Duane H. Smith

Natural gas production from hydrate decomposition by depressurization

This paper presents a parametric study of natural gas production from the decomposition of methane hydrate in a confined reservoir by a depressurizing well. The one-dimensional linearized model suggested by Makogon is used in the analysis. For different well pressures and reservoir temperatures, distributions of temperature and pressure in the porous layer of methane hydrate and in the gas region are evaluated. The distance of the decomposition front from the well and the natural gas output as functions of time are also computed. Time evolutions of the resulting temperature and pressure profiles in the hydrate reservoir under various conditions are presented. Effects of variations in reservoir porosity and zone permeability are also studied. It is shown that the gas production rate is a sensitive function of well pressure, reservoir temperature and zone permeability.

Synthesis of methane gas hydrate in porous sediments and its dissociation by depressurizing

Abstract The clathrate compounds of methane gas hydrate (MGH) was synthesized in laboratory at a temperature of 273.5 K and at a pressure of 6.8–13.6 MPa, consisting of solid phase MGH dispersed within various custom-designed porous sediments. This synthesized MGH looks almost like the MGH made by Mother Nature in the strata in the natural gas hydrate (NGH) field. Using this synthesized MGH, the dissociation rate was measured by depressurizing method. From experimental results, the kinetic dissociation rate equation and order of the reaction were derived. It was found through experiments that the dissociation rate could be adjusted by the control of sediment properties. With respect to MGH formation reaction, the reaction rate equation and its reaction order were also derived.

Constant rate natural gas production from a well in a hydrate reservoir

Using a computational model, production of natural gas at a constant rate from a well that is drilled into a confined methane hydrate reservoir is studied. It is assumed that the pores in the reservoir are partially saturated with hydrate. A linearized model for an axisymmetric condition with a fixed well output is used in the analysis. For different reservoir temperatures and various well outputs, time evolutions of temperature and pressure profiles, as well as the gas flow rate in the hydrate zone and the gas region, are evaluated. The distance of the decomposition front from the well as a function of time is also computed. It is shown that to maintain a constant natural gas production rate, the well pressure must be decreased with time. A constant low production rate can be sustained for a long duration of time, but a high production rate demands unrealistically low pressure at the well after a relatively short production time. The simulation results show that the process of natural gas production in a hydrate reservoir is a sensitive function of reservoir temperature and hydrate zone permeability.

Particle transport and deposition in a hot-gas cleanup pilot plant

ABSTRACT Development of hot-gas filtration systems for advanced clean coal technologies has attracted considerable attention in recent years. The Integrated Gasification and Cleanup Facility (IGCF), which is an experimental pilot plant for testing performance of ceramic candle filters for hot-gas cleaning, has been operational at the Federal Energy Technology Center (FETC) in Morgantown, West Virginia, for several years. The present work describes a computer simulation study of gas flow and particle transport and deposition in the IGCF filter vessel with four filters. The stress transport model of FLUENT™ code is used for evaluating the gas mean velocity and the root mean-square fluctuation velocity fields in the IGCF filter vessel. The instantaneous fluctuation velocity vector field is simulated by a filtered Gaussian white-noise model. Ensembles of particle trajectories are evaluated using the recently developed PARTICLE code. The model equations of the code include the effects of lift and Brownian moti...

PORE-LEVEL MODELING OF IMMISCIBLE DRAINAGE: VALIDATION IN THE INVASION PERCOLATION AND DLA LIMITS

Motivated by a wide-range of applications from ground water remediation to carbon dioxide sequestration and by difficulties in reconciling experiments with previous modeling, we have developed a pore-level model of two-phase flow in porous media. We have attempted to make our model as physical and as reliable as possible, incorporating both capillary effects and viscous effects. After a detailed discussion of the model, we validate it in the very different limits of zero capillary number and zero-viscosity ratio. Invasion percolation (IP) models the flow in the limit of zero capillary number; results from our model show detailed agreement with results from IP, for small capillary numbers. Diffusion limited aggregation (DLA) models the flow in the limit of zero-viscosity ratio; flow patterns from our model have the same fractal dimension as patterns from DLA for small viscosity ratios.

