PETE 310
Lectures #22 & #23
Chapter 11: Pages 317‐19, 321‐22, 326‐333
Liquid Density
Calculated using ideal solution principles (i.e. additive volumes & masses)
Nc
ρ=
∑m
i =1
Nc
i
∑V
i =1
i
Evaluation Methods
Less information
Composition of saturated liquid known (iterative procedure)
Composition of saturated liquid known (correlations)
Solution Gas‐Oil, Gas Composition, and Stock‐
Tank oil gravity known
Solution Gas‐Oil, Gas Specific Gravity, and Stock‐Tank oil gravity known
Problems
C1 & C2 are not liquids at atmospheric conditions
A liquid mixture at reservoir conditions will partially vaporize at standard condition
Solution
Create a fictitious pseudo density for C1 and C2 and for the liquid Pseudo‐densities of C1 & C2
C2
C1
Mixture Density (stc) Apparent liquid densities of C1 and C2
Page 302 (figure 11.2)
ρ a ,C = 0.312 + 0.450 ρ po
1
ρ a ,C = 15.3 + 0.3167 ρ po
2
Equations from Appendix B (starting page 509)
Pressure Correction
ρ (Tsc , PR ) = ρ at (Tsc , Psc ) + Δρ (PR )
47.4 = 45 + 2.4
Temperature Correction
ρ (TR , PR ) = ρ (Tsc , PR ) − Δρ (TR )
From previous plot
47.4 = 45 + 2.4
43.4 = 47.4 ‐ 4
Now follow examples in Excel files provided in our WEB site
Correction using W1, W2
Correction for H2S
42.1 = 43.4 – 1.3
Apparent Liquid Densities of Gases
Consolidate Oil Reservoir Density Calculations
Methods Discussed
Given composition of saturated liquid‐ iterative procedure (guess contribution of C1 & C2) –
Excel file & Ex. 11‐4
Given composition of saturated liquid‐
correlation ‐ using W1 & W2 – Excel file & Ex. 11‐5
Given solution gas‐oil‐ratio, gas composition and stock tank oil gravity (or API) – Excel file & Ex. 11‐6
Consolidate Oil Reservoir Density Calculations
Methods Discussed (cont.)
All these methods evaluate oil density in stages
a) Pseudo‐oil at Tsc, Psc
b) Correct oil density in (a) 1st for reservoir pressure c) Correct density in (b) for reservoir temperature
JCPT paper method & Example 11‐7 of text book
Consolidate Oil Reservoir Density Calculations
JCPT paper method & Example 11‐7 of text book
Both require solution gas‐oil‐ratio, separator gas gravity, API gravity of stok tank, pressure, and temperature
JCPT includes a more current correlation
Both calculate pseudoliquid density at standard conditions and adjust for reservoir pressure and temperature using same equations as in the other methods.
Compare densities from both methods
Oil density is at or below pb
Consolidate Oil Reservoir Density Calculations
Example 11‐7 highlights…
Given data: API, Rs, T, p, γgs Find molecular weight of gas as
Mwg = γ gs × 29
Find mass of gas dissolved in one STB of oil as
Rs
SCF lb − mole
lb
× Mwg [=]
×
×
id
STB
SCF
lb − mole
VM
Find mass of oil in 1 STB as… (your turn!)
Consolidate Oil Reservoir Density Calculations
Example 11‐7 highlights… (more)
Pretend that the oil components are two: stock tank oil & surface gas
Figure 11.8
Consolidate Oil Reservoir Density Calculations
Compare the densities obtained by JCPT procedure with that from Example 11‐7
Discuss results
Different evaluation methods will result in different values of Bo Consolidate Oil Reservoir Density Calculations
The oil formation volume factor is evaluated at or below pb
Bo =
ρSTO + 0.01357 × Rs γ gs
ρOR
How do we evaluate Bo above the bubble point?
For Pressures Above pb
The Oil Density Above Pb
Coefficient of Isothermal Compressibility of Oil (Co)
Why??
