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Development of a 2-D Black Oil Reservoir Simulator with Unique Grid-Block System. Emeline Chong. July 7, 2004. Harold Vance Department of Petroleum Engineering. Presentation Outline. Motivation Problem Definition Objectives Approach Program Validation/Evaluation Conclusions.
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Development of a 2-D Black Oil Reservoir Simulator with Unique Grid-Block System Emeline Chong July 7, 2004 Harold Vance Department of Petroleum Engineering
Presentation Outline • Motivation • Problem Definition • Objectives • Approach • Program Validation/Evaluation • Conclusions
Motivation Diagonal Parallel Not to scale
GRID ORIENTATED PARALLEL TO INJECTOR-PRODUCER PAIRS (PARALLEL RUNS) GRID ORIENTATED AT 45 TO INJECTOR-PRODUCER PAIRS (DIAGONAL RUNS)
20 acres Mobility Ratios : M = 0.5 M = 1.0 M = 10.0 10 acres
Motivation Brand, Heinemann, and Aziz (1992) – “In general, Grid Orientation Effect cannot be overcome with grid refinement.” (SPE 21228)
Motivation Sammon (1991) Chen & Durlofsky (1991) Mattax & Dalton (1990) Wolcott et.al. (1996) Shiralkar (1990) Brand et.al. (1991) Ostebo & Kazemi (1992) Yanosik & McCracken (1979) Shiralkar & Stephenson (1987) Pruess & Bodvarsson (1983) Todd et.al. (1972)
Problem Definition Grid orientation effect significantly affects the results of immiscible displacements in reservoir simulation
Objectives • Developing a 2-D, 3-Phase reservoir simulator using finite difference formulation • Reducing the grid orientation effects in a grid model
Approach 2-D, 3-Phase IMPES finite difference simulator with unique grid model “Sim2D”
2D,3-Phase Cartesian Grid • Initial Condition • Rock/Fluid Properties Well Model Well Constraints HGB Grid IMPES Matrix Form Matrix Solver Pn+1, Son+1, Swn+1, Sgn+1 Cutback/Saturation Control Program Validation
IMPES MethodFinite Difference Equations • Oil • Water • Gas
IMPES Steps… • Calculate coefficients of the pressure equation • Calculate solution of the pressure equation implicitly (matrix equation) for: pn+1 • Calculate solution of the saturation equations explicitly for: Son+1, Swn+1, and Sgn+1
IMPES Method • 4 unknowns per block: pn+1, Son+1, Swn+1, and Sgn+1 • To find the unknowns, we need one more equation per block: Son+1 + Swn+1 + Sgn+1 = 1 • Assures fluid volumes fit the pore volume
IMPES Method • Oil • Water • Gas
IMPES Method Summing up all saturation equations:
IMPES Method Approximate Vpn+1 on the right hand side using the identity: and a chord slope:
IMPES Method Then, where, Likewise,
IMPES Method Final equation can now be written as:
I I J J N W E S Hybrid Grid Block (HGB) System NW NE SE SW
Grid Numbering Numbering #1 Example: 18 Grid Blocks
Grid Numbering Numbering #2 Example: 18 Grid Blocks
Grid Numbering Numbering #3 Example: 25 Grid Blocks
Well Model Peaceman Well Model (1983): Δm For square gridblock, where, α = mass species; oil/water ro = effective wellbore radius
Well Model for regular polygon (Palagi, 1992): j = neighbor of wellblock i bij = side of polygon dij = distance between gridpoints N = number of equal sides Well Model i
Cartesian Sim2D Cartesian Eclipse 100 HGB Sim2D Program Validation
Example Case: Two-Dimensional Areal Model Showing Primary Depletion of an Undersaturated Reservoir (One Producer Well, One Injector Well, Isotropic, 2-Phase, Oil/Water)
Application ofHGB grid system to Reduce Grid Orientation Error