Patchy cleaning of rigid gas filters - Transient regeneration phenomena : comparison of modelling to experiment

Abstract Rigid ceramic filter media, widely used for the removal of particles from gas streams at elevated temperatures tend to show patchy cleaning when the filter regeneration is incomplete [Filtr. Sep. (1989) 187]. In order to investigate the regeneration behaviour and the operational performance of partially regenerated, rigid gas cleaning filter media over many filtration cycles, experiments were performed in a filter test rig. The regeneration behaviour of the filter sample was characterized by the overall regeneration efficiency, the local frequency of regeneration, and the number and size of regenerated filter areas. Using only four adjustable parameters, our modelling results compare favourably with our experimental results, at room temperature. This favourable comparison of the regeneration behaviour between modelling and experiment is achieved only if it is assumed that cohesive and adhesive bonds, which are broken during filter regeneration, do not heal during the next filtration cycle. Assuming otherwise would cause (i) the dust cake to be removed at the same positions during every regeneration and (ii) the patch size to increase from cycle to cycle instead of decreasing as seen in the experiment. Therefore, the model development was guided by our extensive experimental results. This agreement of modelling with experiment indicates that the modelling has real predictive capabilities for operational filter cleaning. Both filter conditioning and dust cake compression significantly influence the operational performance of partially regenerated filter media.

Computational modeling of flow and sediment transport and deposition in meandering rivers

Abstract A computational modeling analysis of the flow and sediment transport, and deposition in meandering-river models was performed. The Reynolds stress transport model of the FLUENTTM code was used for evaluating the river flow characteristics, including the mean velocity field and the Reynolds stress components. The simulation results were compared with the available experimental data of the river model and discussed. The Lagrangian tracking of individual particles was performed, and the transport and deposition of particles of various sizes in the meandering river were analyzed. Particular attention was given to the sedimentation patterns of different size particles in the river-bend model. The flow patterns in a physical river were also studied. A Froude number based scale ratio of 1:100 was used, and the flow patterns in the physical and river models are compared. The result shows that the mean-flow quantities exhibit dynamic similarity, but the turbulence parameters of the physical river are different from the model. More strikingly, the particle sedimentation features in the physical and river models do not obey the expected similarity scaling.

Infrared spectra of Mg2Ca(SO4)3, MgSO4, hexagonal CaSO4, and orthorhombic CaSO4

Abstract Fourier-transform infrared (IR) spectra have been obtained from 450 to 1400 cm−1 for the sulfate ion in Mg2Ca(SO4)3, MgSO4, and the hexagonal and orthorhombic crystalline forms of CaSO4. This appears to be the first report of IR spectra for Mg2Ca(SO4)3 and hexagonal CaSO4. Except for the number of satellite peaks, the spectra of Mg2Ca(SO4)3 and hexagonal CaSO4 closely resemble those of MgSO4 and orthorhombic CaSO4. All of these spectra can be interpreted on the basis of C2v symmetry for the anion. The cause(s) of satellite peaks are uncertain; the satellites suggest that the sulfate may occupy more than one position or orientation, with major:minor occupancy ratios of about 3:2.

Analysis of Operational Filtration Data Part III: Re-entrainment and Incomplete Cleaning of Dust Cake

ABSTRACT Operational data for the hot-gas filtration system of the Integrated Gasification and Cleanup Facility (IGCF) at the Federal Energy Technology Center are carefully analyzed. A model that includes re-entrainment of filter-cake fragments following cleaning of the candle filters, as well as incomplete removal of cake from the filters by the cleaning backpulses of compressed air, is developed and used to interpret the data. The parameters of the model are evaluated with a least-square error fit procedure. It is shown that inclusion of the re-entrainment model significantly improves the fit to the data during the short interval (∼50 s after each backpulse) during which re-entrainment is predicted to occur by particle-transport modeling. The re-entrainment/incomplete-cleaning model is used to evaluate the buildup of filter-cake thickness and the filter-cake permeability. Both effects were significant for the data analyzed.

Analysis of operational filtration data part I. Ideal candle filter behavior

Operating data for the hot-gas filtration system of the Integrated Gasification and Cleanup Facility (IGCF) at the Federal Energy Technology Center are carefully analyzed. A model for candle filters is developed and used to describe the ideal filtration process. The parameters of the model are evaluated with a least-square error fit procedure. It is shown that the model predicts the time variation of the pressure drop with reasonable accuracy. The model is used to evaluate the buildup of filter-cake thickness and the filter-cake permeability.