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drillhouston (Petroleum) (OP)
4 Jun 07 12:01
Hi,

If some one can give me an insight into this will be very helpful.

Part 1: GVF = gas void fraction - what are the units for GVF (% or MMCF/BBls)....I am confused!!

Definition for GVF is (Gas volume)/(gas+oil+water); now the question is if GVF is defined in (%) what units do we take the Gas volume in (SCF/MCf or MMcf) and what units do we add up gas, oil & water

Part 2: GOR (Gas oil ratio) = Gas/Oil units (SCF/STB) acceptable

Part 3: GLR (gas liquid ratio) = Gas/(oil+water) and what are the units for this

Please refer to thread : thread469-78612: GVF vs GLR or GOR

Thanks!!!
Helpful Member!  Sebasmagri (Petroleum)
5 Jun 07 9:47
Well drillhouston the GOR and GLR are not dimensional proprerties... but in reservoir and petroleum engineering gas and liquids are studied separately... then there are several units combinations for GOR and GLR depending of the use of that... but the most current units for GOR i.e. are SCF/SB (Standard Cubic Foots / Standard Barrels) and for GLR the same units are used...

GOR = Produced Gas / Produced Oil (Surface Units)
GLR = Produced Gas / Produced Liquids (Surface Units)
Helpful Member!  dhayes (Petroleum)
5 Jun 07 12:31
Depending on the application, GVF is usually the % of the total volume occupied by gas at the conditions being considered.  So GVF is dimensionless - need to calculate the volumes of each fluid phase in same volume units, whether that be gallons, SCF, BBL, etc....

GOR units are usually SCF/STBO - Standard Cubic Feet/Stock Tank Barrels Oil - both at same standard conditions.

GLR is same as GOR, but instead of STBO, you use STBL.
drillhouston (Petroleum) (OP)
6 Jun 07 11:05
Thanks for GVF & GLR/GOR units clarification, Sebasmagri & dhayes!!

It was interesting to know from Sebasmagri as to why do we need GOR/GLR ratios for reservoir engg. purposes treating gas & liquids separately.

Here is the information I have:
Liquid (oil+water) rate = 26500 bbls/d
Gas rate = 1700 mcf/d
assume P = 150 psi
assume T = 120 F

What is the GVF? I used a GLR to GVF calculator and get a GVF of 91.95. Is this correct?

Else what is the preferred way, to convert mcf/d to bbls/d for GVF calculation and how can we do this conversion.

Thanks guys.
DrillHouston
dhayes (Petroleum)
6 Jun 07 11:46
To do this correctly, we would need to know more about the fluids - Oil - oil gravity,
Water - water salinity,
Gas - gas gravity, CO2 mol%, H2S mol%, N2 mol%
Some of the gas will go into solution into the oil and water, and the supercompressibility of the gas also should be considered.  The liquid volume will also be affected by pressure, temperature, and gas absorption.
Also, you give the rates in bbls and mcf, but don't state if these are at standard conditions, or at the pressure and temperature you are specifying.
But for a quick and dirty calculation:
Assume gas is ideal (supercompressibility factor (Z) = 1)and rates are at standard conditions.
Assume standard conditions are 15 psia and 60 deg F.
Calculate volume of gas at 150 psig and 120 deg F:
Use (P1*V1)/(Z1*T1) = (P2*V2)/(Z2*T2)
V2 = V1 * P1/P2 * T2/T1
1,700,000 SCF * 15/(150+15) * (460+120)/(460+60)
 = 172,000 CF
Convert this to bbls  ( 5.615 CF/BBL )
172000/5.615 = 30600 bbls
Without adjusting the liquids volume for compressibility, temperature expansion, or expansion due to gas absorption.

GVR = GV / (GV + LV) = 30600 / (30600 + 26500) =  54%
drillhouston (Petroleum) (OP)
22 Jun 07 13:39
Thanks dhayes,

I really appreciate the quick calculation you have done. Just to add to your reply the "460" value in the aove calculation is to convert F to Rankins.

For our water-cut metering we really need to understand the GVF to understand the application and lot of times the operators themselves are not aware of this value.

But, if i do get a confusing looking information and want to calculate the GVF, I will extend this post.

Best Regards,
DrillHouston

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