Testo completoAbstract (sommario):
The long-term sustainability of fractures within rocks determines whether it is reasonable to utilize such formations as potential EGS reservoirs. Representative for reservoirs in Variscan metamorphic rocks, three long-term (one month each) fracture permeability experiments on saw-cut slate core samples from the Hahnenklee well (Harz Mountains, Germany) were performed. The purpose was to investigate fracture permeability evolution at temperatures up to 90 °C using both deionized water (DI) and a 0.5 M NaCl solution as the pore fluid. Flow with DI resulted in a fracture permeability decline that is more pronounced at 90 °C, but permeability slightly increased with the NaCl fluid. Microstructural observations and analyses of the effluent composition suggest that fracture permeability evolution is governed by an interplay of free-face dissolution and pressure solution. It is concluded that newly introduced fractures may be subject to a certain permeability reduction due to pressure solution that is unlikely to be mitigated. However, long-term fracture permeability may be sustainable or even increase by free-face dissolution when the injection fluid possesses a certain (NaCl) salinity.
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Chen, Ye Fei, Zi Fei Fan, Jun Ni, Yun Juan Li e Qing Ying Hou. "The Development Technology Policy of Secondary Oil Recovery in the Overpressure Carbonate Reservoir". Advanced Materials Research 680 (aprile 2013): 295–300. http://dx.doi.org/10.4028/www.scientific.net/amr.680.295.
Testo completoAbstract (sommario):
Kenkiyak oilfield in kazakstan is a low porosity, extremely low permeability and overpressure carbonate reservoir. There are different reservoir and fracture characteristics in different region. The formation pressure decline seriously and water cannot be injected into the low permeability zone. Referring to the domestic and oversea research achievement, integrating regional geologic characteristics, numerical simulation results and reservoir engineering research results, we optimize a series of the development technology policy, including the reasonable gas and water injection modes and injection opportunity, the suitable well patterns and well spacing. Meanwhile, the development mode of energy supplement in the extremely low permeability and overpressure reservoir is explored.
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Rundek, Tatjana, Sabita Roy, Mady Hornig, Ying Kuen Cheung, Hannah Gardener, Janet DeRosa, Bonnie Levin et al. "Gut permeability and cognitive decline: A pilot investigation in the Northern Manhattan Study". Brain, Behavior, & Immunity - Health 12 (marzo 2021): 100214. http://dx.doi.org/10.1016/j.bbih.2021.100214.
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Jafari Dastgerdi, Ehsan, Mohammad Fazaelizadeh, Davood Zivar, Afshin Davarpanah e Ali Shabani. "Permeability Decline in Fractured Porous Media During Mineral Scaling: A Detailed Modeling Study". Natural Resources Research 31, n. 1 (16 gennaio 2022): 601–17. http://dx.doi.org/10.1007/s11053-021-09992-5.
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Santisukkasaem, Umarat, Fehintola Olawuyi, Peter Oye e Diganta B. Das. "Artificial Neural Network (ANN) For Evaluating Permeability Decline in Permeable Reactive Barrier (PRB)". Environmental Processes 2, n. 2 (18 aprile 2015): 291–307. http://dx.doi.org/10.1007/s40710-015-0076-4.
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Zhang, Xiaoyang, Caifang Wu, Ziwei Wang e Dongjing Xu. "Postfracturing permeability prediction for CBM well with the analysis of fracturing pressure decline". Energy Science & Engineering 7, n. 6 (7 ottobre 2019): 3111–23. http://dx.doi.org/10.1002/ese3.483.
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Wu, Mingtao, Xiaodong Wang, Wenqi Zhao, Lun Zhao, Meng Sun e Hai Zhou. "Rate Decline Analysis for Limited-Entry Well in Abnormally High-Pressured Composite Naturally Fractured Gas Reservoirs". Applied Sciences 9, n. 9 (1 maggio 2019): 1821. http://dx.doi.org/10.3390/app9091821.
Testo completoAbstract (sommario):
Most naturally fractured gas reservoirs in China exhibit strongly heterogeneous, abnormally high-pressured and, stress-sensitive behaviors. In this work, a semianalytical solution is developed to study the production performance for limited-entry well in composite naturally fractured formations. The pressure-dependent porosity and permeability, anisotropy and limited-entry characteristics are taken into consideration. Furthermore, conventional Warren-Root model is amended to accommodate for permeability anisotropy. Laplace and finite Fourier cosine transforms are used to solve the diffusivity equations. The model is verified on the basis of previous literature’s results and data of a field example from Moxi gas field in Southwest China. Through the parameters sensitivity analysis, the effects of prevailing factors on production performance are investigated. Results indicate that a large inner region radius and high mobility ratio can improve gas production rate in the early stage, while they also lead to a drastic decline of production rate in the late stage. Large permeability stress-dependent coefficient and low penetrated interval both have a negative impact on production rate. With its high efficiency and simplicity, this proposed approach can serve as a convenient tool to evaluate the behavior of partially penetrated production well in abnormally high-pressured composite naturally fractured gas reservoirs.
