PCB3053
RESERVOIR MODELLING AND SIMULATION
MAY 2015
Dr. Mohammed Abdalla Ayoub
Ch. 1.1: Introduction to Reservoir Simulation
Petroleum Engineering Department (GPED)
Outline
• Today’s class presentation will cover the following:
• Brief introduction about reservoir modeling and simulation.
1- Reasons to perform reservoir modeling.
2- Types of Computer Modeling
3- Simulation approaches.
4- Types of Numerical Models.
5- Modeling Concepts
6- Reservoir Simulation Steps.
• Reservoir simulator classifications
• Why it is accepted?.
• Introduction To Commercial Reservoir Simulators
Introduction
Reservoir modeling
Is often defined as
the allocation of resources to optimize hydrocarbon
recovery from a reservoir while minimizing capital investments and
operating expenses.
• The
primary objective
in a reservoir management study is to determine the
optimum conditions
needed to maximize the economic recovery of
hydrocarbons from a prudently operated field.
• Reservoir modeling
is the most sophisticated methodology available for
achieving the
primary reservoir management objective
.
Introduction, cont…,
Reasons to perform a model study:
• Several reasons to perform a model study. From a commercial
perspective, is the ability to generate cash flow predictions.
From two perspectives:
1-
corporate impacts
Cash Flow Prediction
Need Economic Forecast of Hydrocarbon Price
2-
Reservoir Management
Maximize the economic recovery of hydrocarbon.
Minimize the operation expenses
History Matching
Prediction
Geological Model
Reservoir Simulation Model
Reduce Operation Expenses
Increase Recovery
Introduction, Cont…,
Introduction, cont…,
Need Data !
John, R. Fanchi Principles of Applied Reservoir Simulator
Available Data
Not Enough Data:
–
Analogy with other
reservoirs
–
Correlation
–
Assumption
Introduction, cont…,
Gridding
• Honor geology
• Preserve numerical accuracy
• Be easy to generate
Gurpinar, 2001
Wolfsteiner et al., 2002
Prevost 2003
Introduction, cont…,
Reservoir Sampling and Scales
Soft Data:
Seismic Data related to interpretation
Hard Data
: Core and well log measurements
Conceptual scales:
Giga scale
Include information associated with
geophysical
techniques,
such as reservoir architecture
Mega scale
Deals with
reservoir characterization
and it includes well
logging, well testing and 3D seismic analysis
Macro scale
Core analysis
and
fluid property
analysis
Micro scale
Includes
pore scale data
obtained from techniques such as thin
section analysis and measurement of grain size distribution
Introduction, cont…,
Upscaling
There are many techniques and levels, which are available for
upscaling purpose. Make sure to select the best and optimum
level of and techniques to minimize the associated errors
Gurpinar, 2001
Summary
To summarize the need for reservoir simulation :
•
To obtain accurate performance predictions for a hydrocarbon reservoir under
different operating conditions.
•
In a hydrocarbon-recovery project (which may involve a capital investment of
hundreds of millions of dollars), the risk associated with the selected development
plan must be assessed and minimized.
Factors contributing to the risk:
1. The
complexity
of the reservoir because of heterogeneous and anisotropic rock
properties;
2. Regional variations
of fluid properties and relative permeability characteristics;
3. The
complexity
of the hydrocarbon- recovery mechanisms; and
4. The
applicability of other predictive
methods with limitations that may make them
inappropriate (can be controlled through proper use of sound engineering practices
and judicious use of reservoir simulation).
Reservoir Simulator
Reservoir simulators are
computer programs
that
solve
the equations for
heat
and
mass flow
in porous media, subject to appropriate
initial
and
boundary conditions
.
The number and type of equations to be solved depends on:
geological characteristics of the reservoir (single or double
porosity),
characteristics of the oil, and
oil recovery process to be modeled.
Types of Computer Modeling
The reservoirmodel Fluid flow Equation within the reservoir. The reservoir is modeled by subdividing the reservoir
volume into an array, or grid, of smaller volume elements, which called: gridblock, cell, or node.
The well model Fluid flow that represents the extraction of fluids from the reservoir or the injection of fluids into
the reservoir.
The well bore mode
Fluid flow from the sand face to the surface
The surface
Simulation Approaches
Broadly classified, there are two simulation approaches we can take:
analytical
(Physical) and
numerical
(mathematical).
