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1. MATERIAL BALANCE
EQUATIONS
Eng/ Mohamed Hamed Yassin
Email: Mohamed.H.Yassin@Hotmail.com

2. AGENDA
Types of Reservoirs and Driving Mechanisms
Calculations of Material Balance Equations
MBAL Software Applications

3. Types of Reservoir
Fluids
Gas Reservoirs
Without
Bottom-Water Drive
With
Bottom-Water Drive
Oil Reservoirs Water Reservoirs

4. Oil Reservoirs
Saturated
P <= Pb
Solution Gas
Drive
Gas-Cap
Drive
Bottom-Water
Drive
Combination
Drive
Undersaturated
P > Pb
Without
Bottom-Water Drive
With
Bottom-Water Drive

5. CALCULATION OF ORIGINAL
HYDROCARBON IN PLACE (HIIP)
Volumetric Method
Material Balance Equations (MBEs)
Decline Curve Analysis

6. CALCULATION OF HIIP
(VOLUMETRIC METHOD)
)1(. wiSBVN  
)1()( wiSAh  
oi
wiSAh


615.5
)1(43560 

oi
wiSAh
N

 )1(7758 

gi
wiSAh
G

 )1(7758 

STB
SCF
SCFBblg
STBbblo
acresA:
fth:
fractionsSwi :,

7.     gasfreeBwWBNNGBNB wpeopgioi 
    
   gig
gi
oi
gssioio
wpegspop
BB
B
mB
BrrBB
BwWBrRBN
N



  ppspsi RNrNNNrGgasfree 
       gppspsiwpeopoioi BRNrNNNrGBwWBNNmNBNB 
(N-Np)Bo
free gas
PPi
oi
gi
NB
GB
m 
CALCULATION OF OOIP BY MBE
(SATURATED RES)
Pi
giGB
oiNB
We
(We-WpBw)

8. CALCULATION OF OOIP BY MBE
(SATURATED RES)
        egig
gi
oi
gssioiowpgspop
WBB
B
mB
NBrrBBNBwBrRBN 






eg
gi
oi
o WE
B
mB
ENF 






g
gi
oi
o
e
g
gi
oi
o E
B
mB
E
W
N
E
B
mB
E
F




This equation includes 3 unknown (We, m & N)
Re-arrange this equation as a straight line equation
If We is assumed to be known and m is calculated
by geological data , N can be obtained
g
gi
oi
o E
B
mB
E
F

g
gi
oi
o
e
E
B
mB
E
W

o
45
N

9. CALCULATION OF OOIP BY MBE
(UNDERSATURATED RES)
By Considering the Cw and Cf
pCB
BN
N
eoi
op


Use MBE as a straight line as follows:
PCNBBN eoiop 
oNEF 
op BNF 
N
PCBE eoio 