Microscale Visual Study of End Effects at Permeability Discontinuities |
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Authors: | Richard A Dawe Albert Caruana Carlos A Grattoni |
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Institution: | (1) Department of Geosciences, University of Oslo, Oslo, Norway |
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Abstract: | The physical effect of multiphase fluid distribution and flow at permeability boundaries has not been fully investigated,
particularly at the pore scale (1–100 μm), although such behaviour can significantly affect the overall scaled-up reservoir
trapping capacity and production performance. In this article, microscale physical models have been used to qualitatively
study the pore scale flow events at permeability boundaries, both high to low and vice versa, to gain a better understanding
of the role of these boundaries and water saturation on multiphase displacement behaviour at the pore scale. We have used
etched glass models of stripes of large and small (a factor of two) pores with circular matrix. Capillary pressure, which
is the controlling parameter is itself dependant on pore size and its spatial distribution, the magnitude of the interfacial
tensions and the wettability between the fluids and the solid surface of the models. Sometimes, the only way the non-wetting
fluid can penetrate the boundary is through a fortuitous leakage, whereby the presence of an initial saturation reduces the
controlling capillary pressure. Examples are demonstrated including mechanisms of end-effects and how capillary boundary resistance
(due to capillary forces) can be broken down and fluid movement across the boundary can develop. These micromodel experiments
show vividly that connate water can assist in these processes, particularly oil trapping and leakage of water across a permeability
boundary. |
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