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Type: Conference paper
Title: Free-Fall Gravity Drainage in Fractured Matrix Blocks: Experimental and Network Modeling Simulation Findings and Observations
Author: Mollaei, A.
Haghighi, M.
Maini, B.
Citation: Latin American & Caribbean Petroleum Engineering Conference, 2007: pp.1-17
Publisher: SPE
Issue Date: 2007
ISBN: 1555631851
Conference Name: Latin American & Caribbean Petroleum Engineering Conference (2007 : Buenos Aires, Argentina)
Statement of
Alireza Mollaei, M. Haghighi, and B. Maini
Abstract: <jats:sec> <jats:title>Abstract</jats:title> <jats:p>Free Fall Gravity Drainage as an important recovery mechanism was investigated and analyzed experimentally and by numerical (network model) simulation.</jats:p> <jats:p>Sets of glass micromodels with real pattern of porous media and two numerical network model simulators were prepared in forms of fractured and non-fractured models to study and analyze the Free Fall Gravity Drainage recovery mechanism experimentally and by simulation. After validating the network model simulator, analysis of experimental and simulation results leads to some interesting findings and observations as follow:</jats:p> <jats:p>Based on network modeling simulation, direction of flow through fracture network shows that the oil in the middle horizontal fracture usually flows from one end of fracture to the other end, however in relatively small fracture apertures the oil from both vertical fractures at the ends of middle horizontal fracture flows into the horizontal fracture and then sinks downward to the lower matrix block. This means in relatively small fracture apertures, block to block interaction coefficient (a) reaches to 100%. Another point is that, it was observed from network model simulation data that this critical fracture aperture is a function of pore and throat sizes.</jats:p> <jats:p>Also, experimental and simulation results confirm that there is no break through of gas in free fall gravity drainage process.</jats:p> <jats:p>In addition a new mathematical approach (by means of flow potential and control volume concepts) to block to block interaction effects (Capillary Continuity and Reinfiltration phenomena) is presented to explain and interpret the mechanism of occurrence of these phenomena. This approach proves mathematically that decreasing the fracture aperture leads to increasing the fracture capillary pressure which in turn intensifies the feeding rate of liquid bridge (in the middle horizontal fracture) from upper block and lowers the discharging rate of liquid bridge from lower matrix block. Therefore, the liquid bridge can be more stable between the matrix blocks. As a result, fracture capillary pressure has positive effect on oil recovery from matrix blocks.</jats:p> <jats:p>Finally, a new approach for determination of the matrix block threshold heights at the end of free fall gravity drainage is presented and used to prove that matrix block threshold height inreases with increasing the matrix block height. Also, it will be proved that matrix block recovery factor increases with increasing the matrix block height although matrix block threshold height increases too.</jats:p> <jats:sec> <jats:title>Introduction</jats:title> <jats:p>Multiphase flow in porous media at pore-scale is of great importance in many fields like hydrology, contaminant cleanup and petroleum engineering. Visualization of fluid flow at pore-scale is performed by using glass micromodels and network modeling tries to simulate (model) this physical process by reconstructing the porous media as a network of pores and throats and applying the governing rules to the transport and arrangement of fluids. Macroscopic properties like capillary pressure, electrical resistively or relative permeability can then be estimated across the network 4,5,10,11,16–19. At the first step, visualization and numerical simulation of free fall gravity drainage in single matrix and fractured blocks models was performed by the current authors that has been fully described in the previous paper 12. In the current paper, some of the main experimental and network modeling simulation features and findings of free fall gravity drainage process in fractured blocks model are discussed.</jats:p> <jats:p>Modeling of flow behavior using network models was pioneered by Fatt 1–3 in the 1950s. By distributing the pores and throats on a regular 2D lattice he was able to produce capillary pressure and relative permeability curves for drainage (as a function of average saturation) that had the same characteristics as those obtained experimentally.</jats:p> <jats:p>Laroche 7 et al developed a pore network model to predict the effects of wettability heterogeneities with different patterns and spatial distributions on displacement mechanisms, sweep efficiency, and fluid distribution in gas injection into oil and water. The presented network model simulator in this paper has similar pore and throat shapes to Laroche's network model.</jats:p> </jats:sec> </jats:sec>
Description: Document ID: 107206-MS
Rights: Copyright 2007 Society of Petroleum Engineers
RMID: 0020109004
DOI: 10.2118/107206-MS
Appears in Collections:Australian School of Petroleum publications

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