Transcript
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RESERVOIR SIMULATION
The will discuss all of the important facets of the reservoir modeling process.
Important factors that can dramatically impact the model results are emphasized.Specific topics include Data Acquisition, Fluid Properties, Rock-Fluid Interaction,
Grid Construction, History Matching and Prediction Cases.
These and other topics will help the attendees better understand how to plan and
conduct a reservoir simulation study and how to review a study conducted by
someone else.
Although there will be no direct computer related activities, time throughout the
two-days is reserved for discussion of case studies that were previously models
conducted by the teacher.
Attendees are also encouraged to bring materials and data (non-confidential)
relating to a potential project that they may be involved with in the future; and as
time permits, the class as a group (or groups, guided by the teacher) will brainstorm
and discuss the approach to be taken to achieve the desired study objectives.
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Why We Do Reservoir Simulation
Typical Problems
How many wells
What rate
Infill Drilling Perforation
Work-over
Pressure Maintenance
Water or Gas Injection
Pattern Flood
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Reservoir Drive Mechanisms1. Rock and fluid expansion2. Solution-gas drive
3. Gas-cap drive4. Water drive5. Gravity-drainage drive
6. Combination drive
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Solution Gas DriveLiberation, expansion of solution gas.
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Solution Gas Drive (Cont.)Typical Production Characteristics
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Solution Gas Drive (Cont.)
Reservoir pressure trend
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Gas Cap Drive
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Expansion of the original reservoir free gas.
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Gas Cap Drive (Cont.)Typical Production Characteristics
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Water Drive
Influx of aquifer waterTypes :
Edge-Water Bottom-Water
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Water Drive (Cont.)Typical Production Characteristics
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Gravity DrainageGravitational forces and reservoir fluids density difference.
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Combination Drive
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Average Recovery Factors
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SIMULATION:
"To Give the Appearance Of
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Reservoir Simulation
106-108 cells
Engineering/Simulation
Model
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Outlines
Brief of simulation
Introduction of Eclipse
Eclipse demo
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Brief of simulation
What is simulation?
What would be simulated usually?
Imitation or representation, as of a potential situation or in
experimental testing
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What is Reservoir?
Trapped HC, same pressure gradient
Tops
Layer
zone
Faults
Boundary
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What we shall know from a well?
Lithology (reservoir rock?)
Resistivity (HC,water,both?)
Porosity (how much HC?)
What type of HC
Formation mech. properties
Permeability / cap pressure
Shape of the structure
Geological information
Geothermal
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Formation
Tops
Layer
Zone
Dz (Thickness)
Dznet (Net Thickness)
Faults
Boundary
Permeability
Porosity
Fluid Property
Relative permeability
Saturation
Density, Gravity (API)
Viscosity
Formation Volume factor
Compressibility
How to describe reservoir?
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The reservoir is divided into a number of cells
Basic data is provided for each cell
Wells are positioned within the cells
The required well production rates are specified as a function of time
The equations are solved to give the pressure and saturations for each block
as well as the production of each phase from each well
Reservoir Simulation Basics
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Reservoir Simulation (1)
9 16
4 10 1 7 23
1 5 11 18 24 27
2 6 12 19 25 26
3 7 13 20 26
8 14 21
15 22
Numerical model of reservoir made up of an
array of cells. Equations are solved to calculate
pressures and flows.
Fluid flow - underlying concepts Conservation of mass
Darcys law
PVT model
Partial differential equations are written infinite-difference form and solved numerically
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WHAT BENEFITS ?
Golden Rule:
You can only produce once
You can simulate many times
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Overview of Modeling Procedure
History
match
Describereservoir
reservoir structure(seismic,logs)
gross and net thickness(logs)
well location and perforatd intervals
Design
reservoir grid
porosity, permeability(logs, cores)
fluid analyses(lab data)
pressure and contacts(logs, well tests, etc.)
Select simulator
model
black oil or compositional
fractured, condensate,etc
horizontal wells, EOR, thermal, etc.
