... anticlines ( Figure 1, (a )) , only a vertical seal, or caprock, is required; but faults (Figure 1, (b )) and stratigraphic traps ( Figure 1, (c,d )) must be sealed both vertically and laterally Figure 4. 1 ... reserves, cemented rocks, argillaceous rocks, chalk… (Figure 2) Figure 4. 2 General properties ° ° ° Permeability in seal are mostly < 1 0 -4 darcies Seal are important and commonly overlooked component ... (most ductile lithologies at top of column) THICKNESS ° A few inches of ordinary clay shale are theoretically adequate to trap very large column heights of hydrocarbons (particle size of 1 0 -4 mm...