Modelling of flooding processes

This section illustrates how Pyscal is intended to be used in various drainage/injection scenarios.

The notation WOGn for each case is a bookkeeping system for the flooding processes. The positions in the letter triplet are fixed and reserved for water, oil and gas. The letter used in each position states the phase-saturation change, D for decreasing, I for increasing and C for constant. The trailing number is the cycle number.

In the figures below, the dashed orange line and the arrows indicate the initial state for the relevant flooding process, and the saturation direction.

Water injection in oil field (IDC2)

Pyscal	Eclipse	Comment
SWL	SWL
SWCR	SWCR	Critical water. Equal to SWL or SWL + 0.01 if this improves simulation performance
SORW	SOWCR	Residual oil
KROEND	KRO	kro @ SWL
	KRORW	Not used in Pyscal (kro @ SWCR)
KRWEND	KRWR	krw @ SORW
KRWMAX	KRW	Usually set to 1

Gas injection or solution gas drive (CDI2)

Pyscal	Eclipse	Comment
SWL	SWL
SORG	SOGCR	Residual oil
SGCR	SGCR	Critical gas
KRGEND	KRGR	krg @ SORG
KRGMAX	KRG	Usually 1
KROEND	KRO
	KRORG	Not used in Pyscal
krgendanchor=sorg
SGRO=0

Dry gas field (invading water) (ICD2)

This scenario is for a two-phase Eclipse simulation. If condendsate dropout can occur it should be modelled as a three-phase simulation.

Pyscal	Eclipse	Comment
SWL	SWL	Initial state
SWCR	SWCR	Critical water, when water becomes mobile. Usually set epsilon higher than SWL.
SGRW	SGCR	Trapped gas/residual gas. SGCR must be set equal to SGRW
SGL	SGL	Set to zero
KRGEND	KRG	Usually 1
	KRGR	Not to be used.
KRWEND	KRWR
KRWMAX	KRW

Wet gas/condensate field (ICD2, CID2, IDC2)

This field scenario is for a three-phase reservoir simulation allowing for condensate dropout (oil displacing gas) in addition to water displacing both gas and oil. The figure below illustrates different regions and processes in a wet gas/condensate field.

The following processes are associated with the regions depicted in the figure above:

Region	Process
1	ICD2
2	ICD2 & CID2
3	CID2 & IDC2

Three-phase consistency requirements:

• SWL: The same input must be used for all three flow scenarios.

• The following relationships must hold: SGRW = SGCR = SGRO = SORW

The processes are described in the following figures:

Water displacing gas (ICD2)

This is the main process for a gas/condensate field.

Pyscal	Eclipse	Comment
SWL	SWL	Initial state
SWCR	SWCR	Critical water, when water becomes mobile. Usually set epsilon higher than SWL.
SGRW	SGCR	Trapped gas/residual gas. SGCR must be set equal to SGRW
SGL	SGL	Set to zero
KRGEND	KRG	Usually 1
	KRGR	Not to be used.
KRWEND	KRWR
KRWMAX	KRW	Usually 1

Oil displacing gas (CID2)

This is the process for condensate dropout.

Pyscal	Eclipse	Comment
SORG	SOGCR	Critical oil
SGCR	SGCR	Residual gas/trapped gas. Must equal SGRO
SGRO		Must equal SGCR
KRGEND	KRG	Usually set to 1
KRGMAX		Not used. Leave defaulted at 1
KROGEND	KROR	Kro at trapped gas in a three-phase system
KROMAX	KRO	Usually set to 1

Water displacing oil (IDC2)

Pyscal	Eclipse	Comment
SWL	SWL
SWCR	SWCR	Critical water. Equal to SWL or SWL + 0.01 if this improves simulation performance
SORW	SOWCR	Residual oil
KROWEND	KRO	kro @ SWL in in a three-phase system
	KRORW	Not used in Pyscal (kro @ SWCR)
KRWEND	KRWR	krw @ SORW
KRWMAX	KRW	Usually set to 1

CO₂-injection (gas displacing water, DCI1)

Pyscal	Eclipse	Comment
SWL	SWL	Residual water (“SWR”)
SWCR	SWCR	Residual water. Set equal to SWL
SGCR	SGCR	Critical gas.
SGRW	SGL	Set to 0
KRGEND	KRG
KRWEND	KRW	Usually set to 1

CO₂ trapping (ICD2)

Process is analoguous to “Dry gas field”.

Pyscal	Eclipse	Comment
SWL	SWL	Residual water (“SWR”)
SWCR	SWCR	Residual water. Set equal to SWL
SGCR	SGCR	Trapped gas. Must equal SGRW
SGRW	SGCR	Set to SGCR
KRGEND	KRG
KRWEND	KRWR	Usually set to 1

Oil paleo zone (IDC1)

In an oil paleo zone, the saturation starts at sorw. socr (critical oil saturation) must be larger than sorw. The swcr parameter is to be interpreted as residual water.

Pyscal	Eclipse	Comment
SWL	SWL
SWCR	SWCR	Residual water. Set equal to SWL
SORW	SOWCR	“Initial” oil
SOCR		Critical oil saturation. SOCR > SORW.
KRWEND	KRWR
KRWMAX	KRW	Usually set to 1

Gas paleo zone (DCI3)

Pyscal	Eclipse	Comment
SWL	SWL	Residual water, SWCR must be set equal
SGL	SGL	Initial gas saturation
SGCR	SGCR	Critical gas, must be larger than SGRW
SGRW	SGL	Must be set equal to SGL
KRGEND	KRG	Krg at residual water
KRWEND	KRW	Krw at initial gas saturation
KRWMAX		Not in use. Leave defaulted.