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Andrés, Sandro, David Santillán, Juan Carlos Mosquera e Luis Cueto-Felgueroso. "Hydraulic Stimulation of Geothermal Reservoirs: Numerical Simulation of Induced Seismicity and Thermal Decline". Water 14, n. 22 (16 novembre 2022): 3697. http://dx.doi.org/10.3390/w14223697.
Testo completoAbstract (sommario):
Enhanced Geothermal Systems (EGS) can boost sustainable development by providing a green energy supply, although they usually require the hydraulic stimulation of the reservoir to increase fluid flow and energy efficiency due to the low rock permeability at the required depths. The injection of fluids for hydraulic stimulation implies several risks, for instance, induced seismicity. In this work, we perform numerical simulations to evaluate the seismic risk in terms of fault reactivation, earthquake magnitude, and rupture propagation. The computational model includes the fully coupled thermo-hydro-mechanical equations and simulates faults as frictional contacts governed by rate-and-state friction laws. We apply our methodology to the Basel EGS project as a continuation of our previous work, employing the same parameters and conditions. Our results demonstrate that permeability stimulation is not only related to induced seismicity but also can induce a thermal decline of the reservoir over the years and during the energy production. The proposed methodology can be a useful tool to simulate induced earthquakes and the long-term operation of EGS.
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Wu, Dan, Binshan Ju, Shiqiang Wu, Eric Thompson Brantson, Yingkun Fu e Zhao Lei. "Investigation of productivity decline in inter-salt argillaceous dolomite reservoir due to formation damage and threshold pressure gradient: Laboratory, mathematical modeling and application". Energy Exploration & Exploitation 35, n. 1 (22 dicembre 2016): 33–53. http://dx.doi.org/10.1177/0144598716684308.
Testo completoAbstract (sommario):
The inter-salt argillaceous dolomite reservoirs in the central region of China contain large abundance of oil resources with ultra-low permeability and porosity. However, the oil wells in this area show a very quick reduction with the decline of formation pressure. This article aims to investigate the main possible reasons that affect oil well productivity in the target oilfield. This study begins with analysis of capillary microscopic model, core stress sensitivity experiments, and non-Darcy percolation experiments. The impact of effective stress on permeability and porosity of the reservoir was revealed in this article. The novel productivity model and productivity evaluation model which couples stress sensitivity and threshold pressure gradient were proposed. The analysis of capillary microscopic model shows stress sensitivity of permeability to be much greater than that of porosity during the process of depressurization. The core stress sensitivity experiments results indicate that permeability and effective stress show index relationship while porosity and effective stress show binomial relationship. Damage rate and recovery rate of permeability and porosity were put forward to describe the degree of influence of stress sensitivity on permeability and porosity. The models were used to investigate the factors that affect single well productivity for the target oilfield. Application of the proposed model to this tight oilfield indicates that, the degree of influence of stress sensitivity is much greater than that of threshold pressure gradient. In addition, the greater the stress sensitivity coefficient and threshold pressure gradient are, the greater the productivity reduction will be.
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Dickman, Kathleen G., Scott J. Hempson, Joseph Anderson, Scott Lippe, Liming Zhao, Robert Burakoff e Robert D. Shaw. "Rotavirus alters paracellular permeability and energy metabolism in Caco-2 cells". American Journal of Physiology-Gastrointestinal and Liver Physiology 279, n. 4 (1 ottobre 2000): G757—G766. http://dx.doi.org/10.1152/ajpgi.2000.279.4.g757.
