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Dr. Sourith SISAVATH Ingénieur génie chimique UTC (Université de Technologie de Compiègne, France), Doctor in Petroleum Engineering (Imperial College of London) |
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| E-Mail: s_sisavath@hotmail.com | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Research activities |
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Fundamental pore-scale modelling of a single phase flow through porous sedimentary rocks.
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Supervisors of my PhD thesis |
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Publications |
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Conferences
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Abstracts |
Geometry, percolation and transport properties of fracture networks derived from line data |
S. Sisavath, V. Mourzenko, P. Genthon, J.-F. Thovert and P. M. Adler Geophys. J. Int., Vol. 157, pp. 917-934, 2004. Abstract: In most geological instances, 2-D or 3-D fracture distributions are not available from field data. We show here that when data relative to fractures are collected along a line such as a road or a well, estimations can be given to the major geometrical properties of the corresponding fracture networks, such as the volumetric density of fractures, their percolation character and their macroscopic permeability. All these formulae are analytical and can be split into two parts; the first one can be derived from the measured data, while the second one requires some assumption on the lateral extension of the fractures and on their permeability. All these techniques are applied to fractures located in the Baget watershed. They are also validated on a granite block whose structure is fully known. Extensions are proposed for networks with variable permeabilities and polydisperse fractures. A Simple Model for Deviations from the Cubic Law for a Fracture Undergoing Dilation or Closure Sourith Sisavath, Azzan Al-Yaarubi, Chris C. Pain and Robert W. Zimmerman Pure and Applied Geophysics, Vol. 160, pp. 1009-1022, 2003. Abstract: Experimental observations show that flow through a fracture decreases more rapidly than the cube of the mean aperture (COOK, 1992). In order to provide a possible explanation of these experimental findings, we study creeping flow through a fracture of varying aperture that is symmetric about its midplane, using the power series of the stream function obtained by VAN DYKE (1987) for low Reynolds numbers. For the case of sinusoidally-varying walls, a simple expression relating the effective hydraulic aperture of the channel to the mean aperture and to the amplitude and wavelength of the sinusoidal wall profiles is obtained. Comparison is made to previous studies (KITANIDIS and DYKAAR, 1997) and to finite element calculations, and good agreement is obtained. The effect of fracture closure is then modelled as a decrease of the mean aperture without a change in the roughness. A power law relationship can be obtained between the flowrate and the mean aperture, with an exponent as high as 10, thus providing a potential mechanistic explanation of the experimental findings of PYRAK-NOLTE et al. (1987). Creeping Flow Through an Axisymmetric Sudden Contraction or Expansion Sourith Sisavath, Xudong Jing, Chris C. Pain and Robert W. Zimmerman Trans. ASME J. Fluids Eng., Vol. 124, pp. 273-278, 2002. Abstract: Creeping flow through a sudden contraction/expansion in an axisymmetric pipe is studied. Sampson’s solution for flow through a circular orifice in an infinite wall is used to derive an approximation for the excess pressure drop due to a sudden contraction/expansion in a pipe with a finite expansion ratio. The accuracy of this approximation obtained is verified by comparing its results to finite-element simulations and other previous numerical studies. The result can also be extended to a thin annular obstacle in a circular pipe. The ‘‘equivalent length’’ corresponding to the excess pressure drop is found to be barely half the radius of the smaller tube. Creeping flow through a pipe of varying radius Sourith Sisavath, Xudong Jing, and Robert W. Zimmerman Physics of Fluids, Vol.13 (10), pp. 2762-2772, 2001 Abstract: Creeping flow of a Newtonian fluid through tubes of varying radius is studied. Using an asymptotic series solution for low Reynolds number flow, velocity profiles and streamlines are obtained for constricted tubes, for various values of constriction wavelength and amplitude. A closed-form expression is derived to estimate the pressure drop through this type of tube. The results obtained with this new expression are compared to data from previous experimental and numerical studies for sinusoidally constricted tubes. Good agreement is found in the creeping flow regime for the pressure drop versus flow rate relationship. Our method offers an improvement over the integrated form of the Hagen–Poiseuille equation (i.e., lubrication approximation), which does not account for the wavelength of the constrictions. Laminar Flow Through Irregularly-Shaped Pores in Sedimentary Rocks Sourith Sisavath, Xudong Jing, and Robert W. Zimmerman Transport in Porous Media, Vol. 43, pp. 41-62, 2001. Abstract: Steady-state, laminar flow of an incompressible fluid through prismatic tubes of irregular but constant cross-section is investigated. Several approximations for the hydraulic conductance (Saint-Venant, Aissen, hydraulic radius), some of which were originally proposed for the mathematically analogous problem of torsion of a prismatic elastic bar, are examined and tested for regular geometric shapes for which analytical solutions exist. For such shapes, the Saint-Venant and Aissen approximations are typically within 15% of the exact conductance, whereas the hydraulic radius approximation may be in error by as much as 50%. Conformal mapping and the boundary element method are then used to study the hydraulic conductance of sandstone pores from SEM images of Berea and Massilon sandstone. For these irregular shapes, the hydraulic radius approximation is much more accurate than either the Saint-Venant or Aissen approximation. Moreover, the errors in the hydraulic radius approximation may be of either sign, and thereby partially cancel out when large numbers of pores are considered, whereas the other two methods tend always to overestimate the hydraulic conductance of rock pores. Effect of Stress on the Hydraulic Conductivity of Rock Pores S. Sisavath, X. D. Jing, and R. W. Zimmerman Phys. Chem. Earth A, Vol. 25(2), pp. 163-168, 2000. Abstract: We have made a detailed study of the effect of cross-sectional shape on the hydraulic conductance of rock pores. We consider laminar flow through a single tube with an irregular cross-section; constriction effects, and interconnectedness of pores, will be studied in a future work. We employ three approximate methods: the hydraulic radius approximation, which attempts to correlate the conductivity with the perimeter/area ratio, the Aissen approximation, which utilises a mean value of the conductance of the largest (smallest) circles that can be inscribed (circumscribed) inside (outside) the pore, and the Saint-Venant approximation, which is based on the polar moment of inertia of the shape. The Boundary Element Method is used to provide nominally “exact” estimates of the conductivity, but at the expense of large amounts of computational time. All four methods have been tested on pore shapes from SEM (Scanning Electron Microscope) images of thin-sections of Berea and Massilon sandstone. Surprisingly, the hydraulic radius approximation is the most accurate of the three approximate methods, giving, on average, less than 1% error. Finally, we combine these methods with previous results on the effect of stress on pore deformation, to study the stress-dependence of pore conductivity. |
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