The Island of Trinidad is on the north flank of the Eastern Venezuela Tertiary basin. The structure and stratigraphy of Trinidad are similar to and continuous with those of eastern Venezuela.

The primary objectives for oil exploration in Trinidad are middle and upper Miocene deltaic sandstones. Hydrocarbon source rocks for these reservoirs are the underlying deep-marine shales of Paleocene through early Miocene age. Overlying Pliocene and Pleistocene sediments are primarily continental clastic deposits.

A proto-Orinoco delta system was present during Miocene time and prograded over Trinidad and the adjacent offshore areas. Isopach, seismic isochron, and facies studies have established the location of the delta depocenter offshore of the southern and eastern coasts. Rapid thinning of the deltaic units is evident north of the depocenter where the Miocene section is thin and lacking in sands.

Four structural provinces have been recognized in Trinidad: (1) the Northern High province, characterized by a shallow, complexly faulted basement; (2) the Diapiric Fold province, an east to northeast-trending zone of diapiric shale anticlines coincident with the Miocene delta front; (3) the Block Fault province characterized by north-northwest-trending growth faults coincident with the deltaic depocenter; and (4) the Monoclinal province, an area of regional north dip and sedimentary thickening from the Guayana shield into the deltaic depocenter.

Oil production is associated with the diapiric anticlines at the Miocene delta front. Gas production from the north-northwest-trending fault-block structures in the Miocene deltaic depocenter has been established. No significant production has been developed in the Northern High or Monoclinal provinces.