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Fracture traps are divided into three classes: extension, shear, and complex, based on the internal characteristics and geometry of the fractures that make up the reservoir. The outline below shows the classes, some subclasses, and possible styles into which these traps may be subdivided.
Fracture traps are divided into three classes: extension, shear, and complex, based on the internal characteristics and geometry of the fractures that make up the reservoir. The outline below shows the classes, some subclasses, and possible styles into which these traps may be subdivided.
==Outline==
==Outline==
{| class = "wikitable"
|-
! Regime || Class || Subclass || Style
|-
| rowspan = 12 | ''Fracture trap''; Lateral boundaries of the trap are provided by change from fractured reservoir to unfractured or less fractured rock or by change from open, permeable fractures to cement-filled or narrow-aperture, low-permeability fractures. || rowspan = 4 | ''Extension fracture trap''; Dominant reservoir fractures are extension fractures. || rowspan = 2 | ''Parallel fractures''; Open fractures in a fractured reservoir, predominantly unidirectional in both strike and dip. || ''Mineralized fracture''; Partially or totally mineralized by postfracture cements, typically calcite, gypsum, or silica.
|-
| ''Nonmineralized fracture''; Contains no postfracture cements or minerals.
|-
| rowspan = 2 | ''Intersecting fractures''; Open fractures in fractured reservoir of several intersecting sets, either along fracture strike or fracture dip. || ''Mineralized fracture''
|-
| ''Nonmineralized fracture''
|-
| rowspan = 4 | ''Shear fracture trap''; The dominant reservoir fractures are shear fractures. || rowspan = 2 | ''Parallel fractures'' || ''Mineralized fracture''
|-
| ''Nonmineralized fracture''
|-
| rowspan = 2 | ''Intersecting fractures'' || ''Mineralized fracture''
|-
| ''Nonmineralized fracture''
|-
| rowspan = 4 | Complex fracture trap; Dominant reservoir fractures are complex fractures. || rowspan = 2 | ''Parallel fractures'' || ''Mineralized fracture''
|-
| ''Nonmineralized fracture''
|-
| rowspan = 2 | ''Intersecting fractures'' || ''Mineralized fracture''
|-
| ''Nonmineralized fracture''
|}
'''Regime:''' Fracture trap<br>
'''Regime:''' Fracture trap<br>
Lateral boundaries of the trap are provided by change from fractured reservoir to unfractured or less fractured rock or by change from open, permeable fractures to cement-filled or narrow-aperture, low-[[permeability]] fractures.
Lateral boundaries of the trap are provided by change from fractured reservoir to unfractured or less fractured rock or by change from open, permeable fractures to cement-filled or narrow-aperture, low-[[permeability]] fractures.