3 & 4 Flashcards
Volumetric analysis use _____ to determine the volume in a process. Often use by Geoscientist
static information
Material balance and reservoir simulation use _____ to obtain estimates of fluid volumes originally in place in the reservoir.
dynamic data/information
What are the three decline curves?
• Exponential Decline curve
• Hyperbolic Decline curve
• Harmonic Decline curve
The production term “q” only exist for cells with wells (either production or injection). Only they differ in _____
sign(+,—)
If we maintain separate phase equations, we have _____ formulation with three equations per cell
FULLY IMPLICIT
the saturation derivatives with respect to time cannot be eliminated and _____
must be approximated using finite difference
where the pressures associated with the left- hand side of the equation are locationally-dependent on those on the right-hand side are time-dependent; however the pressures on the left-hand side require that some time level be assigned to them.
Explicit Pressure Solution
What IMPES means
Implicit Pressure, Explicit Saturation
Assuming saturation does not change _____ are held constant during pressure solution.
dependent quantities of relative permeability and capillary pressure
Since saturation-related variables are fixed, all we need to do is _____ .(Which is done by iteration process)
estimate the pressure-dependent variables
Simple Schematic of IMPES Procedure
- Guess pressures
- Calculate PVT properties (for Flow Coefficients)
- Calculate New Pressures
- Do New Pressures = Guessed Pressures?
No — Go back to step 1 but skip step 2 (inner iteration)
No — Go back to step 1 (outer iteration)
Yes — Go on. - Calculate Saturations
- Go to the next timestep and start step 1 again
Simple Schematic of Fully Implicit
Procedure
- Guess pressures and saturations
- calculate pvt properties, Pe and krcl (for flow Coefficients)
- Calculate New pressures and saturations
- Do New pressures = Guessed pressures and New saturations = Guessed saturations?
No — Go back to step 1 but skip step 2 (inner iteration)
No — Go back to step 1 (outer iteration
Yes — Go on - Go to the next timestep and start step 1 again
A variation in IMPES:
• Sequential Modification
• Fully implicit
Combines IMPES approach with Buckley Leverett Saturation Solution.
Sequential Modification
Is usually applied when there is large saturation changes over a given timestep. (extremely tiny timesteps are required)
Fully implicit
TWO TYPES OF MATRIX SOLUTION:
- Direct
- Iterative
Solves system of equations in one set of calculations
Direct
use some sort of predictor-corrector technique to converge on the answer.
iterative
SOLUTION TECHNIQUES
Sample Techniques: (Direct)
Gaussian Elimination (GAUS)
SOLUTION TECHNIQUES
Sample Techniques: (Iterative)
—Strongly Implicit Procedure (SIP)
—Successive Over-Relaxation methods (SOR)
—Conjugate Gradient-Like methods (CGL)
—Alternating Direction Implicit procedure (ADI)
