05-Capillary Pressure - Capillary Pressure Instructional...

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Capillary Pressure 1 Capillary Pressure Instructional Objectives: - List four uses of capillary pressure data. - Define hysteresis. - Sketch capillary pressure curves for typical drainage and imbibition processes. - Explain the relation between capillary pressure data and reservoir fluid saturation. - Define oil-water and gas-oil transition zones. - Convert capillary pressure lab data to reservoir conditions. - Define the J -function. - List four different methods for measuring capillary pressure in the lab. Uses of Capillary Pressure Data: - Determine initial water saturation in the reservoir. - Determine fluid distribution in the reservoir. - Determine residual oil saturation for water flooding applications. - Determine pore size distribution index. - May help in identifying zones or rock types. - Input for reservoir simulation calculations. Capillary pressure measurements determine the initial water saturation. This is the saturation at which the increase in capillary pressure does not affect the saturation. Capillary pressure data can also determine the vertical fluid distribution in the reservoir by establishing the relation between the capillary pressure and height above the free water level. Imbibition capillary pressure measurements determine the residual oil saturation in water flooding operation. We can infer the pore size distribution index, λ , from capillary pressure data. This index can be used to calculate relative permeability using industry correlations. Capillary pressure curves are similar for the same rock type. The shape also gives indication about the rock permeability. Capillary pressure curves are used to initialize simulation runs and in flow calculations between grid blocks. Capillary Pressure Concept: AB ρ o ρ w 1 2 3 P c = 0 Pressure Depth ρ w ρ o Water exists at all levels below 2, and both water and oil exist at all levels above 2.
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Capillary Pressure 2 Oil and water pressure gradients are different because their density is different. At level 2, pressure in both the water and oil phases is the same. At any level above 2, such as level 3, water and oil pressures are different. This difference in pressure is called the capillary pressure . Capillary Pressure Definition: - The pressure difference existing across the interface separating two immiscible fluids. - It is usually calculated as: P c = p nwt - p wt One fluid wets the surfaces of the formation rock (wetting phase) in preference to the other (non- wetting phase). Gas is always the non-wetting phase in both oil-gas and water-gas systems. Oil is often the non-wetting phase in water-oil systems. Example: Define capillary pressure in the following systems: - Water-gas system. - Water-wet water-oil system. - Oil-gas system. Solution: - water-gas system: P c = p g - p w - water-wet water-oil system: P c = p o - p w - oil-gas system: P c = p g - p o Relation between Capillary Pressure and Fluid Saturation: Free Water Level P c P d Water-oil contact H d Height Above Free Water Level (Feet) 05 0 1 0 0 S w (Percent) 0 50 100 S w (Percent) 0
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Capillary Pressure 3
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This note was uploaded on 06/12/2010 for the course PETROLEUM 1500 taught by Professor Ahmedalbamby during the Spring '10 term at University of Texas at Austin.

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05-Capillary Pressure - Capillary Pressure Instructional...

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