The direction leading most directly to higher elevations on an inclined stratum or structure. 

Anticline:   

A hydrocarbon trap formed by the upward bowing of strata into a dome or arch. 

American Petroleum Institute.

A well drilled to determine the extent of hydrocarbons discovered inprevious well on the same structure. 

The unit of volume measurement used for petroleum and its products. 1 barrel = 42 U.S. Gallons = 35 Imperial Gallons (approx.) or 159 litres (approx.) 

A depression of large size in which sediments have accumulated. 

Sedimentary rocks composed of calcium and/or magnesium carbonate e.g. limestone, chalk. 

A sedimentary rock composed predominantly of particles less than silt size usually comprising clay minerals. 

The area within the lowest closing contour of a structure, also, a closed structure. See four-way dip closure.