Changes

Traps charged during structural growth are not destroyed by spillage as long as the trapping geometry is maintained during deformation because petroleum migrates with the structural closure much faster than the rate of structural growth.<ref name=ch11r15>Hubbert, M., K., 1953, Entrapment of petroleum under hydrodynamic conditions: AAPG Bulletin, vol. 37, p. 1954–2026.</ref> Conversely, if structural closure is destroyed during deformation, spillage occurs rapidly.

Traps charged during structural growth are not destroyed by spillage as long as the trapping geometry is maintained during deformation because petroleum migrates with the structural closure much faster than the rate of structural growth.<ref name=ch11r15>Hubbert, M., K., 1953, Entrapment of petroleum under hydrodynamic conditions: AAPG Bulletin, vol. 37, p. 1954–2026.</ref> Conversely, if structural closure is destroyed during deformation, spillage occurs rapidly.

Paleofluid contacts may be tilted where spillage results from structural tilting. For example, Prudhoe Bay field, charged during the Late Cretaceous and tilted during the late Eocene<ref name=ch11r1>Atkinson, C., McGowen, J., Block, S., Lundell, L., Trumbly, P., 1990, Braidplain and deltaic reservoirs, Prudhoe Bay field, Alaska, in Barwis, J., McPherson, J., Studlick, J., eds., Sandstone Petroleum Reservoirs: New York, Springer-Verlag, p. 7–30.</ref> resulted in a tilted paleo oil-water contact.

Paleofluid contacts may be tilted where spillage results from structural tilting. For example, Prudhoe Bay field, charged during the Late Cretaceous and tilted during the late Eocene<ref name=ch11r1>Atkinson, C., McGowen, J., Block, S., Lundell, L., Trumbly, P., 1990, Braidplain and deltaic reservoirs, Prudhoe Bay field, Alaska, in Barwis, J., McPherson, J., Studlick, J., eds., Sandstone Petroleum Reservoirs: New York, Springer-Verlag, p. 7–30.</ref> resulted in a tilted paleo oil-water contact.

==Change in a fold trap==

==Change in a fold trap==

The figure below shows how continued growth of a foreland-sloping duplex preserves an accumulation in an early duplex but displaces the accumulation relative to the reservoir rock. The stippled area outlining the initial accumulation is fixed relative to the rock. The solid area on the lower figure marks the accumulation at the top of the structure after movement.

[[:file:predicting-preservation-and-destruction-of-accumulations_fig11-1.png|Figure 1]] shows how continued growth of a foreland-sloping duplex preserves an accumulation in an early duplex but displaces the accumulation relative to the reservoir rock. The stippled area outlining the initial accumulation is fixed relative to the rock. The solid area on the lower figure marks the accumulation at the top of the structure after movement.

[[file:predicting-preservation-and-destruction-of-accumulations_fig11-1.png|thumb|{{figure number|11-1}}Modified.]]

[[file:predicting-preservation-and-destruction-of-accumulations_fig11-2.png|thumb|{{figure number|2}}See text for explanation.]]

Similarly, where the axis of a fault-bend fold on a hanging wall is fixed relative to the bend of the fault on the foot wall, the actual rock occupying the fold changes during movement along the fault. However, the position of the trap remains approximately fixed relative to the footwall and the fault bend.

Similarly, where the axis of a fault-bend fold on a hanging wall is fixed relative to the bend of the fault on the foot wall, the actual rock occupying the fold changes during movement along the fault. However, the position of the trap remains approximately fixed relative to the footwall and the fault bend.

==Change in a fault trap==

==Change in a fault trap==

Traps in which faults form part of the closure are especially susceptible to spillage during structural growth because movement on the fault may result in leakage. Movement on the fault is also likely to juxtapose permeable lithologies across the fault at some point in the movement. The figure below shows spillage resulting from movement on a sealing fault.

Traps in which faults form part of the closure are especially susceptible to spillage during structural growth because movement on the fault may result in leakage. Movement on the fault is also likely to juxtapose permeable lithologies across the fault at some point in the movement. [[:file:predicting-preservation-and-destruction-of-accumulations_fig11-2.png|Figure 2]] shows spillage resulting from movement on a sealing fault.

 

[[file:predicting-preservation-and-destruction-of-accumulations_fig11-2.png|thumb|{{figure number|11-2}}See text for explanation.]]

As the fault displaces the units, an early charged trap (A, at t = 1) is juxtaposed against a sandstone at some later time (B, at t = 2). This probably will result in rapid spillage. If further fault movement restores favorable seal juxtaposition (C, at t = 3), additional petroleum charge will be needed to fill the new trap.

As the fault displaces the units, an early charged trap (A, at t = 1) is juxtaposed against a sandstone at some later time (B, at t = 2). This probably will result in rapid spillage. If further fault movement restores favorable seal juxtaposition (C, at t = 3), additional petroleum charge will be needed to fill the new trap.