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81.
Computer modeling and simulation of coalbed methane resources 总被引：3，自引：0，他引：3
Coal seam gas reservoirs are complex both geologically and in the mechanism of gas production. Understanding these naturally fractured reservoirs for two-phase (gas–water) flow conditions is often limited by a lack of data. This paper illustrates that reservoir simulation is a powerful tool which can be used to determine key data requirements, and how variability in reservoir properties and operating practices affect performance at the field level. The paper presents examples of how reservoir simulation can be used to assess the efficiency of well completions (fracturing or cavitation), identify candidate wells for remedial treatment, examine methane drainage in advance of mining, and assess the impact of errors in measured data on long-term gas production forecasts. 相似文献
82.
A. J. Young R. R. Ross & A. C. Fabian 《Monthly notices of the Royal Astronomical Society》1998,300(1):L11-L15
We propose a model for the source of the X-ray background (XRB) in which low-luminosity active nuclei ( L ∼ 1043 erg s−1 ) are obscured ( N ∼ 1023 cm−2 ) by nuclear starbursts within the inner ∼ 100 pc. The obscuring material covers most of the sky as seen from the central source, rather than being distributed in a toroidal structure, and hardens the averaged X-ray spectrum by photoelectric absorption. The gas is turbulent with velocity dispersion ∼ few × 100 km s−1 and cloud–cloud collisions lead to copious star formation. Although supernovae tend to produce outflows, most of the gas is trapped in the gravity field of the star-forming cluster itself and the central black hole. A hot ( T ∼ 106 − 107 K) virialized phase of this gas, comprising a few per cent of the total obscuring material, feeds the central engine of ∼ 107 M⊙ through Bondi accretion, at a sub-Eddington rate appropriate for the luminosity of these objects. If starburst-obscured objects give rise to the residual XRB, then only 10 per cent of the accretion in active galaxies occurs close to the Eddington limit in unabsorbed objects. 相似文献
83.
Imad A.M. Ahmed Neil M.J. Crout Scott D. Young 《Geochimica et cosmochimica acta》2008,72(6):1498-1512
Time-dependent sorption and desorption of Cd on calcite was studied over 210 days utilizing 109Cd as a tracer to distinguish between ‘labile’ and ‘non-labile’ forms of sorbed Cd. Stabilizing the calcite suspensions for 12 months under atmospheric PCO2 and controlled temperature was necessary to reliably follow Cd dynamics following initial sorption. Results revealed time-dependant Cd sorption and marked desorption hysteresis by calcite under environmentally relevant conditions. Data obtained were fitted to a first-order kinetic model and a concentric shell diffusion model. Both models described the progressive transfer of Cd2+ to a less reactive form within calcite and subsequent desorption of Cd subject to different initial contact times. The kinetic model provided a better fit to the combined sorption and desorption data (R2 = 0.992). It differentiates between two ‘pools’ of sorbed Cd2+ on calcite, ‘labile’ and ‘non-labile’, in which labile sorbed Cd is in immediate equilibrium with the free Cd2+ ion activity in solution whereas non-labile Cd is kinetically restricted. For the diffusion model (R2 = 0.959), the rate constants describing Cd dynamics in calcite produced a half-life for Cd desorption of ∼175 d, for release to a ‘zero-sink’ solution. Results from this study allow comment on the likely mechanisms occurring at the calcite surface following long-term Cd sorption. 相似文献
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