LECTURE 14

LECTURE 14

1. HYDROCARBON TRAPS

   • a trap consists of volume of porous and permeable reservoir rock which is partially/completely enclosed by sealing rocks/pressure barriers
   • Types
     • Stratigraphic traps
       • Channel traps
       • Pinchout traps
       • Change in rock type
         • high risk (difficult identify rock types
       • Turbidite mound traps
       • Onlap traps
       • Reef traps
       • Unconformity traps
     • Structural traps
       • created by deformation of rocks. Concave-down pockets hold reservoir.
       • Salt dome
         • antiforms+other traps assoiciated with salt domes
         • deformation caused by salt movement-form many traps surround and overlying
       • Combination of fault and fold trap
         • common, higher risk (fault leak)
       • Deformations
         • Folding
           • antiformal trap
             • represent by closed contour,4-way dip closure (pericline)
             • most common, easy to find, low risk
             • bed of reservoir rock (overlain by seal rock) is folded into antiform-beds dip away from crest on both side-form antiform traps
         • Faulting
           • fault trap
             • shale gouge-shale smeared along fault plane by displacement
             • rare, higher risk (fault seal/leak)
     • Combination of structural+stratigraphic traps

2. GEOMETRIC ELEMENT

   • Crest
     • highest(shallowest) inside closed contour
   • Lowest closing contour (LCC)
     • deepest contour that still close. max. depth hcarbon can accmulation
   • Vertical Closure
     • Crest-LCC: max. gross vertical column of hydrocarbon trap can hold
   • Area closure
     • Area of LCC: max. area of an accumulation in a trap
   • Spill point
     • trap filled to LCC then further hydrocarbon will migrate through spill point
     • lie on LCC where contour start open
   • Stacked reservoirs
     • alternating reservoirs+seals in trap-multiple accumulation