Initial Condition

P(x,0) = Pi

x

y

z

For simulation)

oz

k,j,iz(

op

n

k,j,ip

Po @ zo

Zo – datum depthPo – initial pressure at datum depth

Initial Condition

x

y

z

Initialization in Simulator

1. Direct input into each gridblock

Use keywords (for black oil):PRESSURESWATSGASRS or PBUB

Gas

oil

Wtr

Initial Condition

x

y

z

How initialize phase pressures and saturations; i.e., oil, gas, water?

Initialization in Simulator2. Calculated by equilibration - initial conditions determined on the basis of

hydrostatic equilibrium (EQUIL)

Data requirementsa. Pressure at datum depthb. Gas-oil and water-oil contactsc. Capillary pressure at each contactd. Rs or Pb optional as f(D)

Initial Condition

Sw P P

pw (also po, pg)

po (also pw, pg)

pg (also po, pw)

z

pw

pw

pw

po (also pg)

po (also pg)

po

pg

Oil+Wtr pcow0

Water

Gas

OIL

0pcog

zones

A

B

C

D

E

VerticalSaturationdistribution

VerticalPhase pressure

DistributionsIncluding Pc

VerticalPhase pressure

Distributionsneglecting Pc

Gas+Oil

Initial Condition

• Zone A – Gas Cap

– Gas phase is only continuous phase, thus

– With So = 0, we can find,

– Also Sw = Swi, thus

– And last, Sg = 1 – So - Sw

gdz

gdp

maxg

Scog

pg

po

p

)wi

S(cow

po

pw

p

Initial Condition

• Zone B – Oil/Gas Transition

– Both oil and gas phases are continuous, thus

– From the oil and gas pressures, find Pc

– Which allows the determination of gas saturation distribution

– Also Sw = Swi, thus

– And last, So = 1 – Sg - Sw

odz

odp

andgdz

gdp

op

gp

gS

cogp

)wi

S(cow

po

pw

p

Initial Condition

• Zone C – Oil Zone

– oil phase is only continuous phase, thus

– With Sg = 0, we can find,

– Also Sw = Swi, thus

– And last, So = 1 – Sg - Sw

odz

odp

)0(cog

po

pg

p

)wi

S(cow

po

pw

p

Initial Condition

• Zone D – Oil/water Transition

– Both oil and water phases are continuous, thus

– From the oil and water pressures, find Pc

– Which allows the determination of water saturation distribution

– Also Sg = 0, thus

– And last, So = 1 – Sg - Sw

odz

odp

andwdz

wdp

wp

op)

wS(

cowp

)0(cog

po

pg

p

Initial Condition

• Zone E – water Zone

– water phase is only continuous phase, thus

– With So = 0, we can find,

– Also Sg = 0, thus

– And last, Sw = 1

wdz

wdp

)max,w

S(cow

pw

po

p

)0(cog

po

pg

p

Initial Condition

Example: Initialization of Tutorial 2

x

y

zzo= 3000m

Pa =337.582 bar

Po=331.65 bars

WOC = 3085m Pcow=0 bars

GOC = 3000m Pcog=0 bars

Aquifer datum depth = 3113.2m