33 research outputs found
Transition layer thickness at a fluid-porous interface
The length scale of the transition region between a porous layer and its overlying fluid layer is experimentally studied. The experimental setup consists of a rectangular channel, in which a fluid layer flows over a porous bed. Using particle image velocimetry and refractive index matching, two-dimensional velocity measurements in the interfacial region were performed. The thickness of this transition layer, defined by the height below the permeable interface up to which the velocity decreases to the Darcy scale, is measured and compared with the permeability and the matrix grain size. It was observed that the thickness of the transition zone, δ, is of the order of the grain diameter, and hence, much larger than the square root of the permeability as predicted by previous theoretical studies. The Reynolds number and the fluid height over the porous substrate were found to affect the gradient of the horizontal velocity component at the interfacial region while the length scale of the transition layer remains approximately unchanged. The effect of the porous matrix type has been investigated by utilizing spherical glass beads as well as granulates. Scaling the measured velocities by the interfacial velocity near the uppermost solid matrix resulted in a unique velocity distribution in the case of monodisperse glass beads, hinting that the interfacial velocity represents a proper scaling factor. However, for polydisperse granulate material deviation from this behavior was observed
Modeling of Two-Phase Flow with Deposition in Vertical Pipes
Deposition is found in many engineering processes,
such as the asphaltene deposition in oil pipelines/wellbores, and biological and chemical foulings in pipes or heat exchangers. These
deposition processes usually occur in a two-phase flow environment. This study develops a model for two-phase flow with deposition in vertical pipes. The model consists of three modules: Fluid Transport, Particle Transport, and Particle Deposition. The Fluid Transport module predicts the fluids’ velocities and pressure. The Particle
Transport module calculates the particle distribution. The Particle Deposition module models the actual attachment of particles onto the
wall. The model is verified against a few limiting cases with analytical solutions. Then, it is validated against experimental data for two-phase flow without deposition. Demonstration of the model for bubbly flow with deposition is performe
Integrated One-Dimensional Modeling of Asphaltene Deposition in Wellbores/Pipelines
—Asphaltene deposition in wellbores/pipelines causes serious production losses in the oil and gas industry. This work presents a numerical model to predict asphaltene deposition in
wellbores/pipelines. This model consists of two modules: a Thermodynamic Module and a Transport Module. The Thermodynamic Module models asphaltene precipitation using the Peng-Robinson Equation of State with Peneloux volume translation (PR-Peneloux EOS). The Transport Module covers the modeling of fluid transport, asphaltene particle transport and asphaltene deposition. These
modules are combined via a thermodynamic properties lookup-table generated by the Thermodynamic Module prior to simulation. In this
work, the Transport Module and the Thermodynamic Module are first verified and validated separately. Then, the integrated model is
applied to an oilfield case with asphaltene deposition problem where a reasonably accurate prediction of asphaltene deposit profile is
achieve
Three Dimensional Measurements of Asphaltene Deposition in a Transparent Micro-Channel
This study describes a novel experimental approach to directly measure the thicknesses of asphaltene deposits in micro-channels. The thickness of the asphaltene deposit is estimated using a visualization technique based on 3D digital microscopy. The working fluid is a mixture of n-heptane and dead oil. Induced by the addition of n-heptane, the asphaltenes present in crude oil phase separate at ambient temperature to form aggregates of asphaltene-rich phase. Part of the asphaltene aggregates deposit on the walls of the transparent micro-channel. A two-dimensional profile of the deposit across the channel at selected axial sections is measured. The influences of injection mixture volume on the growth of the thickness of deposited asphaltenes is investigated using two experimental conditions, (i) varying elapsed time at constant flow rate and (ii) increasing the flow rate at a constant elapsed time. In both cases the deposit thickness of asphaltene (δ) increases with the total injection volume (V). The experimental results obtained in this work provide new insights into the deposition process at the micro-scale level, which can be used to facilitate the development of more accurate numerical model for this applicatio
Experimental investigation of Asphaltene deposition in a transparent mini-channel
Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.One of the most recurring flow assurance problems in oil and gas industry is associated to the formation of organic and inorganic deposits in the wellbores and the near-wellbore regions. In particular, the depositions of asphaltene in wellbores represent both a major obstacle for petroleum engineers and a challenging topic for scientists. This paper focuses on experimental investigation of asphaltene deposition in transparent mini-channel. The working fluid is a mixture of heptane and crude oil. Induced by the addition of n-heptane, the dissolved asphaltene in crude oil precipitates to form asphaltene particles which deposit on the walls of the transparent mini-channel at ambient temperature. The thickness of asphaltene deposition is estimated using a visualization technique based on 3D microscopy. The thickness of the deposition layer is quantified and the two-dimensional profile of the deposition at selected axial section is measured. The obtained experimental results provide new insights into the deposition process in micro-scale and will be used to validate a developed numerical model.dc201
Experimental study of asphaltene deposition in transparent microchannels using light absorption method
Heptane-induced asphaltene precipitation from crude oil and its deposition in a vertical transparent microchannel is investigated. The amount of asphaltene deposited on a transparent channel wall is quantified using a non-intrusive flow visualization technique based on reflected light intensity and image analysis. Asphaltene deposits strongly affect the reflected light intensity through the change of mixture color in the recorded images. An empirical equation is developed to correlate the intensity of the light absorption to the thickness of the deposited asphaltene in a transparent microchannel. Non-uniform deposition along the longitudinal direction of the microchannel is also characterized
Permeability correction factor for fractures with permeable walls
Enhanced Geothermal Systems (EGS) are based on the premise that heat can be extracted from hot dry rocks located at significant depths by circulating fluid through fracture networks in the system. Heated fluid is recovered through production wells and the energy is extracted in a heat exchange chamber. There is much published research on flow through fractures, and many models have been developed to describe an effective permeability of a fracture or a fracture network. In these cases however, the walls of the fracture were modelled as being impermeable. In this paper, we have extended our previous work on fractures with permeable walls, and we introduce a correction factor to the equation that governs fracture permeability. The solution shows that the effective fracture permeability for fractures with permeable walls depends not only on the height of the channel, but also on the wall permeability and the wall Reynolds number of the fluid. We show that our solution reduces to the established solution when the fracture walls become impermeable. We also extend the discussion to cover the effective permeability of a system of fractures with permeable walls.R. Mohais, C. Xu, P. A. Dowd, and M. Han
The phase dynamics of spiral turbulence in the Couette-Taylor system
Spiral turbulence observed in Couette-Taylor system
has been characterized using the phase diffusion equation suggested by Hegseth et al. [Phys. Rev. Lett. 62, 257 (1989)]. From space-time diagrams, we have measured the diffusion coefficient, the diffusion velocity, and the turbulent spiral pitch