2- A cylindrical core with 2 cm diameter and 10 cm length weights about 78.5 gra

Question

2- A cylindrical core with 2 cm diameter and 10 cm length weights about 78.5 gram when it is clean and dry. When you fully saturate the core with water it weighs 86.4 gram. Assume water density 1.05 g/cc .

a) Calculate the porosity of the core sample? (25 points)

b) What type of porosity you measured with this method? Explain. (10 points)

c) Calculate the density of the rock?(10 points)

3- Using the same core sample from question 2, injecting water with a rate of 5 cc/s will result in 42 atm pressure drop across the coreholder. Assume water viscosity is 1 centipoise.

a) Calculate the permeability of this core sample. Use the Darcy equation from your textbook. (15 points)

b) What type of permeability you calculate in part 1. Explain. (10 points)

4- If flushing the same core sample from question 2 with oil results in producing 6 cc of water out of the core, what would be the water and oil saturation in the core sample? (20)

Explanation / Answer

2. we know that porosity = volume of the empty space in object/total volume *100%

now volume of the empty cylinder= pie*R^2*H=3.14* 1*10 cm^3=31.4cm^3

from the given weight 78.5gm we get the density of the rock= 78.5/62.8gm/cm^3=1.25gm/cm^3 c)

now when we pour water the weight become 86.4gm

so the total volume= 86.4/(1.05+1.25)=86.4/2.3= 37.5cm^3

Therefore porosity= 31.4/37.5 *100%= 83.7%

b) there are three major types for measuring porosity. In case of primary porosity measurement we measure the empty space in the object created by the object itself. Secondary porosity mesurement is slightly different from previous one. In this case the empty space is measured during the formation of the rock using cracks, stress values. Finally, effective porosity is measured using some secondary fluid like air/water etc. So we measure effective porosity in this example.

3a) we know that Darcy equation relates pressure drop, permeability , viscocity and flow rate in a single expression.

Therefore we use Q=kA*Pd/L where Q= flow rate,k=permeability ,A= area of the rock, Pd= pressure drop,=viscocity

using values 5=k*3.14*1^2*42/.01*10 or k= .003791

b) In this case single phase fluid is flowing through the empty space of the rock and per Darcy's law we knoww that for single phase fluid absolute permeability is measured wwhich is also famous as single phase permeability. So here absolute permeability is measured.

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