1. Classification of Fractured Reservoirs
Delineates the reservoir parameters most important in quantifying the reservoir (highgrades data acquisition)
Potential production & evaluation problems can be anticipated
The style of reservoir simulation necessary can be constrained

2. Fractured Reservoir Classification
Type I: Fractures provide the essential storage capacity and permeability in a reservoir. The matrix has little porosity or permeability.
Type II: Rock matrix provides the essential storage capacity and fractures provide the essential permeability in a reservoir. The rock matrix has low permeability, but may have low, moderate, or even high porosity.
Type III: Fractures provide a permeability assist in an already economically producible reservoir that has good matrix porosity and permeability.
Type IV: Fractures do not provide significant additional storage capacity or permeability in an already producible reservoir, but instead create anisotropy. (Barriers to Flow)
Nelson (1999)

3. Schematic Distribution of Fractured Reservoir Types
All
Fractures
100 % k f I II
Permeability
% of Total
III
Decreasing Effect of Matrix
Increasing Effect of Fractures M
100% k m IV
% of Total Porosity
100% f f
100% f m
All
Matrix
Nelson (1999)

4. Evaluation Characteristics by Fractured Reservoir Type
Type 1 (Fractures provide essential por. & perm.)
Fracture characteristics define reserves
Static description is critical
Production highly variable in 4-D
Few wells required to deplete

5. Evaluation Characteristics by Fractured Reservoir Type
Type 2 (Fractures provide essential perm.)
Cross flow and rate control are critical
Fractures define rate
Water influx must be monitored & intervention planned
If overpressured, fracture closure must be controlled

6. Evaluation Characteristics by Fractured Reservoir Type
Type 3 (Fractures provide a perm. assist)
Fractures define anisotropy
Highly customized flood patterns needed
Rates & drainage areas better than predicted from matrix alone

7. Evaluation Characteristics by Fractured Reservoir Type
Type (Fractures create perm. reduction)
Fractures create baffles, barriers and compartments (flow & saturation)
Fracture descriptions made generally by core only
Inefficient drainage & sweep
Rates & reserves lower than predicted from matrix alone

8. Reservoir Type 1 Fields

9. Contrasting History

10. Reservoir Type 2 Examples

11. Contrasting History

12. Reservoir Type 3 Examples

13. Contrasting History

14. Attributes of
Reservoir Types

15. %Permeability in Fractures
Critical Exploration & Development Issues by Fractured Reservoir Type
Pressure, Wellbore Stability & Rate control
All Fractures
100%
Development Patterns
& Well Paths
Blackburn
Valhall
West Rozel
Beaver River/
Pointed Mountain
Hod
Sabria/
El Franig
Sajaa/
Kahaif
Pearsall
Anschutz Ranch East, Low
Opon
Whitney Canyon
Middle Ground Shoals/
Granite Point
Lost Soldier
Madison
Reserve Calculation &
Rate Decline
Wamsutter
%Permeability in Fractures
Lost Soldier
Tensleep
Liuhua
Ryckman Creek
Darius
Anschutz Ranch East,High
Rijn
Cedar Rim
Pineview
Beaver Creek
Inappropriate
Floods & Non-Recognition
Hugoton 0%
100%
Matrix
All 0%
%Porosity in Fractures
R.A.Nelson, 1999