CHEMICAL AND PETROLEUM ENGINEEG DEPARTMENT

UNIVERSITY OF CALGARY

 NATURALLY FRACTURED RESERVOIRS SYLLABUS (ENCH 649)

 

Geologic Aspects 
 
Definitions. Paleo stresses and in-situ stresses. Mechanical behavior of rock.
Reasons for generation of fractures. Tectonic, regional, contractional  and surface related fractures.
Storage capacity of matrix and fractures. Classification.
Migration and accumulation of hydrocarbons in fractured reservoirs.
Sources of information:
     Direct:        Core analysis, drill cuttings, downhole cameras
     Indirect:      Log analysis, well testing, inflatable packers and production history
Radius of curvature.
Mapping of fracture trends.
Link to Unconventional Reservoirs.
 
Petrophysics
 
Comparison of dual porosity models.
Use of triple porosity model.
Cross-plotting techniques.
Porosity exponent, m, in naturally fractured reservoirs.
Water saturation exponent, n, in naturally fractured reservoirs.
Water saturation in matrix, fractures and the composite system.
P1/2 statistical analysis for calculating water saturation.
Total, matrix, and fracture porosity.
Fracture Completion Log.
The uncertainty of calculating hydrocarbons-in-place.
Use of conventional and specialized well logs for evaluation of naturally fractured reservoirs.
Link to Unconventional Reservoirs.

Well Testing

Conventional reservoirs interpretation
Naturally fractured reservoirs interpretation
     Parameters lambda and omega
     Fracture permeability and fracture-matrix average permeability
     Fracture and total porosity
Size of matrix blocks, effect of matrix block shape (Tectonic, regional and contractional fractures) and effect of partial secondary mineralization on pressure data
Skin due to formation damage and pseudo-skin due to partial secondary mineralization within natural fractures
Radius of investigation equation for fractured reservoirs
Variable-rate buildup and drawdown
Effect of a single seating fault and faults intersecting at any angle on pressure data (fault-related natural fractures)
Bounded reservoirs
Horizontal wells, effect of x, y, z anisotropy
Type Curves
     Uniform flux vertical fractures
     Infinite conductivity vertical fractures
     Finite conductivity vertical fractures
     Horizontal fractures
     Effective reservoir permeability and fracture half-length
     Dual porosity systems without and with hydraulic fractures.
     Dual porosity systems: Outer boundaries with or without pressure maintenance
     Dual porosity systems: Pressure Interference in isotropic and anisotropic reservoirs
Gas Wells
Link to Unconventional Reservoirs.

Completion Methods

Open hole
Perforated completions
Advantages and disadvantages
Hydraulic fracturing and acidizing
Link to Unconventional Reservoirs.

Tight Gas, Shale Gas, Tight Oil, Shale Oil, CBM

Log interpretation Principles
Performance forecast Principles
These unconventional reservoirs are linked to naturally fractured reservoirs throughout the course.

Horizontal Wells

Advantages and Disadvantages
Use and misuse
Improvements in productivity
Link to unconventional reservoirs.

Primary Recovery

Saturated and undersaturated reservoirs
Fracture and effective system compressibility
Relative permeability for fractures, matrix and composite system
Material balance
  Gas-oil ratio and oil saturation equations
  for depletion and gas cap-drive reservoirs
  Water-drive reservoirs
  Recovery as a function of pressure and time
  Well spacing
Water and gas coning through fractures
Production decline type curves
Horizontal wells
Link to unconventional reservoirs.

Secondary Recovery

Gas Injection
Material balance, gas-oil ratio and oil saturation equations for depletion and gas
cap drive reservoirs with dispersed gas injection
Recovery as a function of pressure and time
Well Spacing
Water Injection
  
   Areal sweep efficiency
      Importance of fracture orientation
Co-current and counter-current imbibition displacement
Water Influx from conventional unfractured aquifers
Water influx from naturally fractured aquifers
Link to unconventional reservoirs.

Case Histories

Special features of naturally fractured reservoirs in sandstones, 
carbonates, shales, chert, and basement rock
Micro-simulation of naturally fractured cores
Simulation of naturally fractured reservoirs
Undiscovered naturally fractured reservoirs, why and how?
Link to unconventional reservoirs.
 
Economic Considerations for Naturally fracture Reservoirs
 
Link to unconventional reservoirs.