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