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 historyRadius 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 dataSkin 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 WellsLink to Unconventional Reservoirs.
Completion Methods
Open hole Perforated completions Advantages and disadvantages Hydraulic fracturing and acidizingLink to Unconventional Reservoirs.
Tight Gas, Shale Gas, Tight Oil, Shale Oil, CBM
Log interpretation PrinciplesPerformance forecast PrinciplesThese unconventional reservoirs are linked to naturally fractured reservoirs throughout the course.
Horizontal Wells
Advantages and DisadvantagesUse and misuse Improvements in productivityLink to unconventional reservoirs.
Primary Recovery
Saturated and undersaturated reservoirs Fracture and effective system compressibilityRelative permeability for fractures, matrix and composite systemMaterial 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 wellsLink to unconventional reservoirs.
Secondary Recovery
Gas InjectionMaterial 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 aquifersLink 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 reservoirsUndiscovered naturally fractured reservoirs, why and how?Link to unconventional reservoirs. Economic Considerations for Naturally fracture Reservoirs Link to unconventional reservoirs.
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