force workshop – 21 st nov. 2006 introduction to cmg cmg’s stars simulator the sagd process ...
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FORCE Workshop – 21st Nov. 2006FORCE Workshop – 21st Nov. 2006
Introduction to CMG CMG’s STARS simulator The SAGD Process GEOMECH and its features Discussion on iterative coupling
CMG’s porosity function Examples Future Work
Long History in SimulationLong History in Simulation
Based in Calgary Canada 28 years of simulator development Mainly in IOR and thermal methods Over 70 staff
Established as research foundation
Fiscal
1978
Fiscal
1997
Fiscal
1998
Fiscal
1999
Fiscal
2000
Fiscal
2001
Fiscal
…
Fiscal
2005
Became a public company CMG:TSX
CMG’s Offices CMG’s Offices
Over 270 Customers in 44 Countries
Houston, Texas
London, England
Head OfficeCalgary, Canada
Calgary, Alberta
Caracas, Venezuela
Beijing, China
Moscow, Russia
STARS –SimulatorSTARS –Simulator
Market Leader in Advanced Process Simulation STARS simulator
Thermal (CS, SAGD, ES-SAGD, and Air Injection)
Electrical Chemical (ASP, Foams, Gels, Microbial)
Compositional (CO2, N2, VAPEX, Gas Injection)
Geomechanical (Finite Element)
Over 1,400 licenses in use worldwide mainly for thermal and IOR process modelling work Particularly steam processes e.g. SAGD
SAGD ProcessSAGD Process
Game changer for the Canadian oil industry $80 billion investment over the
next 10 years Shallow 150-400m; poorly
consolidated; immovable liquid
BlackRock Ventures Hilda Lake $260,000,000
CNRL Horizon Ph I $8,000,000,000
ConocoPhillips/TFE/Devon Surmont $1,000,000,000
Deer Creek/Enerplus Joslyn Creek Phase 2 $500,000,000
Devon Jackfish $400,000,000
Devon Dover Pilot $30,000,000
EnCana Foster Creek $290,000,000
Husky Tucker Lake $350,000,000
Imperial Current Cold Lake ~ $7,000,000,000
Imperial Mahkeses $650,000,000
Imperial Nabiye, Mahihkan $1,000,000,000
Japan Canada Hangingstone main $250,000,000
Nexen/OPTI Long Lake $2,500,000,000
Suncor Firebag Phase 1 $600,000,000
Investment Total $22,830,000,000
SAGD ProcessSAGD Process
Geomechanics plays an important part from both a reservoir and surface expression perspective! Surface heave of up to 20cm has been reported (Wang and Kry,
1997) for cyclic steaming in the Canadian formations At Peace River, Shell uses surface tilt meters to monitor the
process Large stress changes associated with the process
Isotropic Unloading – pore pressure increase under high pressure steam injection
Shear Failure – thermal stresses at steam chamber boundary caused by the large thermal gradient normal to the front surface Typically 250C over a few metres!
SAGD – Example (T and uvert)SAGD – Example (T and uvert)
SAGD ProcessSAGD Process
Isotropic unloading will increase and k Although if temperature dominates these terms can actually
decrease! However, the thermally induced shearing process can significantly
increase permeability Up to 6 times vertically and 2.5 times horizontally (Li and
Chalaturnyk, 2004) Dependent on stress path, but shallow SAGD operations benefit
most from having low confining stress Major contributor to injectivity and overall enhancement of
production rates Stress state cannot be modelled by simple flow simulator table
look up approaches (pore pressure vs poro or perm multiplier) So it is important to be able to model the stress alterations and get
the geomechanical effect right, in order to understand fully the injection and production response of your SAGD system
SAGD SummarySAGD Summary
Huge investment in the SAGD process Geomechanical effects can have a strong effect on
the production and injection response of the system Surface expression also significant
Simple poro/perm tables do not capture the full geomechanical effect
Stress path is important to quantify the effect and magnitude of the reservoir alterations
So how does CMG deal with this situation?
