EOR Sim - MZA4

Reservoir Simulation for
Enhanced Oil Recovery Methods

Objective:
Detailed simulation of the EOR process for feasibility study
Mehdi Zallaghi
PUT Research Center – Tehran
Email: mmzallaghi@gmail.com
Fall 2017
EOR Methods Simulation
 Gas Injection Simulation

 Immiscible gas injection
 Miscible gas injection (MMP calculation methods)
 Chemical EOR Simulation
 ASP flooding Simulation
 Low Salinity Flooding
 Foam Flooding
 Solvents Simulation
 Thermal EOR Simulation
 Steam Injection Simulation (CSS)
 SAGD Simulation
 Hot Water Injection
 In-situ Combustion Simulation
Reservoir Simulation for Enhanced Oil Recovery by: Mehdi Zallaghi email: mmzallaghi@gmail.com
Enhanced Oil Recovery (EOR)
Planning EOR
 Reservoir characterization for EOR
 EOR Screening (e.g. thermal, chemical, miscible gas(CO2,N2,HC))
 Laboratory feasibilities (e.g. core flooding)
 Detailed simulation of the EOR process (feasibility study)
 Pilot Test (design, implementation and monitoring)
 Full field implementation (Integrated reservoir study for full field development plan (FDP)(
in Iran
Master development plan (MDP)

Other workflows?
EOR Project Timeline
EOR Process Geologic Design Field

Field Initial
Method Pilot Testing Implementati
Selection Selection Studies Parameters Response
Screening on
Field Scale
Core Scale • Hard to know where fluid is flowing
• Temperature gradients
• 1D flow
– Cold inj. water hot reservoir
• Constant temperature
Large variation in flooding rate
• Constant flooding rate
– High flooding rates close to injector and producer
• Molecular diffusion important
• Molecular diffusion?
• Usually matrix flow
• Fracture and matrix flow
• Dispersion
Gas Injection Simulation
Immiscible and Miscible
 Gas Injection Simulation

 Immiscible gas injection
 Miscible gas injection (MMP calculation methods)
Calculation of phase behavior in a reservoir model

• Using a "black-oil" approach based on simple interpolation of PVT properties as a function of pressure
• Using a "compositional" approach based on a thermodynamically-consistent model such as a cubic equation of state (EOS)
 When use a Black-Oil Model ?

 When is an EOS Model required?
Gas injection design
Miscible or Immiscible?
 Minimum miscibility pressure (MMP) is essential in gas flooding designs.
 MMP is the lowest pressure at which gas and oil become miscible at a fixed temperature.
 Immiscible gas injection generally used for reservoir pressure maintenance.
 Theoretically, the pore scale efficiency of miscible injection (or displacement efficiency) is 100% in the absence of dispersion
 During gas injection, miscibility can develop in one of two ways:

 First-contact miscibility (FCM)  single phase at any arbitrary ratio
 Multi-contact miscibility (MCM)  mass transfer of components between the two phases
 Multi-component miscibility displacements types:

 vaporizing gas drive,
 condensing gas drive
 condensing/vaporizing (CV) drive
Gas injection design
MMP estimation
 Experimental methods (slow and expensive)
 Slim-tube experiments  most widely accepted
 Mixing-cell experiments
 Vanishing interfacial tension experiments.
 Rising bubble/falling drop experiments
 Computational methods (fast and cheap)
 Simulation of slim-tube
 Analytical methods - (use the method of characteristics (MOC))
 Mixing cell (cell-to-cell)- (based on repeated contacts between gas and oil)
Assumption: phase behavior can be accurately described with a tuned EOS
Gas sources for injection

• Produced gas
• Deeper gas horizons
• Nearby gas fields
• Flue gas (88% N2, 12% CO2) or nitrogen(air)
• Natural and industrial CO2 source
Reservoir simulators
Classified in terms of representation of hydrocarbon fluids

Black oil simulator
 Two hydrocarbon components (gas and oil) plus water
 Tables where the fluid properties vary with pressure
 Oil Formation Volume Factor (FVF) Bo
 Gas FVF Bg
 Water FVF Bw
 Solution Gas-Oil Ratio (GOR) Rs
 Simulation of processes where the mass transport between the fluid phases is of minor importance
Compositional simulator
 Multicomponent
 Flash calculation using a cubic EOS
 Characterized oil
• Simulation of processes where compositional effects are of major importance
 Depletion of volatile/gas condensate reservoirs
 Injection of non-equilibrium gas for miscible or near-miscible displacement
Black-Oil Model
 Three fluid components: Gas, Oil, and Water
 No mass transfer between water and hydrocarbon phases
Black-oil PVT models

