1 1 Introduction EM

Outline

Reservoir Simulation - Introduction

Data review

• Why run a flow simulation ? • Mathematical & Numerical considerations • ECLIPSE Reminder

Introduction

Etienne MOREAU







History matching

Space & Time Discretisation Reservoir description Fluid description Initialisation Aquifer & Well representation Flow description




Production Forecast

• • • • • •




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EP - Reservoir Simulation - Introduction - E.M.













Introduction Practical use of numerical models started to expand in the sixties related to computer developments. Petroleum companies presently use models : • before making a decision on a new field development • to help in the location of new development wells • before initiating secondary and tertiary processes

Reservoir simulation model is an effective reservoir management tool thanks to the integration of : • specific geological and geophysical works (logs, seismic …) • specific engineering works: laboratory and field (MBA, well test analysis) • production injection data

A necessary synergetic approach leading to integrated reservoir engineering studies.

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EP - Reservoir Simulation - Introduction - E.M.

Introduction Why Run a Flow Simulation?

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Main drivers:

Why run a flow simulation ?

• To overcome simplifying assumptions (used in hand calculations) • To consider realistic problems (development plan, production history, …) • To take into account all the available data and to better understand all the interactions for a given scenario • To perform sensitivity to unknown parameters

Main use:

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Why run a flow simulation ?

• Help to decision, in particular at the end of appraisal phase and during pre-development screening. • Optimise the production profile and the final recovery after production start-up by improving the reservoir description . • Establish of reliable production forecasts.

In all cases

• To integrate history data & to improve reservoir description • To optimise oil production and recovery

Producing reservoir

• To identify efficient recovery mechanisms • To define the well schema & to optimise Capex

Non producing reservoir

• To identify dynamic incertitude • To define appraisal needs (contacts, faults, facies variations)

Appraisal

EP - Reservoir Simulation - Introduction - E.M.













• To establish reliable production forecasts.

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EP - Reservoir Simulation - Introduction - E.M.







Reservoir simulation : Non producing reservoir

define appraisal key points (contacts, faults, facies variations) choose adapted recovery mechanism. define the well number, their location and their geometry. give production profiles to decision makers. appreciate the risks associated to the project.

Some examples : • • • • •

Key points : • The reservoir is very little known. • Some parameters may have a great influence on the reservoir behaviour (permeability, fluid compressibility, mobility ratio, reservoir heterogeneity, …) • It is necessary to appreciate the influence of these parameters on the reservoir behaviour by simulating a large number of runs.

Reservoir simulation : Producing reservoir

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Key points :

• Improve the reservoir characterisation through history matching. • Give production profiles (oil, gas and water flow rates, pressure, fluid composition, …) associated to existing wells. • Define completion changes or infill drilling. • Optimise field capacities (treatment , compressors, …).

Some examples :

EP - Reservoir Simulation - Introduction - E.M.







• Production and recovery optimisation necessitates precise targets; the success of these targets necessitates a high level of confidence in the reservoir description. • History match helps to improve reservoir & flow description. • A large number of runs is necessary to get a satisfactory history match.

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EP - Reservoir Simulation - Introduction - E.M.

Introduction Data Integration

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Phase X

Exploration

X

X

Delineation

X

X

X

Early Dev.

X (in fill wells)

Flow Simulation : Data integration

Coring X X

Maturity

SCAL X

Plateau

O/H Logging

X

X (in fill wells)

X

X

X

X

X

X

X

PBU

X

X

X

X

BHP Survey

X

X

X

RFT

RST

X

X

X

X

Producer PLT

X

X

X

Injector PLT

X

DST

Prod. Allocation

X

X

X

X

X

Studies

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EP - Reservoir Simulation - Introduction - E.M.

Structural model

Flow Model

Upscaling Geostatistics

Sedimentological Model

Flow Simulation : Data integration

Stratigraphic Model

Petrophysical Model

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Construction Field Operations

Production End

Reservoir Uncertainties

Production Start-up

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Time

Weight of decisions & Uncertainties

Basic Engineering

Decision to develop

Pre Project

Development Plan

EP - Reservoir Simulation - Introduction - E.M.

100%

0%

Discovery

EP - Reservoir Simulation - Introduction - E.M.




Introduction Physical Aspects & Basic Laws

Material balance (in each cell)

• relative permeability & capillary pressure

• permeability

Flow (in reservoir conditions)

− Density, Viscosity & Compressibility

• For each phase

− Gas & Liquid Saturations and compositions

• Gas-Liquid Equilibrium

Fluid properties (in reservoir conditions)

• pore compressibility

Reservoir properties

Flow Simulation : Main Modelled Phenomenon's

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EP - Reservoir Simulation - Introduction - E.M.






















Multi phase flow :

One phase flow)

Fluids Compressibility

Fluids Density & Viscosity

Gas Liquid Equilibrium :

Gas Liquid Compositions

Pore compressibility :

Q5

m

Flow Simulation : Basic Laws

;

(y i )

; (z i )

dVp = c p Vp dP

(x i )

;

µ (P )

y i /x i = K i ρ(P )

Qµ ∆x kA

dρ = c f ρ dP ∆(P - ρ g z) = −

i

Q µ ∆(P - ρ g z) = − i i ∆x k kri A i

Q2

Q4

Flow Simulation : Basic Laws

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Material Balance Equation

EP - Reservoir Simulation - Introduction - E.M.




Q1

Q3 Q6 Q1 + Q2 + Q3 + Q4 + Q5 + Q6 = ∆m Flow Term = Accumulation Term

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EP - Reservoir Simulation - Introduction - E.M.










Reservoir (volumetrics)

Flow Simulator : basic parameters − Gross volume : Vt − Net volume : Vu − Porous volume & Pore compressibility : Vp , Cp Pressure: Po, Pg, Pw Saturation : So, Sg, Sw Density : ρo, ρg, ρw Viscosity : µo, µg, µw Compressibility : Co, Cg, Cw Compositions : xi , yi

Fluids : − − − − − −

Flows : − Permeability : k − Capillary pressure : Pcwo = Po - Pw , Pcgo = Pg - Po − Relative permeability : Krow, Krw, Krog, Krg

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Flow Simulator : Different Types

A Flow Simulator also integrates specific features such as :

• Black-oil simulator : One porous medium + black-oil functions • Compositional Simulator : One porous medium + EOS • Dual porosity Simulator : Two porous mediums (matrix and fractures) • Thermal Simulator : Pressure + Temperature equations.

There are several types of Flow Simulator :

EP - Reservoir Simulation - Introduction - E.M.







• Grid Geometry (1D, 2D, 3D, corner point geometry, …) • Pressure drops through tubings and surface network. • Well schedule. • Numerical schemas (discretisation of equations). • Resolution methods (resolution of equations). • Time step management.

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EP - Reservoir Simulation - Introduction - E.M.