4. Basic Terms
• Porous Rock: Rock, which contains pores in it.
• Permeable Rock: Rock, which contains
interconnected pores in it.
• Source Rock: “Rock, which generate
hydrocarbons”.
• Reservoir Rock: “Porous and permeable rock
unit, which holds hydrocarbons”.
5. Seal or Roof rock
• An impermeable rock that acts as a barrier to
the passage of further upward migration of
Hydrocarbons, migrating in the subsurface.
• Common seals are:
– Shale
– Evaporites
• Seal overlies the reservoir rock to form a trap
or conduit.
• Also known as roof rock and cap rock
6. Pool
• An underground accumulation of petroleum
or gas usually forming a reservoir in porous
Sedimentary rock.
7. Trap
• A configuration or geometry of rocks suitable
for containing hydrocarbons, which is sealed
by a relatively impermeable formation
through which hydrocarbons will not migrate
8. Nomenclature of a Trap
• Crest or Culmination:
Highest point in the trap
• Spill point:
Lowest point of the trap up to which HC is
contained
• Spill Plane:
Horizontal contour cutting spill point
• Pay:
The productive reservoir i.e. vertical interval
of HC
10. Nomenclature of a Trap
• Closure:
Vertical distance from crest to spill plane
• Bottom water
Water zone immediately beneath the
petroleum reservoir
• Edge water:
Zone laterally adjacent to the reservoir