Correlations for Co
Above bubblepoint pressure (undersaturated)
Below bubblepoint pressure (saturated)
Co for pressures higher than pb
Co for pressures above pb (Appendix B –
page 522)
Co for pressures below pb
Oil volume will change because of
Pressure Gas in solution ⎡⎛ ∂Bo ⎞
⎛ ∂Rs ⎞⎤ −1
⎟⎟ − Bg ⎜⎜
⎟⎟⎥Bo
Co = − ⎢⎜⎜
⎝ ∂p ⎠⎦
⎣⎝ ∂p ⎠
⎡⎛ ∂Bo ⎞⎛ ∂Rs ⎞
⎛ ∂Rs ⎞⎤ −1
⎟⎟⎜⎜
⎟⎟ − Bg ⎜⎜
⎟⎟⎥Bo
Co = − ⎢⎜⎜
⎝ ∂p ⎠⎦
⎣⎝ ∂Rs ⎠⎝ ∂p ⎠
Co = Bo
−1
⎛ ∂Bo ⎞⎤
⎛ ∂Rs ⎞ ⎡
⎟⎟⎥
⎜⎜
⎟⎟ ⎢Bg − ⎜⎜
⎝ ∂p ⎠ ⎣
⎝ ∂Rs ⎠⎦
Co for pressures below pb
You can evaluate Co using the methods of JCPT paper… Need to have Bg
⎡⎛ ∂Bo ⎞⎛ ∂Rs ⎞
⎛ ∂Rs ⎞⎤ −1
⎟⎟⎜⎜
⎟⎟ − Bg ⎜⎜
⎟⎟⎥Bo
Co = − ⎢⎜⎜
⎝ ∂p ⎠⎦
⎣⎝ ∂Rs ⎠⎝ ∂p ⎠
⎛ ∂Bo ⎞⎤
−1 ⎛ ∂Rs ⎞ ⎡
⎟⎟⎥
⎟⎟ ⎢Bg − ⎜⎜
Co = Bo ⎜⎜
⎝ ∂p ⎠ ⎣
⎝ ∂Rs ⎠⎦
Co for p < pb
Co for pressures below pb (Appendix B)
Bo for pressures below pb
Bo for pressures below pb
These ancient plots are useful to…
Establish ranges of applicability (API, Rs, p…)
Determine trends for the physical properties as a function of p, T, API, etc.
Does Bo increase with Rs?
Does Bo increase with API?
Provide quick estimates (sometimes)
Exercise our visual skills
Total Formation Volume Factor
Oil Viscosity
Viscosity is a measure of the resistance to flow exerted by a fluid
This is called dynamic viscosity and has units of
centipoise = g mass / 100 sec cm
Kinematic viscosity is viscosity / density, units are in centistokes = centipoise /g/cc
Needs of Crude Oil Viscosity
Calculation of two‐phase flow
Gas‐lift and pipeline design
Calculate oil recovery either from natural depletion or from recovery techniques such as waterflooding and gas‐injection processes
Variation of Oil Viscosity Oil Viscosity
T = constant
Gas Out of
Solution
Two Phase Flow
Single Phase Flow
Pb
Evaluation of Oil Viscosity
Evaluate dead oil viscosity (no gas in solution) given oil API and reservoir temperature (Figure 11‐13)
Correct for pressure by “adding gas in solution” (Fig 11‐14)
Most of the oil viscosity correlations are oil dependent (large errors)
Dead Oil Viscosity
Dead Oil Viscosity (Appendix B)
Saturated Oil Viscosity (add gas)
Saturated Oil Viscosity (Appendix B)
Oil Viscosities above pb
Oil Viscosity Above Pb
p> pb
pb
No correction for p =pb
Larger corrections for higher pressures
Viscosity of Undersaturated Black Oils
Viscosity Correlations
Judge These Oil Viscosity Correlations
Judging Correlations…
Judging Viscosity Correlations…
Judging Bubble Point Correlations
Untitled
Correlation Comparison
Bubble Point
3000
Bubble Point, psia
2800
2600
2400
2200
2000
Vazquez and Beggs
Kartoatmodjo
Generalized Standing
1800
Standing
Kaye
Petrosky
Palmer, Poillion and Todd
1600
Mendez
0
Lasater
Osorio
Glaso
Obomanu - Okpobiri
Omoregie
Al-Marhoun
5
10
15
20
Correlation
Reg: CPTC PSS - Chevron Oil Corporation
Viscosity References
Viscosity References
Oil Viscosity References