Within the Guajira region of Colombia, several trillion cubic feet (TCF) of gas have been discovered, with the potential for additional reserves. Most of the discovered gas is present in two producing fields, Chuchupa and Ballena. Geologic considerations, including the nature of the stratigraphic column and low regional geothermal gradients, suggest that these gas accumulations are biogenic in origin. The geochemical character of the gas, which is both dry and isotopically light, further supports such an origin. A regional assessment suggests that future exploration also will be directed largely toward biogenic gas accumulations.

Unlike many assessments of hydrocarbon exploration potential that focus on trap capacity, this study examines the availability and character of hydrocarbon charge. The volume of hydrocarbons was estimated using a geochemical model in which the amount of bacterially produced gas is a function of organic enrichment and temperature history. The volume of gas available was constrained further by comparing the timing of gas generation to that of trap development. The overall expulsion, migration, and trapping efficiency of the hydrocarbon system was established through a statistical assessment of known gas accumulations in the Guajira region and ranged up to 3.2%. The estimated efficiency of the Guajira region hydrocarbon system is considered a minimum because of trap-capacity limitations. Using the trap-volume constrained system efficiency factor, the gas available to individual leads ranges up to 4 TCF. Additional upside potential may exist, given the uncertainties of the estimates. The presence of multi-TCF charge estimates clearly indicates the potential for additional commercial gas accumulations in the area.