Testo completoAbstract (sommario):
Rotaviruses infect epithelial cells of the small intestine, but the pathophysiology of the resulting severe diarrhea is incompletely understood. Histological damage to intestinal epithelium is not a consistent feature, and in vitro studies showed that intestinal cells did not undergo rapid death and lysis during viral replication. We show that rotavirus infection of Caco-2 cells caused disruption of tight junctions and loss of transepithelial resistance (TER) in the absence of cell death. TER declined from 300 to 22 Ω · cm2between 8 and 24 h after infection and was accompanied by increased transepithelial permeability to macromolecules of 478 and 4,000 Da. Distribution of tight junction proteins claudin-1, occludin, and ZO-1 was significantly altered during infection. Claudin-1 redistribution was notably apparent at the onset of the decline in TER. Infection was associated with increased production of lactate, decreased mitochondrial oxygen consumption, and reduced cellular ATP (60% of control at 24 h after infection), conditions known to reduce the integrity of epithelial tight junctions. In conclusion, these data show that rotavirus infection of Caco-2 intestinal cells altered tight junction structure and function, which may be a response to metabolic dysfunction.
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Guo, Wei, Rongze Yu, Xiaowei Zhang e Zhiming Hu. "Physical and mathematical modeling of gas production in shale matrix". Oil & Gas Sciences and Technology – Revue d’IFP Energies nouvelles 73 (2018): 12. http://dx.doi.org/10.2516/ogst/2018010.
Testo completoAbstract (sommario):
Shale gas mainly stores in shale matrix, and gas production in shale matrix is very important during exploration. In order to clarify gas production and transport mechanism in shale matrix, an experimental modeling of gas production in shale matrix was designed and conducted with Longmaxi shale samples collected from South of Sichuan. The experimental results show that gas production decline curve displays a “L” pattern which indicates initial production is high and declines rapidly, while late production is low and declines moderately; meanwhile, pressure propagation in shale matrix is quite slow due to ultralow permeability. Based on the results, a mathematical model was derived to describe gas production in shale matrix. The comparison between numerical solution of mathematical model and experimental results shows that the mathematical model can well describe gas transport in shale matrix. In addition, factors affecting gas production were investigated on the basis of the mathematical model. Adsorbed gas can replenish gas pressure in pores by desorption and delay pressure propagation, and gas production decreases very quickly when there is no adsorbed gas. Other parameters (diffusion coefficient, permeability and porosity) also need to be considered in shale gas development.
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Liu, Yan, e Langtao Zhu. "Integration of Multi-Region Material Balance Equation with Binomial Productivity Equation for Performance Prediction". Geofluids 2022 (30 marzo 2022): 1–10. http://dx.doi.org/10.1155/2022/5169602.
Testo completoAbstract (sommario):
In order to overcome the limitations of conventional material balance methods, a new multi-region material balance method, considering the strong heterogeneity and low-velocity non-Darcy flow characteristics of bio-reef gas reservoir, is proposed to estimate the development performance of reef reservoirs. Firstly, the reef reservoir is divided into two regions, the reef cover high-permeability development area and the reef edge low-permeability supplying area. Then, based on one-dimensional non-linear seepage mechanism and mass conservation principle, the multi-region supplying material balance equation is established. Finally, combined with the binomial productivity equation, the development performance can be easily estimated at different P / Z curves. The application results indicate that the low-permeability replenishment area plays an important role, especially after entering the decline stage, on the development performance of high-permeability region. Compared with the traditional material balance method, the new method can help for better understanding of unbalanced development in different regions and the replenishment effect of low-permeability region.
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Wilson, Margaret-Mary G., e John E. Morley. "Invited Review: Aging and energy balance". Journal of Applied Physiology 95, n. 4 (ottobre 2003): 1728–36. http://dx.doi.org/10.1152/japplphysiol.00313.2003.
Testo completoAbstract (sommario):
Humans over 70 yr of age often lose weight. This appears to be due to a physiological anorexia of aging as well as a loss of lean mass (sarcopenia) and, to a lesser extent, fat mass. The causes of the physiological anorexia of aging include changes in taste and smell and a decrease in adaptive relaxation of the fundus of the stomach, which leads to more rapid antral filling and early satiation. In addition, basal and stimulated levels of the satiating hormone, cholecystokinin, are increased. In men, the decline in testosterone leads to an increase in leptin and a loss of lean mass. Although resting metabolic rate declines with aging, this is mainly due to the decline in lean body mass. Energy metabolism is also decreased due to a decline in Na+-K+-ATPase activity, decreased muscle protein turnover, and possibly changes in mitochondrial membrane protein permeability. Physical energy expenditure declines with aging. Meal-induced thermogenesis shows a delay to peak, possibly due to a delay in gastric emptying. Inadequate data are available on the effect of aging in humans on other energy-producing mechanisms such as adaptive thermogenesis. These physiological changes place older men and women at major risk of developing pathological weight loss when they develop disease states, especially those associated with cytokine elaboration.