The Pacific coastal basin of Columbia covers an area of approximately 56,000 km² between the Pacific Ocean and the Western Cordillera. Another basin of deposition--the Pacific shelf basin--lies offshore and west of the coastal basin and comprises an even larger area. These basins are the least-explored, potentially petroliferous areas in Colombia. Only 6 wells (2 offshore, 4 inland) have been drilled; 3 are in the northern Atrato area of the basin. A partial reason for lack of exploration is the relative inaccessibility of the area, one of the most humid and unhealthy tropical rainforest zones in the western hemisphere.

Unsuccessful results may also be traced to the lack of a concentrated effort at deciphering the regional geology. Surface geology does not everywhere accurately reflect the subsurface picture; in many places it masks the true underground structure.

The Pacific coastal basin is currently regarded as one of promising potential for a country that badly needs to find new oil to meet ever-rising demands. Seismic investigations and photogeologic work permitted the mapping of a body of igneous and metamorphic rocks that crop out between the Docampado and Baudo Rivers in the central or San Juan area of the basin (San Juan paleohigh).

The petroleum potential of the area also appears clear, considering that sediments in excess of 20,000 ft (6,100 m) have accumulated in the basin, and that possible source rocks of both Tertiary and Late Cretaceous age occur within the sedimentary area. Furthermore, numerous oil and gas seeps have been reported throughout, and previously drilled wells, though not commercial, had encouraging oil and gas shows.