6 1_Fluids_EM

Outline

Reservoir Simulation - Fluid Description

Introduction

Etienne MOREAU




Space & Time Discretisation

Reservoir description Fluids’ description Initialisation Aquifer & Well representation Flow description

History matching

• • • • •

Data review

• Space discretisation • Time discretisation • Main features of a flow simulator










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Fluids’ Description: Key Elements

Key Elements

Fluids’ Description

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Main reservoir fluids • Hydrocarbons • Brines

Fluids’ Description: Key Elements

Surface & reservoir conditions. Gas Liquid Equilibriums Physical properties : density, viscosity, compressibility Composition.

Hydrocarbons • • • •

Brines • Surface & reservoir conditions • Physical properties : density, viscosity, compressibility • Composition (salinity).

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Fluids’ Description Surface & Reservoir Conditions

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Surface & reservoir conditions (1)

Surface & reservoir conditions (2)

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Surface

Oil and OilGas

Gas and oil

Surface & reservoir conditions: Oil Production

Reservoir

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Gas and Gascondensates

Condensates often immobiles in the reservoir

Gas and condensates

Surface & reservoir conditions: Condensate Gas

Surface

Reservoir

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Surface

Reservoir

Surface & reservoir conditions: Wet Gas

Gas and Condensates

Gas

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Only Gas

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Surface

Gas Only

Surface & reservoir conditions: Dry Gas

Reservoir

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Bg

Bg + ∆Bg

P + ∆P (∆P Pb

Vo,i

Gaz Vo,2 P2 < Pb

Gaz

S

Vstf

vgpf

Which PVT to choose ?

Vo,f Pf < Pb

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Which PVT to choose ? : Composite PVT

P = Pb

Vo,b

Pi = Initial Pressure Pb = Saturation Pressure Pf = Flowing Pressure

Third step

• Fluid is moving in the reservoir below saturation pressure • Liquid composition versus pressure is identical to a CVD

Second step

• Fluid is moving in the reservoir above saturation pressure • Volume change versus pressure is identical to a CCE

First Step

• Between its original location in reservoir • And its final destination at surface

A fluid Sple will follow a composite path

EP - Reservoir Simulation - Fluids - E.M.













• Fluid has reached the well bore • Volume & composition at surface are identical to a flash.

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SURFACE Standard Conditions : 1 bar, 15 °C Process FOND

Voi Pi

S

Which PVT to choose ? : Composite PVT

vgp3 vgp3

vg f

vgp2

vg 2

vgpb

vg 1

vgpb

S

Vstf

Vo

Vstf

vgpf + Σ vgi

Boc =

Rsc =

Vst3

Vg f

Vst3 S

Vg 2 Vf

Vst2

S

Vg 1 V2 Pf

Vstb S

V1 P2

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Composite PVT (Pf < Pb)

P1

Vstb

Vb Pb

Analytical method (black-oil)

• NO use of simplifying assumptions • Matching of an EOS with lab measurements • Simulation of the composite depletion using the matched EOS

Numerical method

• Numerical method • Analytical method

Two main methods

EP - Reservoir Simulation - Fluids - E.M.










• Use of simplifying assumptions − Liquid & gas composition at surface are constant with time

• Use of basic PVT functions − CCE above saturation pressure − CVD below saturation pressure (in reservoir conditions) − Flash process (from bottom hole conditions to stock conditions)

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Composite PVT (P = Pf = Pb)

Boc(P) = Bopb Rsc(P) = Rspb

Pf

P

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Composite PVT (Pf > Pb)

P

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Vo

Vb

Pb

Rsc(P) = Rspb

Boc(P) = (Vo(P) / Vb) * Bopb

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Composite PVT (Pf < Pb) : Analytical method

Vo Vo VR Vb Vstb Bopb Vstb Bopb Boc = ------ = ----- x ---- x ------ x ------ = Bod x ------- x ------ ~ Bod x ------Vstf VR Vb Vstb Vstf Bodb Vstf Bodb vg vg VR vb Vstb vg Bopb Vb vg Bopb Rsc = ------ = ----- x --- x ------ x ------ = ---- x ------- x ------ ~ --- x ------Vstf VR vb Vstb Vstf VR Bodb Vstf VR Bodb

(vgpb - vgpf) + S vgi Bopb Bopb Rscb - Rsc ~ ------ -------------------- x ---- -- ~ (Rsdb - Rsd) x ------VR Bodb Bodb

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p=process

Pb

;

c=composite

Rsd Rsc

Bod Boc

P

Composite PVT (Pf < Pb) : Analytical method

d=differential

Rspb

Bopb

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