Chapter 7: Properties Of Wet Gases Flashcards
What are the conversion factors for:
a) lb-mol -> scf
b) bbl -> cu ft
a) 1 lb-mol / 380.7 scf
b) bbl / 5.615 cu ft
How many states does a wet gas usually go through when separated?
What are the 3 fluids produced after separation at the surface.
A wet gas typically goes through 2 stages of separation
Fluids produced after separation:
- Stock-tank liquid (condensate)
- Separator gas (SP g)
- Stock-tank gas (ST g)
What is the first step in the conversion of GOR?
Calculate the density and apparent molecular weight of the stock-tank LIQUID
Ma = sum(y * M) API = (141.5 / STO specific gravity) - 131.5
STO specific gravity = STO density / 62.37
How can you estimate the molecular weight of the stock-tank liquid if it is not known?
M(STO) = 5954
_________
(API - 8.8)
Or
M(STO) = (42.43 * STO specific gravity)
___________________________
(1.008 - STO specific gravity)
What is gaseous equivalent and how is it represented in the specific gravity of a reservoir gas equation?
Gaseous equivalent is the volume in scf of a gas that the stock-tank liquid would occupy if it were vaporized
(133,300 * STO specific gravity) / M(STO)
How do you find the specific gravity of the reservoir gas, if the SP gas & the ST gas properties are known?
Specific gravity (res g)
= [R(SP) * SP gas specific gravity + R(ST) * ST gas specific gravity]
__________________________________
R(SP) + R(ST)
R = R(SP) + R(ST)
How do you find the MW of the reservoir gas, if SP & ST gas properties are known?
M(res g) = m(res) / n(res)
= [0.0762R(gas specific gravity) + 350.2(STO specific gravity)] ___________________________________________
0.00263R + [(350.2*STO specific gravity) / M(STO)]
Units = lb of gas / lb-mol of gas
How do you estimate the PRODUCING GOR, if the properties & quantities of all surface gas streams are known?
2-stage: R = R(SP) + R(ST)
3-stage: R = R(SP1) + R(SP2) + R(ST)
What are the 4 steps to calculate the composition of a gas with known surface composition of a wet gas?
- calculate M(STO) & density of stock-tank LIQUID
- convert GORs from
(scf SP gas/STB) => (lb mol SP gas/lb mol STO)(scf ST gas/STB) => (lb mol ST gas/lb mol STO)
- create a table
- calculate mol fraction of the recombined reservoir gas
If given the SP GOR and/or ST GOR, what additional steps do you have to take to find the composition of the recombined res gas?
Convert (scf gas/STB) => (scf gas/STO)
(scf gas/STB) * (1/380.7) * (1/5.615) * [M(STO)/density(STO)]
How do you estimate the specific gravity of the res gas from production data, if the properties & quantities of all surface streams are known?
Find the weighted avg of the specific gravities of the SP gas & ST gas
=[R(SP) * SP spec gravity] +
[R(ST) * ST spec gravity] / [R(SP) + R(ST)]
How do you find the specific gravity of a ST gas that has gone through a 3-stage SP system, if the quantity of the second SP gas is unknown?
= [R(SP1)specific gravity(SP1) + 4600 specific gravity oil + AGP] / R(SP1) + VEQ
What is equivalent volume (VEQ)?
How do you calculate it if GORs, specific gravity(STO), & M(STO) are known?
Where else can you get the VEQ?
The vol of second SP gas & ST gas in scf/STB + the vol (in scf) that would be occupied by a bbl of ST liquid if it were a gas
VEQ = R(SP1) + R(ST) + 133,300*(STO specific gravity) / M(STO)
Can get VEQ value from VEQ Correlation charts
What does addition gas produced (AGP) relate to?
How do you determine the AGP value?
The mass of gas produced from the second SP & ST in a 3-stage separator system
AGP = R(SP2)(SP2 specific gravity) + R(ST)(ST specific gravity)
Can get AGP value from AGP Correlation charts
How do you define the formation volume factor of a wet gas in:
a) words
b) an equation, with units
a) the volume if res gas required to produce 1 STB of liquid at the surface
b) Bwg = V res gas @ res P and T
________________________ ,
V ST liquid @ Std P and T
Scf at res conditions / STB
What are the 4 steps required to calculate Bwg, if surface composition & res conditions are known?
- calculate pseudo critical properties of res gas
- determine z factor & calculate Vm of res gas
- calculate vol of ST liquid condensate from 1 lb mol of res gas
- calculate Bwg
How can you determine the vol of res wet gas required to produce 1 STB of liquid?
What are the units?
vol of res wet gas = R(SP1) + VEQ, (scf/STB)
How do you calculate the molar vol (Vm) of ST liquid?
Vm of ST liquid = M(STO) / STO density
How do you calculate the vol of wet gas in scf?
Bwg = z * [R(SP1) + VEQ] * R T
______________________
380.7 * P
Ideal gas equation of state
What are the 2 simplified equations used to find Bwg in:
a) res cft gas/STB
b) res bbl gas/ STB
a) 0.0282 * z * [R(SP1) + VEQ] * T res scf gas
____________________________ , ___________
P STB
b) a) 0.00502 * z * [R(SP1) + VEQ] * T res bbl gas
_____________________________ , ____________
P STB
What are plant products?
Liquified intermediate hydrocarbons removed from surface gas
How do you find the quantities of liquid product that can be removed from a surface gas (GPM)?
What do you need to know in order to determine these quantities .
Calculations are for individual components
GPM = 19.65 * [ (y * M) / density] , (gal/Mscf)
Or
GPM = 0.3151* [ (y * M) / specific gravity as a liquid], (gal/Mscf)
Must know the composition of the gas
How do you find the density of the ST liquid if given API?
STO density = 141.5 * 62.37
_____________
API + 131.5
