Calculate reservoir pore volume in field units and initial gas in place?

[marcoskids]

Homework Statement

Calculate reservoir pore volume in field units and initial gas in place for a formation with total bulk volume of 1E8 m^3. A sample of the reservoir gas mixture has
15 moles of CH4 (Tc = 191K),Pc = 46.1bar),
2 Moles C2H6 (Tc =306K, Pc = 48.8 bar)
3 Moles C3H8 (Tc = 370K, Pc - 42.5 bar)

Reservoir pressure at midpoint of production pay zone is 250 bar whilst that corresponding to half pore volume is 206 bars.

Porosity = 0.15. Connate water saturation = 0.25, Reservoir Temperature = 950C

1barrel = 160 litre, 1000 litre = 1m^3, 1ft = 0.3m, 1bar= 0.1 Mpa

R = 8.314 Kpa*m^3 / kgmole*k

K = degrees C + 273, βg = 3.74E-4Z(T/P), T in K and P in Mpa

Homework Equations

Real gas law = PV = ZnRT
RVpore = Vb*Rf
Gas in place = (Vb*Rf (1-sw)*$\phi$) / Bo

The Attempt at a Solution

I know that pore volume = Recovery factor * bulk volume. Bulk volume is given but Rf isn't

I have found z and think its important but I don't know where to use it

N yi mw mwyi pi pi yi ti ti yi

ch4 15 0.75 16 12 46.1 34.575 191 143.5
C2H6 2 0.1 30 3 48.8 4.88 306 30.6
C3H8 3 0.15 44 6.6 42.5 6.375 370 55.5
20 MWg 21.6 45.83 229.6
pres 206 Tr 1.6
z 0.82
Any help please!

 

[anathema]

Hi there! Thank you for reaching out. I can help you with your problem.

To calculate the reservoir pore volume, you will need to use the formula RVpore = Vb*Rf, where Vb is the bulk volume (given as 1E8 m^3) and Rf is the recovery factor. The recovery factor is a measure of the amount of oil or gas that can be extracted from the reservoir, and it is typically estimated based on the properties of the reservoir and the production methods used. In this case, the recovery factor is not given, so you will need to do some research or make an assumption based on similar reservoirs to estimate it.

To calculate the initial gas in place, you will use the formula Gas in place = (Vb*Rf*(1-sw)*φ)/Bo, where sw is the connate water saturation (given as 0.25), φ is the porosity (given as 0.15), and Bo is the formation volume factor which is a measure of how much the gas expands when it is brought to the surface. In this case, Bo is not given, so you will need to do some research or make an assumption based on similar reservoirs to estimate it.

You have correctly calculated the z factor for the gas mixture using the given data. The z factor is important because it accounts for the non-ideal behavior of real gases at high pressures and low temperatures. You will need to use the z factor in the real gas law equation PV = ZnRT to calculate the reservoir pressure at the midpoint and at half pore volume. Then, you can use these pressures in the formula for Gas in place to calculate the initial gas in place.

I hope this helps! Let me know if you have any further questions. Good luck!