Solve for
pressures and
saturations historical production data
Predict and
optmize future
production
investigate different scenarios
visualize results
economic calculations
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WINPROP PVT-Analysis & Simulation
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PVTi
Simulating
Experiments
Match
Creating
a Fluid System
Fitting
an Equation of State
FVF
Viscosity
EOS PVT Analysis & Simulation
Reseroir Simulation Grid
Export
Single Point
Pressure Depletion
Separator
Injection Study
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Schedule
Defines simulation wells, connections, vertical performance,artificial lift, controls and limits.
Defines groups, controls and limits.
Defines networks, compressors, etc. Specifies time dependent data.
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Wells- Path
-Tubulars
- Chokes
- Completions
- Workovers
- Production
- Injection
OCS
GGS
CTF
OCS
Network
Groups
-Capacities
-Demands
Simulation GridCell Properties Geological Model
Schematic of Data Handling in Schedule
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Numerical Grid
The reservoir was sub-divided into a 10x10x4 grid.
The numerical layers correspond to the geological
layers.
The x-y dimension of the grid blocks is 500 m by500 m.
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3-D Structure of Reservoir
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Structure and Geology
Layer
Number
Porosity Horiz. Perm
(mD)
Thickness
(m)
1 0.35 1000 5
2 0.3 5 10
3 0.25 300 15
4 0.2 100 30
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Layer 2 has numerous shale components.
The geologists best guess of the average
permeability of the mix of sand and shale is 5 Md.
The average Kv/K h ratio is 0.1. The top of the structure is approximately 2989 m
SSL.
The lowers edge of the reservoir in the aquifer is
approximately 3090 m SSL.
Structure and Geology
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Aquifer
There is a aquifer attached to the edge of thereservoir that provides an edge water drive.
The geologist has estimated that the aquifer has a
volume of approximately 9 x 108 Sm3 of water and
the aquifer productivity index is approximately 500
sm3/day/bar.
A analytical Fetkovich aquifer has be used to
represent the aquifer.
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PVT Data, Fluid Contacts, and Initial Fluids
in Place
A PVT description has been generated with the
Eclipse PVT program.
A live oil and dead gas system has been defined.
The bubble point pressure was determined as331.65 barsa.
The Rs at the bubble point was 477.91 sm3/sm3 ,
and the Rs at a depth of 4000 m SSL was
measured to be 486.60 sm3/sm3.
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The datum depth is the GOC = 3000 m SSL where
the initial reservoir pressure is 331.65 barsa.
The water-oil contact was measured to be 3085 m
SSL.A small gas cap exists at the top of the structure.
PVT Data, Fluid Contacts, and Initial Fluids
in Place
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The reservoir has a
Pore Volume of 360.8 x106 Rm3
Initial Oil In Place of 51 x106 Sm3Initial Water in Place of 173.6 x106 Sm3
Initial Free Gas in Place of 77.56 x106 Sm3
Initial Solution Gas in place of 24.4 x109 Sm3
PVT Data, Fluid Contacts, and Initial Fluids
in Place
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July 03 7
x-y View of 4 Layers with Initial Water Saturations
Layer 1
Layer 2
Layer 3
Layer 4
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x-z Cross-section with Initial Gas Saturations
July 03 8
x-z Cross-section with Initial Water Saturations
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Relative Permeability and Capillary
Pressure
The relative permeability and capillary pressure
were measured in the laboratory and are plotted in
attached slides.
The connate water saturation is 0.22. The critical/residual oil saturation in water is 0.35.
The critical oil saturation in gas with connate water
is 0.2.
The critical gas saturation is 0.04.
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Wells, Completions, Injection and
Production Rates
Two production wells were drilled at locations 8,5
(called P85) and 3,5 (called P35)
Both completed in layers 2 and 3.
The producers operate, during the history, at aconstant oil production rate of 1300 Sm3/day.
A water injection well and gas injection well were
also drilled.
The water injection well was shut during the history.
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The gas injection well called INJG was located in
position 5,5 and completed in layer 1 in the gas cap.
The gas injector re-injects 1,000,000 Sm3/day of
the produced gas. This was designed to help maintain the reservoir
pressure.
Wells, Completions, Injection and
Production Rates
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