PETE311_06A_Class03_(Maggard)

PETE311_06A_Class03_(Maggard) - RESERVOIR PETROPHYSICS...

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RESERVOIR PETROPHYSICS LABORATORY DETERMINATION OF POROSITY
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Porosity : The fraction of the bulk volume of a rock that is porous. b m b b p V V V V V Porosity = = = φ POROSITY DEFINITION • Porosity is a static property – it can be measured in the absence of flow • Determining effective porosity requires fluid flow to determine if pores are interconnected
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ROCK MATRIX AND PORE SPACE matrix pore space
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MEASUREMENT OF POROSITY 1. Core samples (measure two of: V b , V p , or V m ) 2. Openhole wireline logs
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LABORATORY DETERMINATION OF POROSITY Most methods use small samples (core plugs) multiple samples must be analyzed to get statistically representative results sampling technique is important often all samples are taken from “sweet spots” skewing analysis To determine porosity, measure 2 of 3 volumetric parameters: 1. Bulk volume, V b 2. Matrix volume, V m (also called grain volume) 3. Pore volume, V p
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V V V p m b + = Fraction of volume consisting of pores or voids Fraction of volume consisting of matrix Volume is an extensive property
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MATRIX DENSITIES ( ρ m ) OF TYPICAL PURE COMPONENTS OF RESERVOIR ROCK Lithology Matrix Density (g/cm 3 ) Sandstone 2.65 Limestone 2.71 Dolomite 2.87
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LABORATORY METHODS OF POROSITY DETERMINATION Bulk volume determinations 1. Direct calculation 2. Fluid displacement methods Gravimetric Volumetric – mercury pycnometer ( a precisely calibrated bottle)
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BULK VOLUME BY DIRECT MEASUREMENT Applicable for regularly shaped cores or core plugs Calculate from core dimensions For example; volume of right circular cylinder 4 L d V 2 b π =
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LABORATORY METHODS OF POROSITY DETERMINATION Bulk volume determinations 1. Direct calculation 2. Fluid displacement methods Gravimetric (Archimedes) methods Volumetric – in pycnometer
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ARCHIMEDES METHOD W sat W sub W dry V p = W sat -W dry ρ fluid V m = W dry sub ρ fluid φ = W sat dry W sat sub V b = W sat sub ρ fluid
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EXAMPLE 1 Bulk Volume Calculated by Displacement A core sample coated with paraffin immersed in a container of liquid displaced 10.9 cm 3 of the liquid. The weight of the dry core sample was 20.0 g, while the
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PETE311_06A_Class03_(Maggard) - RESERVOIR PETROPHYSICS...

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