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- Zimmerman, R.W., et al.
(författare)
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Non-linear regimes of fluid flow in rock fractures
- 2004
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 41:3, s. 384-384
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Tidskriftsartikel (refereegranskat)abstract
- We have conducted high-resolution Navier-Stokes simulations and laboratory measurements of fluid flow in a natural sandstone fracture. First, epoxy casts were made of the two opposing fracture surfaces. The surface profiles of the two surfaces were then measured at a vertical resolution of ±2 μm, every 20 μm in the x and y-directions, over 2 cm × 2 cm regions of the fracture. These data were then used to create a finite-element mesh for the fracture void space, and the Navier-Stokes equations were solved within this domain. Flow experiments were also conducted within the same fracture casts, over a range of flowrates. The simulations confirm the existence of a weak inertia regime for Reynolds numbers in the range of 1-10, in which the non-Darcy pressure drop varies with the cube of the flowrate. Although of theoretical interest, this effect is, however, probably too small to be of engineering interest. At Reynolds numbers above about 20, both the simulations and experiments exhibit a Forchheimer-type regime, in which the non-Darcy pressure drop is quadratic in the flowrate.
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- Grattoni, C.A, et al.
(författare)
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Polymers as relative permeability modifiers : adsorption and the dynamic formation of thick polyacrylamide layers
- 2004
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Ingår i: Journal of Petroleum Science and Engineering. - : Elsevier BV. - 0920-4105 .- 1873-4715. ; 45:3-4, s. 233-245
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Tidskriftsartikel (refereegranskat)abstract
- Water production from oil and gas reservoirs is increasing worldwide. as more reservoirs are becoming mature. In order to control water production, polymers and gels are often injected into the formation to reduce the water permeability. These systems are known as relative permeability modifiers. Although these methods sometimes lead to significant cost savings, and many successful treatments have been reported, a wider application is hindered by the lack of understanding of the basic mechanisms of permeability modification by polymers. This paper presents some pore-level and basic studies on polymers, with the aim of providing a better understanding of these systems. Experiments have been performed in micro-scale glass flow models, and atomic force microscopy was used to validate the flow observations. The role of adsorption and flow of polyacrylamides in the formation of thick layers is described. The size of statically adsorbed polyacrylamide layers depends on the polymer characteristics (molecular weight, degree of hydrolysis, salinity, etc.), but is less than 250 nm for all the systems studied. On the other hand, dynamically formed polymer layers can reach several thousands of nanometres. The existence of these thick polymer layers is shown here, to our knowledge for the first time, through flow experiments and AFM measurements. While mechanical retention cannot occur under our experimental conditions, the mechanism of adsorption-entanglement gives a reasonable mechanistic description of the dynamic formation of thick layers. The implications of these mechanisms in the modelling of the flow and selection of polymer systems are discussed.
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- Zimmerman, C., Willig, F., Ramakrishna, S., Eichberger, R., Ernstorfer, R., Biswas, N., Storck, W., and Persson, P.
(författare)
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Electronic coupling and coherence effects in ultrafast heterogeneous electron transfer
- 2003
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Ingår i: Ultrafast Phenomena XIII. - : Berlin-Heidelberg, Springer-Verlag. ; , s. 328-330
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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