Geomechanics Module (GEOMECH)Geomechanics Module (GEOMECH)
Calculation SpeedCalculation Speed
In the SAGD situation we know that geomechanics plays an important role, but can we afford to model it?
It is the calculation time that has typically determined whether it is worthwhile modelling geomechanics, and to what extent. Fluid flow typically requires the solution of 4 eqns per block Full 3D Geomechanics can require up to 24 eqns per block! So, GEOMECH solution can take up to 85% of the cpu time!
The memory requirement also increases similarly 150,000 cell; inverted nine spot steam flood; 529 wells
No geomech - 450Mb 2D geomech – 820Mb 3D geomech – 3760Mb
Calculation Speed - ExampleCalculation Speed - Example
Surmont, SAGD, 9 well pair (half pad) 1,722,780 Grid cells 6.5 year forecast Serial runtime on IBM 1.65GHz P5
32 days!
Add 3D geomechanics 200+ days expected with 40-50GB RAM!
Reservoir and Geomechanics GridsReservoir and Geomechanics Grids
Reservoir Flow Corner-point grids
Geomechanics Quadrilateral 8-node finite elements that match initial
corner-point grids 8 nodes initially co-incident with grid corners 2D Plain strain or full 3D Elements
Finite elements model deformations whereas corner-point grids remain the same during the simulation
The finite element deformation is converted into a change in porosity in corner-point grids As reservoir flow grid bulk volume is invariant
CouplingCoupling
Fully Coupled Primary unknowns – (P, T and u) Pressure; Temperature and
Displacement solved simultaneously The ultimate solution, but very computationally expensive
Explicit Coupled Flow information sent to GEOMECH module but results not fed
back to the flow module ie Flow is unaffected by GEOMECH Iterative Coupled
P and T solved first and then u i.e. the GEOMECH calculations are calculated one step behind the flow calculations
Information is passed between flow and GEOMECH modules Flexible, as the 2 modules can be coded independently, and
quick This coupling uses a modified porosity * for feedback to the
flow simulator
Basic Flow EquationsBasic Flow Equations
Conservation of fluid in a deformable porous medium
b
p
V
V
volumebulkCurrent
volumeporeCurrentporosityTrue
0b
p*
V
V
volumebulkInitial
volumeporeCurrentporosityservoirRe
v* 1
0Qgpk
t ffff*
0gk
1
fffvf Qpt
Basic Geomechanics EquationsBasic Geomechanics Equations
p : pore pressure
σ' : effective stress
σ : total stress
α : Biot’s number
σ = σ' + αp
gTEpdz
d
dz
duE
dz
dr
Coupling Deformation-Pressure-Temperature Equation (1D):
Basic Equation SummaryBasic Equation Summary
Equation for Fluid Flow
Equation for Heat flow
Equation for Deformable Medium
Described in Tran, Nghiem, and Buchanan (SPE 97879)
0g*
ffff Qpt
k
gTp rT
IuuC
2
1:
0)(g)1( **
hfffrrff QTHpUUt
k
Equation CommunicationEquation Communication
From Reservoir Flow to GEOMECH P and T appears in GEOMECH calculation
Feedback from GEOMECH to Reservoir Flow Porosity Function
* = f (P,T,v) or f (P,T,m)
Porosity Function *Porosity Function *
Tran, Settari and Nghiem (2004)
nnnnnnnn TTCppC 11
10**
1
E: Young's moduluscb: Bulk compressibilitycr: Solid rock compressibility: Thermal expansion coefficient: Poisson's ratio: Biot numberm: Mean total stressn: Time level nn+1: Time level n+1
n120
0n accC
n2211n accC
Iterative Two-way CouplingIterative Two-way Coupling
NO
YES
NO
n = 0
Convergence
Solving p, T , *, k
n = n + 1 Solving u, and σ
Convergence