The analytical approach, as is the case in classical
well test analysis
,
involves a great deal of
assumptions
—in essence, it renders an exact
solution to an approximate problem.
The numerical approach, on the other hand,
attempts to solve
the more
realistic problem with
less stringent assumptions
—in other words, it
provides an
approximate
solution to an exact problem.
The Simulation Process
Recovery
process
Nonlinear PDE
Nonlinear
Algebra
Equations
Solution starts
here!!!
linear Algebra
Equations
Pressure, Saturation
Distributions,
and Well Rates
Numerical Reservoir
Types of Numerical Models
Black oil
Compositional
Chemical flood
Thermal
Dual porosity (fracture)
Gas model (gas gathering system)
Types of Numerical Models, cont…,
Black oil model
Depletion Water Injection
o Component: oil water gas o Phase: Oil water gas
Gas injection to increase or maintain reservoir pressure
Miscible flooding as the injection gas goes into solution with oil Carbon dioxide flooding, with the gas soluble in both oil and water Thick reservoirs with a compositional gradient caused by gravity Reservoirs with fluid compositions near the bubble-point
High-pressure, high temperature reservoirs Natural-fracture reservoir modeling.
o Component: C1,C2, ….So2, H2S, N2,.. o Phase: Oil water gas
Polymer and surfactant injection
o Component: Water oil surfactant alcohol o Phase: Agues oleic micro-emulsion
Compositional model
Chemical model
Modeling Concepts
1. Developing study objectives.
2. Develop or select an appropriate simulator.
3. Review, collect and estimate appropriate data.
4. Make preliminary runs to establish model parameters and limitations.
5. Match available history.
6. Predict performance under different operating scenarios.
7. Analyze results and prepare a report.
8. Plan additional work.
Reservoir Simulation Steps
Essential steps in a simulator are:
1. Read input data (include reservoir description)
2. Initialize
3. Start time-step calculations
• linearize equation,
• start iteration loop (Newtonian iterations),
• solve linear equations by direct or iterative methods,
• test for convergence, and
• repeat iterations if necessary.
4. Print and plot results at appropriate times
5. End if specified constraints are violated
6. Increment time and go to step 3 if end is not reached
7. End when run complete
Historical Developments
Evolution of reservoir engineering and reservoir simulation
is outlined in this section. The comments that follow are
divided into three categories:
• Traditional Reservoir Engineering (1930 -)
• Early Reservoir Simulation (1955 – 1970)
• Modern Reservoir Simulation (1970 onward)
•
Analogy
-
Well Productivity
- Recovery Factors
- Reservoir Dat
a
•
Experimental
-
measure the reservoir characteristics in
the laboratory models
- Scale these results to the entire
hydrocarbon accumulations
•
Mathematical
-
Basic conservation laws and
constitutive equations
- Material Balance (continuity equation)
- Equation of motion (momentum
equation)
- material balance+ decline curve+
statistical approaches+ analytical
methods(pressure-transient and
Buckley–Leverett methods)
Reservoir Models Used: History of
Simulation
Reservoir Simulator Classifications
They can be classified in different approaches based on:
1. Type of
reservoir fluids
being studied (include gas, black oil, and
compositional simulators) and the recovery processes being modeled (include
conventional recovery (black oil), miscible displacement, thermal recovery,
and chemical flood simulators).
2. The
number of dimensions
(1D, 2D, and 3D), the number of phases
(single-phase, two-(single-phase, and three-phase), and the coordinate system used in the
model (rectangular, cylindrical, and spherical).
3. Rock structure
or
response
(ordinary, dual porosity/permeability, and coupled
hydraulic/thermal fracturing and flow).
Why it is accepted???
The widespread acceptance of reservoir simulation can be attributed to
the advances in:
A.
computing facilities
B.
mathematical modeling
C.
numerical methods
D. solver techniques, and
E.
visualization tools
Eclipse Reservoir Simulator
• Commercial reservoir simulator for over 25 years
• Black-oil
• Compositional
• Thermal
• Streamline
Eclipse Reservoir Simulator
Local Grid Refinement Gas Lift Optimization Gas Field Operations Gas Calorific Value-Based
Control Geomechanics Coalbed Methane Networks Reservoir Coupling Flux Boundary Environmental Traces
Open-ECLIPSE Developer's Kit