 For low- to medium-gas-oil-ratio (GOR) oils, a traditional differential liberation experiment (DLE) is used, with corrections for
separator flash to calculate oil formation volume factor (FVF) Bo and solution GOR Rs, as well as the gas FVF Bg.
 For highly volatile oils, the EOS method gives substantially different and improved black-oil properties compared with the traditional
laboratory DLE/separator-corrected approach.
Modified black oil (MBO)

 for gas condensate and volatile oil reservoirs
 Common and general approach to generating black-oil PVT properties uses an EOS model to simulate a depletion-type PVT experiment
Compositional Model
Compositional Model
– Significant mass-transfer between oil and gas phases
– Fluid properties are functions of pressure and composition
– Pressure, saturation and composition
 Transport mechanisms: Convection and Diffusion

 Material balance for each component
 For hydrocarbon components:
 For water
 EOS for components distribution between oil and gas phases
Compositional Simulation
 Methods compositional simulators to model the phase behavior:

 K-value methods can be used with a systematic method of modifying convergence pressures with compositions.
 Equation of state methods are also in common usage and have the advantage of predicting densities as well as the
molecular equilibrium.
PVT Prediction Methods

1) K-value, pk (convergence pressure) method.(This method is faster and can be matched with
lab data and EOS , but it needs correction for the density of oil and the density of gas)
2) Equation of State method (EOS).( It matches more accurate with the lab data and we can
get the density of oil and gas)
a) Peng-Robinson
b) Redlich-Kwong
Case Study
Steps:
- PVTi modeling (tuned cubic EOS)
- 1D slim-tube simulation(computational simulator
- Estimated MMP
 Several simulations with varying number of grid blocks are needed for a reliable MMP estimate.
Component MW %
CO2 28.01 0.001
N2 44.01 0.0028
C1 16.04 0.4861
C3 59.94 0.2174
C7+ 119.70 0.2098
CX 276.32 0.0829
PVT data provided in the Excel file

File address: EOR_Sim_Files/PVT/SilmtubePVT.pvo
Case Study
Slim-tube experiments
1-D slim-tube simulation
L: 10 meter
Unit: LAB
EoS: PR3
Components: 6
Grid dimensions: 200x1x1
Phases: OIL & GAS
Initialization: SOIL: 1 (XMF,YMF) SGAS: 0
INJECTOR in: 1
PRODUCER in: 200
Run for: 1.2 pore volumes injection
MMP: 2700 psi

Oil recovery at 1.2 pore volume of gas injected is
plotted versus pressure
File address: EOR_Sim_Files/PVT/Silmtube.data

Sector Model Simulation
Inverted five-spot
• No of Production wells: 4
• No of Injection wells: 1
• Porosity: 0.2
• Permeability: 10 mD
• Initial Pressure: 3350 psi
• Control mode: RATE
• Injection Rate: 5000 stb/day
• Production control: BHP 1500 psi
Data provided in “EOR_Sim_Files” folder: EOR_Sim_Files/GasInj/Sect_5spot.data

CEOR Methods Simulation
 Chemical EOR Simulation

 ASP flooding Simulation
 Low Salinity Flooding
 Foam Flooding
 Solvents Simulation
Black Oil or Compositional Simulator?

 Selection Criteria
 Guidelines for choosing
 Targets details
Data provided in “EOR_Sim_Files” folder: EOR_Sim_Files/CEOR/….

Chemical EOR Simulation
Chemical EOR  water-based EOR

• Typical oil recovery: 15 to 30% OOIP
Alkaline-Surfactant-Polymer (ASP) Injection • Cost: $2.50 to $8.00 per barrel
• Rate of return 40% or greater
Polymer
• high-molecular-weight and viscosity Types of Polymer
• added to the water
Xanthan  Biopolymer/ polysaccharide
• decrease the mobility of injected water
PAM& HPAM Synthetic (Polyacrylamide & partially hydrolysed)
• improve the sweep efficiency
Surfactant
 Surface-active agent
 Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.
Surfactants types based on the charge of the molecule head:
• Anionic (negative charge)
• Cationic (positive charge)
• Nonionic (no charge)
• Zwitterionic (positive and negative charge)

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Reservoir Simulation for

Enhanced Oil Recovery Methods

 Gas Injection Simulation

Master development plan (MDP)

EOR Process Geologic Design Field

 Gas Injection Simulation

Calculation of phase behavior in a reservoir model

 When use a Black-Oil Model ?

 During gas injection, miscibility can develop in one of two ways:

 Multi-component miscibility displacements types:

Gas sources for injection

Classified in terms of representation of hydrocarbon fluids

Black-oil PVT models

Modified black oil (MBO)

 Transport mechanisms: Convection and Diffusion

 Methods compositional simulators to model the phase behavior:

PVT Prediction Methods

C7+ 119.70 0.2098

PVT data provided in the Excel file

MMP: 2700 psi

File address: EOR_Sim_Files/PVT/Silmtube.data

Data provided in “EOR_Sim_Files” folder: EOR_Sim_Files/GasInj/Sect_5spot.data

 Chemical EOR Simulation

Black Oil or Compositional Simulator?

Data provided in “EOR_Sim_Files” folder: EOR_Sim_Files/CEOR/….

Chemical EOR  water-based EOR

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