Classification of Fractured Reservoirs - PowerPoint PPT Presentation

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Classification of Fractured Reservoirs

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  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 theessential storage capacity and permeability in a reservoir. The matrix has little porosity or permeability. Type II:Rock matrix provides the essential storage capacity andfractures 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. Decreasing Effect of Matrix Increasing Effect of Fractures Schematic Distribution of Fractured Reservoir Types All Fractures 100 % k f I II % of Total Permeability III M 100% k m IV % of Total Porosity 100% ff 100% f m All Matrix Nelson (1999)

  4. Evaluation Characteristics byFractured 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 byFractured 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 byFractured 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 byFractured Reservoir Type • Type 4 (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. 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 Inappropriate Floods & Non-Recognition Beaver Creek Hugoton 0% 100% Matrix All 0% %Porosity in Fractures R.A.Nelson, 1999