Changes

Thin but laterally extensive mud blankets, either deposited from hemipelagic settling or the muddy tails of turbidity flows, can form permeability barriers to vertical flow in these systems (e.g., Hempton et al., 2005). Shales representing maximum flooding surfaces are commonly permeability barriers. Large-scale debris flows also have the potential to form baffles and barriers. Shales can subdivide the reservoir into several hydraulic units (Lowry et al., 1993). In certain favorable circumstances, these blanket shales can lead to a more efficient recovery by encouraging edge-water drive and suppressing bottom-water influx into the basal perforations of production wells. This type of flow behavior can be recognized on the basis of formation tester pressure discontinuities (see Figure 112) and slow-rising oil-water contacts on pulsed neutron logs. A typical management strategy in deep-water reservoirs with extensive shales is to isolate water-producing perforations in production wells by setting a plug in the well opposite one of these shale barriers.

Thin but laterally extensive mud blankets, either deposited from hemipelagic settling or the muddy tails of turbidity flows, can form permeability barriers to vertical flow in these systems (e.g., Hempton et al., 2005). Shales representing maximum flooding surfaces are commonly permeability barriers. Large-scale debris flows also have the potential to form baffles and barriers. Shales can subdivide the reservoir into several hydraulic units (Lowry et al., 1993). In certain favorable circumstances, these blanket shales can lead to a more efficient recovery by encouraging edge-water drive and suppressing bottom-water influx into the basal perforations of production wells. This type of flow behavior can be recognized on the basis of formation tester pressure discontinuities (see Figure 112) and slow-rising oil-water contacts on pulsed neutron logs. A typical management strategy in deep-water reservoirs with extensive shales is to isolate water-producing perforations in production wells by setting a plug in the well opposite one of these shale barriers.

Water overrun above laterally extensive shales is a common feature in sheet complexes. Stranded oil can be found under these shales. Blanket shales also have the potential to form multiple attic oil targets under local structural culminations in deep-water sediments (Figure 194c).

Water overrun above laterally extensive shales is a common feature in sheet complexes. Stranded oil can be found under these shales. Blanket shales also have the potential to form multiple attic oil targets under local structural culminations in deep-water sediments ([[:File:M91FG194.JPG|Figure 2c]]).

Cellar oil targets can also occur (Figure 194d). Early sand input into a receiving basin tends to pond into the bathymetric lows. The seabed will eventually become smoother as the lows are filled in. Later sand flows will spill beyond the extent of the previous flows. These show a more tabular geometry and will be spread across a larger area than the underlying sediments, creating a fill and spill geometry. The ponded sand bodies can potentially hold isolated oil volumes by comparison to the more extensive later flows, which may be better swept.

Cellar oil targets can also occur ([[:File:M91FG194.JPG|Figure 2d]]). Early sand input into a receiving basin tends to pond into the bathymetric lows. The seabed will eventually become smoother as the lows are filled in. Later sand flows will spill beyond the extent of the previous flows. These show a more tabular geometry and will be spread across a larger area than the underlying sediments, creating a fill and spill geometry. The ponded sand bodies can potentially hold isolated oil volumes by comparison to the more extensive later flows, which may be better swept.