The Event Horizon Telescope (EHT), now with its first ever image of the photon ring around the supermassive blackhole of M87, provides a unique opportunity to probe the physics of supermassive black holes through Very Long Baseline Interferometry (VLBI), such as the existence of the event horizon, the accretion processes as well as jet formation in Low Luminosity AGN (LLAGN). We build a theoretical model which includes an Advection Dominated Accretion Flow (ADAF) with emission from thermal and non-thermal electrons in the flow and a simple radio jet outflow. The predicted spectral energy distribution (SED) of this model is compared to sub-arcsec resolution observations to get the best estimates of the model parameters. The model-predicted radial emission profiles at different frequency bands are used to predict whether the inflow can be resolved by the EHT or with telescopes such as the Global 3-mm VLBI array (GMVA). In this work the model is initially tested with high resolution SED data of M87 and then applied to our sample of 5 galaxies (Cen A, M84, NGC 4594, NGC 3998 and NGC 4278). The model then allows us to predict if one can resolve the inflow for any of these galaxies using the EHT or GMVA.
The paper examines the sensitivity of reservoir simulations to uncertainties in viscosity. The simulations are performed for three different oils, ranging from light to viscous, for three different geological terrains. In each case, the viscosity has been estimated by a number of currently recommended prediction methods and by recourse to the measured values. The preliminary results indicate that the results of reservoir simulations are sensitive to the fluid viscosity. The sensitivity increases with increase in the absolute viscosity of the oil, increase in heterogeneity of the reservoir and increase in uncertainty in viscosity. The results show, that in the worst case scenario examined (e.g. heavy, viscous oils, ? > 6 cp) a ±1% error in viscosity will produce a 1% error in the cumulative production. Overall, the preliminary results indicate that the common assumption in reservoir simulations, that the accuracy of fluid properties has a marginal influence on the reservoir performance, is false. Uncertainties in viscosity can lead to large errors in predicted production rates, thus unduly influencing the economics of reservoir exploitation. Introduction For effective and efficient exploitation of oil fields, good reservoir characterisation is paramount; thus requiring an adequate understanding of rock and fluid properties. It has been petroleum industry practice to assume that fluid properties are well characterized and that all the uncertainty associated with numerical reservoir simulation is only related to uncertainty in the spatial distribution of rock properties. The present paper examines this preconception by analyzing the sensitivity of reservoir simulations to uncertainties in viscosity. Traditionally, viscosity values required in compositional simulators are either obtained by measuring lab-samples or by one of the available prediction methods. In principle, an accurate measurement of the fluid viscosity, to better than ±1%, can be obtained in a well-characterized experimental apparatus (e.g. primary instruments), with a well-defined uncertainty level, which cannot be demonstrated to be inconsistent with other data or with theory1. Although such instruments do exist 1 their use requires knowledge of a full, fluid mechanics, working equation and requires a number of corrections to be applied to the experimental data, making the analysis expensive and time-consuming and thus, these instruments are not suitable for routine analysis. The instruments currently used in the oil industry do not fulfill any of the requirements of a primary instrument, neither in the design nor in the operation, and consequently their accuracy is much lower. A comparative experimental study2, by five different laboratories, of an identical oil sample showed a spread in viscosity data of the order of ±20%. There is no reason to expect that the accuracy of the routine viscosity measurements, carried out in a standard petroleum sample characterisation, would normally be better than the results of this case.
The Event Horizon Telescope (EHT) provides a unique opportunity to probe the physics of supermassive black holes through Very Large Baseline Interferometry (VLBI), such as the existence of the event horizon, the accretion processes as well as jet formation in Low Luminosity AGN (LLAGN). We build a theoretical model which includes an Advection Dominated Accretion Flow (ADAF) and a simple radio jet outflow. The predicted spectral energy distribution (SED) of this model can be compared to observations to get the best estimates of the model parameters. The model-predicted radial emission profiles at different frequency bands can be used to predict whether the inflow can be resolved by the EHT or other telescopes. We have applied this method to some nearby LLAGN such as M84, NGC 4594, NGC 4278 and NGC 3998. We also estimate the model parameters for each of them using high resolution data from different surveys.
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