Chapter 22
Introduction to Reservoir Modelling
Jan C. Rivenæs, Petter Sørhaug and Ragnar Knarud
22.1 Introduction
This chapter gives the reader an overview of the basic
elements in reservoir modelling.
Reservoir modelling is the process of transferring
the available subsurface data and knowledge into a
digital (computerised) numerical representation of
the subsurface, and is now considered an essential
part of understanding and developing oil and gas
resources. Reservoir models are used for calculation
of initial volumes in place, optimisation of drainage
strategy for a hydrocarbon field, calculation of
recoverable volumes, generation of production
profiles, evaluation/generation of depletion plans,
and as a planning tool for detailed placement of
production and injection wells. Due to the multidisciplinary input and the increased options for
advanced visualisation, digital 3D geological models
are important as a collaborative working tool for the
integration of different subsurface disciplines
(Figs. 22.1 and 22.2).
Digital reservoir models may serve different
purposes, and we typically distinguish between static
reservoir models and dynamic reservoir models.
22.1.1 The Static Reservoir Model
The static reservoir model is usually referred to as the
geological model (often abbreviated “geomodel”), and
is a digital numerical model describing the initial state
of the reservoir before any production of hydrocarbons
has taken place, i.e. representing the spatial distribution
of rock types with different reservoir properties. Hence,
a major task for the static model is calculating the initial
in-place volumes of hydrocarbons, which is a quantification of what is “down there”, without consideration of
recovery method or economical viability. These volumetric calculations can be performed for an entire reservoir or individually for any layers or fault segments
that have been defined during model construction.
22.1.2 The Dynamic Reservoir Model
The dynamic reservoir model is typically based on the
framework and spatial distribution of reservoir
properties from the static reservoir model. Equations
for fluid flow in porous media are applied in order to
simulate the distribution/movement of reservoir fluids
as a function of production and/or injection. The
dynamic reservoir model also takes into account
changes related to varying reservoir pressure and
hydrocarbon saturation as a function of production/
injection over time. Fluid properties, such as density,
viscosity, phase equilibrium and fluid mobility, interact
with changes in pressures and fluid saturations.
To summarise, the static model will estimate the
natural in-place volumes in the subsurface, while the
dynamic model will predict what is recoverable. What
J.C. Rivenæs (*) P. Sørhaug R. Knarud
Statoil Norway
e-mail: jriv@statoil.com; pesor@statoil.com; ragk@statoil.com
K. Bjørlykke (ed.), Petroleum Geoscience: From Sedimentary Environments to Rock Physics,
DOI 10.1007/978-3-642-34132-8_22, # Springer-Verlag Berlin Heidelberg 2015
559
Introduction to Reservoir Modelling
Jan C. Rivenæs, Petter Sørhaug and Ragnar Knarud
22.1 Introduction
This chapter gives the reader an overview of the basic
elements in reservoir modelling.
Reservoir modelling is the process of transferring
the available subsurface data and knowledge into a
digital (computerised) numerical representation of
the subsurface, and is now considered an essential
part of understanding and developing oil and gas
resources. Reservoir models are used for calculation
of initial volumes in place, optimisation of drainage
strategy for a hydrocarbon field, calculation of
recoverable volumes, generation of production
profiles, evaluation/generation of depletion plans,
and as a planning tool for detailed placement of
production and injection wells. Due to the multidisciplinary input and the increased options for
advanced visualisation, digital 3D geological models
are important as a collaborative working tool for the
integration of different subsurface disciplines
(Figs. 22.1 and 22.2).
Digital reservoir models may serve different
purposes, and we typically distinguish between static
reservoir models and dynamic reservoir models.
22.1.1 The Static Reservoir Model
The static reservoir model is usually referred to as the
geological model (often abbreviated “geomodel”), and
is a digital numerical model describing the initial state
of the reservoir before any production of hydrocarbons
has taken place, i.e. representing the spatial distribution
of rock types with different reservoir properties. Hence,
a major task for the static model is calculating the initial
in-place volumes of hydrocarbons, which is a quantification of what is “down there”, without consideration of
recovery method or economical viability. These volumetric calculations can be performed for an entire reservoir or individually for any layers or fault segments
that have been defined during model construction.
22.1.2 The Dynamic Reservoir Model
The dynamic reservoir model is typically based on the
framework and spatial distribution of reservoir
properties from the static reservoir model. Equations
for fluid flow in porous media are applied in order to
simulate the distribution/movement of reservoir fluids
as a function of production and/or injection. The
dynamic reservoir model also takes into account
changes related to varying reservoir pressure and
hydrocarbon saturation as a function of production/
injection over time. Fluid properties, such as density,
viscosity, phase equilibrium and fluid mobility, interact
with changes in pressures and fluid saturations.
To summarise, the static model will estimate the
natural in-place volumes in the subsurface, while the
dynamic model will predict what is recoverable. What
J.C. Rivenæs (*) P. Sørhaug R. Knarud
Statoil Norway
e-mail: jriv@statoil.com; pesor@statoil.com; ragk@statoil.com
K. Bjørlykke (ed.), Petroleum Geoscience: From Sedimentary Environments to Rock Physics,
DOI 10.1007/978-3-642-34132-8_22, # Springer-Verlag Berlin Heidelberg 2015
559