1. n. [Geology]

The structurally lowest point in a hydrocarbon trap that can retain hydrocarbons. Once a trap has been filled to its spill point, further storage or retention of hydrocarbons will not occur for lack of reservoir space within that trap. The hydrocarbons spill or leak out, and they continue to migrate until they are trapped elsewhere.

See: contour map,  migration,  reservoir,  structure,  trap