Page 16 - Formulas and Calculations for Petroleum Engineering

Reservoir engineering formulas and calculations Chapter 1 9

h: Pay Zone Thickness (ft)
L: Length of Well (ft)
x e : Distance between Horizontal Well and Constant Pressure Boundary (ft)
m o : Oil Viscosity (cP)
k h : Vertical Permeability (mD)
k v : Horizontal Permeability (mD)

Output(s)
c 1 : Dimensionless Constant for calculation (dimensionless)
c 2 : Dimensionless Constant for calculation (dimensionless)
c 3 : Dimensionless Constant for calculation (dimensionless)
c 4 : Dimensionless Constant for calculation (dimensionless)
q c : Dimensionless Critical Rate per Unit length (STB/day/ft)
q o : Critical Rate (STB/day)
z c : Critical Height Representing the Difference between the Apex of the Gas/Water Crest from the Well
Elevation (ft)

Formula(s)
c ¼ 1:4426 + e1
1
c ¼ 0:9439 + e2
2
c ¼ 0:4812 + e3
3
c ¼ 0:9534 + e4
4
0 1
c 2
x
B C
B e C
c
1
0:5
q ¼ c B C
k
@ h A
h
k
v
q
4 0:5 c
q ¼ 4:888 10 D h k *kð Þ L
o r h v
m o
0 1
c 4
x
B C
B e C
c 3 C
0:5
z ¼ c h B
k
@ h A
h
k
v
Reference: Joshi, S.D. 1991, Horizontal Well Technology. Tulsa, Oklahoma: PennWell Publishing Company. Chapter: 7,
Page: 309, 310.
1.17 Crossflow index
Input(s)
N pcf : Oil Recovery from Layered System with Crossflow (STB)
N pncf : Oil Recovery from Stratified System with No Crossflow (STB)
N pu : Oil Recovery from Uniform System with Average Permeability (STB)
Output(s)
CI: Crossflow Index (dimensionless)