Newtonian Iterations
Coupling Iterations
Updating * coefficients
Porosity FunctionPorosity Function
Crux of the iterative coupling method Approximation of actual geomechanics behavior Converts geomechanics behavior to a form that could be used
by a reservoir simulator Compressibility and Thermal Expansion Coefficients
Discrepancies can exist between simulator porosity and geomechanics porosity but a threshold forms part of the final coupling iteration convergence check For difficult problems (e.g. plastic deformation and shear failure),
large differences may exist between the 2 porosities and many coupling iterations may be necessary E.g. Dean’s problem # 3 requires 5 iterations (SPE 79709)
CMG’s porosity function formulation aims to reduce the total number of coupling iterations to as low a value as possible E.g. Dean’s problem # 1,2, and 4 required 1 iteration
Porosity Function ImprovementsPorosity Function Improvements
Tran, Settari and Nghiem (SPE 88989, 2004)
Tran, Nghiem and Buchanan (SPE 93244, 2005)
Further improvements Provide good match between GEOMECH and
reservoir simulator porosity
n1n1nn1n
0n
*n
*1n TTCppC
n1n1
1nn1n0
1n*n
*1n TTBppB
VPOROSGEO 14,1,1 SAGD3_GEOM_COUPLING_MOHR.irf
Time (Date)
Po
rosity - G
eo-C
orrected
: VP
OR
OS
GE
O 14,1,1
2000-4 2000-7 2000-10 2001-1 2001-4 2001-7 2001-10 2002-1
0.2998
0.3008
0.3018
0.3028
Porosity - Geo-Corrected: VPOROSGEO 14,1,1 Porosity - Geo-Corrected: VPOROSGEO 15,1,19 Porosity - Geo-Corrected: VPOROSGEO Average Void Porosity: VPOROS 14,1,1 Void Porosity: VPOROS 15,1,19 Void Porosity: VPOROS Average
Porosity ComparisonPorosity Comparison
PermeabilityPermeability
What about permeability? Most flow simulators use a simple vs k look up table
Permeability Function k = k (*) basic look up provided
Additionally ln(k/ko) = C v (Li and Chalaturnyk, 2004)
C is a matching parameter from lab measurements Table lookup (allows for anisotropy)
Ki/Koi (i=x,y,z) versus Mean effective stress Mean total stress Volumetric strain
Fractured Model PermeabilityFractured Model Permeability
GEOMECH Highlights - FeaturesGEOMECH Highlights - Features
Current Iterative two-way coupling and one-way coupling Geomechanics for Dual Porosity/Permeability Stress-dependent permeability Temperature-dependent geomechanics properties
Future (near current!) Improved constitutive models for SAGD operations
Generalised Plasticity Drucker Prager and Matsouka-Nakai augmented by Plastic Potential function; Friction Hardening; Cohesion
softening; and dilation angle based on Rowe’s dilatancy theory
GEOMECH Highlights - SpeedGEOMECH Highlights - Speed
Current Improved porosity function
Advantages of a fully coupled system without the associated cost Geomechanics grid larger, or smaller, than reservoir grid Control of the frequency for calling GEOMECH AIM and PARASOL
Future Generalised grid mapping
GEOMECH and flow grids can be dissimilar Less GEOMECH cells
Allow CMG’s Dynagrid functionality Further flow grid speed enhancement
Apply PARASOL to the GEOMECH calculations
Calculation Speed - ExampleCalculation Speed - Example
Surmont, SAGD, 9 well pair (half pad) Serial runtime on IBM 1.65GHz P5
32 days!
Add 3D geomechanics 200+ days expected with 40-50GB RAM!
Parallel (8cpu) + Dynagrid Currently: 32 days < 2 days Future: Add full 3D geomechanics 200+ days ???? ~4 days expected!
Leading the Way inLeading the Way in Reservoir SimulationReservoir Simulation