1. 2010 SPWLA Topical Conference
Integration of
Reservoir Rock Types
in Simulation Models
Shawket Ghedan, PhD
Petroleum Institute
Feb 10
Integration of RRTs in Sim Models

2. Integration of RRTs in Sim Models
Development and Identification of RRTs
Reservoir Rock Types, RTTs developed by integrating:
Petrophysical Lab data,
Pore system information, and
Capillary Pressure Data.
RRTs can be identified by the following parameters:
Rock Fabric: texture, grain size, packing & pore geometry
Proportion of primary porosity and secondary porosity.
Porosity/ permeability relationships
Range of, and similarity in pore throat size distribution,
Similar Pc curves and saturation end points.
Feb 10
Integration of RRTs in Sim Models

3. Integration of RRTs in Sim Models
RRTs in Static and Dynamic Models
Static RRTs are routinely employed for:
Modeling of reservoir petrophysical attributes, as well as
Building & assigning the required water/ oil and Gas/ oil Kr curves to the different cells of the simulation models.
There is a problem with the second application:
Static RRT schemes do not consider the reservoir multiphase flow properties of wettability, fluids IT, etc…
Feb 10
Integration of RRTs in Sim Models

4. Integration of RRTs in Sim Models
Static vs Kr-Defined RRTs
Hamon introduced the Kr-defined rock types (SPE 84035, 2003 ATCE).
Definition of Kr-Defined Rock Types:
Kr-defined rock types are defined as units of rock characterized by similar ranges of pore geometry and wettability indicators resulting in a unique relative permeability saturation relationships.
Feb 10
Integration of RRTs in Sim Models

5. Integration of RRTs in Sim Models
Kr-Defined RRTs or Dynamic RRTs
For the same saturation history cycle in a reservoir, the rock multiphase flow properties would only be a function of wettability only for any static RRT.
In a reservoir with a wettability profile, each RRT would have many Wettability Driven Dynamic RRTs.
Therefore, imposing the effect of reservoir wettability on the RRTs is essential in developing and assigning the Kr curves to the cells of simulation models.
Each would have unique relative permeability curves and saturation endpoints.
Feb 10
Integration of RRTs in Sim Models

6. USBM WI vs Depth from Well A of Hawiyah area
SPE
SPE
Feb 10
Integration of RRTs in Sim Models

7. USBM WI versus Depth from Well B of Hawiyah area
SPE
SPE
Feb 10
Integration of RRTs in Sim Models

8. USBM WI versus Depth for Uthmaniyah area
SPE
Feb 10
Integration of RRTs in Sim Models

9. Reservoir Wettability Profile
Wells perforations
Producers down to X000 ftss Injectors up to X150 ftss
Wettability Oil Wet at Top structure Water Wet Below DOL.
Feb 10
Integration of RRTs in Sim Models

10. Integration of RRTs in Sim Models
Transition Zone?
Transition zones in Carbonate reservoirs could be fairly thick. depending on reservoir characteristics.
Transition zone is conventionally defined as that part of the reservoir where water saturation start to deviate from irreducible saturation down to 100% saturation.
Feb 10
Integration of RRTs in Sim Models

11. Integration of RRTs in Sim Models
Dry Oil Limit
300 oil producers, screened to identify
Deepest perforations of dry oil producers, and
Static RRTs of their producing layers.
From Which Identified the Dry Oil Limit of the reservoir RRTs.
Feb 10
Integration of RRTs in Sim Models

12. Integration of RRTs in Sim Models
Alternative Definition of TZ
DOL for any rock type was found to be always appreciably deeper than the top of the conventional transition zone.
The difference depends on the rock types encountered and profile of rock wettability changes.
Transition zone is better defined as the reservoir part where both phases of oil and water are mobile.
Feb 10
Integration of RRTs in Sim Models

13. Requirements of Saturation Tables
Log-derived W/O Pc curves.
Swirr at top of structure, Swc at Dry Oil Limit
Feb 10
Integration of RRTs in Sim Models

14. History Matching of Available Exp Kr Data
Use Corey Model for history matching
For various RTs determined No and Nw with Depth
Feb 10
Integration of RRTs in Sim Models

15. History matching of Available Exp Data
Exp Kr data for RT1
No and Nw variation with Depth
Feb 10
Integration of RRTs in Sim Models

16. History Matching of Exp Data
Poor Limestone RT8
No and Nw variation with Depth
Feb 10
Integration of RRTs in Sim Models

17. Variation of Corey Exponents
Poorer RTs Increasing Depth Porosity No Increase Decrease Constant Nw Increase Increase Constant
No = (2.8 to 5.0)
Nw = (1.3 to 2.6)
Feb 10
Integration of RRTs in Sim Models

18. Correlation of Sorw vs. Swi or Swc
Feb 10
Integration of RRTs in Sim Models

19. Correlation of Sorw vs. Swi or Swc
A correlation is developed to relate Sorw to Swc.
For Each Rock Type Swc ranges:
From Swirr, at the top of the reservoir, to
Sw value at the DOL level (top of the transition zones)
Feb 10
Integration of RRTs in Sim Models

20. Effect of Wettability on Krwmax and Sorw
It is well established that Sorw as well as Krwmax at Sorw would be lower for more water wet rock.
From Dave Bowen of Core Lab
Feb 10
Integration of RRTs in Sim Models

21. Impact of Wettability on End Points of Kr Curves
From Dave Bowen of Core Lab
From Dave Bowen of Core Lab
Feb 10
Integration of RRTs in Sim Models

22. Integration of RRTs in Sim Models
Krwmax versus Sorw
The available data did not yield clear relationship between Krw(Sorw) Vs Sorw
But a straight line relationship was forced that fits the general trend of the data.
Feb 10
Integration of RRTs in Sim Models

23. Number of DRRTs Per Static RRT
The number of DRRTs generated per each SRRT is decided by the number of the Sw increment employed to go from Swirr down to Swc at the DOL of each drainage Pc curve of each static RRT.
For instance, using a 5% Sw increment with seven maximum steps would produce up to 21 DRRTs (Kr sets) for each static RRT.
Feb 10
Integration of RRTs in Sim Models

24. Generation of DRRTs (Kr Curves)
1. For each depth, Swc is picked from any drainage Pc curve, ranging from Swirr up to Swc at DOL, then:
2. Use Swc to determine Sorw from the proposed correlations, similar to Land correlation
3. Use depth and rock type to determine Corey’s exponents, Nw and No, using a table look up.
4. Use Sorw to determine Krwmax from the proposed correlation (Kromax is taken as 1.0):
Feb 10
Integration of RRTs in Sim Models

25. Generation of Kr Curves
5. Use the Corey Krw and Kro models to determine Krw and Kro for any water saturation between any Swc and its Sorw.
Feb 10
Integration of RRTs in Sim Models

26. Generation of Kr Curves
Set of Kr curves for Limestone RRT 4 of 15% porosity.
Feb 10
Integration of RRTs in Sim Models

27. 2010 SPWLA Topical Conference?
Feb 10
Integration of RRTs in Sim Models