PNGE 220 – RESERVOIR ROCK PROPERTIES SPRING 2015 - 2016 Porosity Questions 1. Questions A-F will be based on the samples be low – All have the same volume
a) Which sample(s) has the greatest amount of pore space? b) Which sample has the lowest porosity? c) If you were to compare the porosity of Sample A and Sample B, how would the porosities compare? d) Explain your answer to Sample C e) What would happen to the porosities of all samples if they were mixed together? f)
If particles are sorted, as particle size increases, how the porosity of the particles change?
2. A clean, dry sample weighed 20 grams. This sample was saturated in water of density 1.0 g/ 3
cm and then reweighed in air, resulting in an increase in weight to 22.5 grams. The saturated sample was immersed in water of the same density and subsequently weighed 12.6 grams. What is the bulk volume of the sample? 3. A sandstone core plug is 1 inch in diameter, 2 inches long, and has a mass of 56.6 grams. When completely saturated with water, its mass increases to 60.9 grams. Calculate the rock 3
porosity. ρw : 1.00 g/cm . 4. An irregular piece of sandstone is 35.25 grams in mass. When coated with varnish, its mass increased to 36.55 grams. Compute the rock porosity if the coated sample displaces 15.7 ml 3
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of water when fully submerged. ρ g : 2.65 g/cm , ρw : 1.00 g/cm , ρv : 1.80 g/cm .
The varnish coating on the sample was removed and the sample was submerged in water. When air bubbling stopped, the sample was weighed while suspended in water. It weighed 21300 dynes. Calculate the porosity of rock assuming that the rock composition is not known. Compare the porosities obtained from two methods and explain the difference.
5. A clean, dry sample weighed 39.522 grams. This sample was saturated in water of density 3
1.01 g/cm and then reweighed in air, resulting in an increase in weight to 43.797 grams. The saturated sample was immersed in water of the same density and subsequently weighed 24.393 grams. What is the porosity of the sample? 6. The dry sample weighed 20.0 grams. The dry sample coated with paraffin weighed 20.9 3
grams. The density of solid paraffin is 0.9 g/cm . The paraffin coated sample was immersed 3
in a tube and displaced 10.9 cm of liquid. Then the core sample was stripped of the paraffin 3
coat, crushed to grain size, and immersed in a tube and displaced 7.7 cm of liquid. What was the porosity of the sample? Is this effective or total porosity? 7. Calculate the bulk volume of a preserved (paraffin-coated) core sample immersed in water, given the following data: Weight of dry sample in air: 20 grams, 3 Weight of dry sample coated with paraffin: 20.9 grams (density of paraffin is: 0.9 g/cm ), 3 Weight of coated sample immersed in water: 10 grams (density of water is: 1g/cm ) 3 Determine the rock’s porosity, assuming a sand -grain density of 2.67 g/cm . 8. Calculate the bulk volume of a dry core sample immersed in mercury pycnometer, given the following data: Weight of dry sample in air: 20 grams, Weight of mercury-filled pycnometer at 20 C: 350 grams, Weight of mercury-filled pycnometer with the sample at 20 C; 235.9 grams. 3 Density of mercury: 13.546 g/cm .
9. Calculate the effective porosity of a sandstone sample using the following data: Weight of dry sample in air: 20 grams, Weight of saturated sample in air: 22.5 grams, 3 Density of water is : 1.0 g/cm , Weight of saturated sample in water: 12.6 grams. 10. Determine the sandstone’s grain density and porosity, given the following data: Weight of crushed dry sample in air: 16 grams, 3 Weight of crushed sample plus absorbed water: 16.1 grams, (density of water is: 1g/cm ) Weight of water-filled pycnometer: 65 grams, Weight of water-filled pycnometer with the sample: 75 grams. 11. Calculate the porosity of a core sample and estimate the lithology of the sample when the following information is available: Dry weight of sample = 427.3 grams Weight of sample when saturated with water = 448.6 grams 3 Density of water = 1.0 gm/cm
Weight of water saturated sample immersed in water = 269.6 grams Is the porosity effective or total? Why? 12. Calculate the porosity of the sample described below: Mass of dry sample: 104.2 grams, Mass of water saturated sample: 120.2 grams, 3 Density of water: 1.001 g/cm Mass of saturated sample immersed in water: 64.7 grams. Is this effective porosity or the total porosity of the sample? What is the most probable lithology of the matrix material? Explain. o
13. A core sample is saturated with an oil ( ρo : 35 API), gas and water. The initial weight of the 3 sample is 224.14 grams. After the gas is displaced by water ( ρw : 1g/cm ), the weight is increased to 225.90 grams. The sample is the placed in a Soxhlet distillation apparatus, and 3 4.4 cm water is extracted. After drying the core sample, the weight is now 209.75 grams. 3 The sample bulk volume, 95 cm is measured in a mercury pycnometer. 3 Find the porosity and lithology of the core sample. (Notice that the oil density is ρo [g/cm ] = 141.4/(131.5+ ρo [ API]), when the water density at that particular temperature and
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pressure is 1g/cm ) 3
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14. A calibration procedure resulted in V 1 = 100 cm and V2 = 80 cm , respectively. A core sample was placed in the first chamber at 0 kPa pressure. Gas was admitted to the second chamber to a pressure of 413.7 kPa. The valve was open and the final equalized pressure was recorded as 199.783 kPa. What is the grain volume? 3
15. A carbonate whole core (3 inches by 6 inches, 695 cm ) is placed in cell two of a Boyles Law 3 device. Each of the cells has a volume of 1,000 cm . Cell one is pressured to 50.0 psig. Cell two is evacuated. The cells are connected and the resulting pressure is 28.1 psig. Calculate the porosity of the core.
