Trap/Reservoir/Seal Flashcards
a naturally occurring storage area, characteristically a folded rock formation, such as an anticline, that traps and holds petroleum
Reservoir
Characteristics of an Economically Viable Reservoir
- Rock must be permeable.
- The volume of trap petroleum must be sufficient.
- The reservoir is not too compartmentalized.
Intrinsic Properties of a Reservoir
- Net to Gross
- Porosity
- Permeability
- Hydrocarbon Saturation
measure of potentially productive part of a reservoir. Expressed as percentage of producible reservoir within the overall reservoir package.
Net to gross
the void spaces in the rock, measured as
volume percentage or a fraction
Porosity
the ability of a material (rock) to transmit fluids
Permeability
most commonly, reservoirs contains both oil and water. It is rare to find a reservoir with pure oil or gas.
Hydrocarbon Saturation
most common reservoir lithologies
- sandstone
- limestone
- dolomite
Sandstone Depositional Environment
a. Alluvial Fans
b. Aeolian Dunes
c. Lakes
d. Fluvial Systems
e. Deltas
f. Shallow Marine Systems
g. Submarine Fans
Limestone and Dolomite
a. Shelfal/Ramp Carbonates
b. Reefs
c. Deep Water Carbonates
d. Dolomite
e. Karst
any geometric arrangement of rock, regardless of origin, that permits significant accumulation of oil and/or gas in the subsurface
Trap
Three (3) Types of Traps
- Structural Trap
- Stratigraphic Trap
- Hydrodynamic Trap
may be generated through tectonic, diapiric, compactional, and gravitational processes; the range of of this traps in a basin can be deduced from knowledge of the basin evolution.
Structural Trap
Traps formed by Compressive Tectonic Processes
- Anticline
- Folds
- Faults
Traps formed by Extensional Tectonic Processes
- Rift Basin
- Faults
Traps formed by Diapiric Processes
Salt Diapir and Mud Diapir
sometimes referred to as subtle
traps, are formed by lithological variations imparted to a sediment at deposition or generated subsequently by alteration of the sediment or fluid through diagenesis.
Stratigraphic Trap
the fundamental part of the trap, which prevents the petroleum from migrating onward through the rock—as a bucket without holes
Seal
caused by differences in water pressures associated with water flow, which creates tilt on the contacts between hydrocarbons and water. Consequently, the fluid contacts in this traps do not correspond directly to structural maps of the reservoir.
Hydrodynamic Trap
Lithologic Attributes of Seal
- Small Pore Sizes
- High Ductility
- Large Thickness
- Wide Lateral Extent
Five (5) Types of Seal
- Membrane Seal
- Hydraulic Seal
- Faults
- Trap Fill
- Pressure Seal
capillary pressure is simply the difference between the pressure in the wetting phase
(normally water) and that in the non wetting phase (normally hydrocarbon).
Membrane Seal
seals in which petroleum can escape
only by creating fractures
Hydraulic Seal
can act as both conduits (migration pathways) and seals, depending on the hydraulic conditions, the rock properties of the faults, and the properties of the rocks juxtaposed across the fault.
Faults
if there is an effective seal that prevents
petroleum loss, petroleum traps can be filled to capacity
Trap Fill
seals relate to the trapping of petroleum, and may result in no-flow conditions for the petroleum over geologic time.
Pressure Seal
a process whereby petroleum moves from its place of origin, the source rock, to its destruction at the Earth’s surface.
Migration
Three (3) Types of Migration
- Primary
- Secondary
- Tertiary
includes leakage, seepage, dissipation, and
alteration of petroleum as it reaches the Earth’s surface
Tertiary
movement out of the fine-grained source
into a more permeable conduit.
Primary
movement from a permeable unit into
the reservoir
Secondary
