1. Stratigraphic Traps – Sub-Unconformity & Reef
Upper Sand
Lower Sand
Slide 14
Here are two stratigraphic traps
On the left, cross-section on top and map view below
This represents a sub-unconformity style of trap
sands below the unconformity have a component of dip and form the reservoir
above the unconformity is a marine shale that provides the seal
here the big unknown often is how far downdip the sands contain HCs
On the right, cross-section on top and map view below
This represents an isolated reef
porous and permeable carbonate facies form the reservoir – often in the edges of the reef rather than the
central lagoonal facies
Again there has to be an adequate seal facies capping the reef A
Upper Sand A’ B B’
Lower Sand
Courtesy of ExxonMobil
L12 – Data Analysis