Complex acid-solvent treatment design and practice for Jurassic-Cretaceous carbonate formation of the Varadero oilfield (the Republic of Cuba)

Abstract

Petroleum generation in the North Cuba Basin is primarily the result of thrust loading of Jurassic and Cretaceous source rocks during formation of the North Cuba fold and thrust belt in the Late Cretaceous to Paleogene. The fold and thrust belt formed as Cuban arc-forearc rocks along the leading edge of the Caribbean plate translated northward during the opening of the Yucatan Basin and collided with the passive margin of southern North America in the Paleogene. Petroleum fluids generated during thrust loading migrated vertically into complex structures in the fold and thrust belt, into structures in the foreland basin, and possibly into carbonate reservoirs along the margins of the Yucatan and Bahama carbonate platforms. The U.S. Geological Survey defined a Jurassic-Cretaceous Composite Total Petroleum System (TPS) and three assessment units (AU)-North Cuba Fold and Thrust Belt AU, North Cuba Foreland Basin AU, and the North Cuba Platform Margin Carbonate AU-within this TPS based mainly on structure and reservoir type. There is considerable geologic uncertainty as to the extent of petroleum migration that might have occurred within this TPS to form potential petroleum accumulations. Taking this geologic uncertainty into account, especially in the offshore area, the mean volume of undiscovered oil in the composite TPS of the North Cuba Basin is estimated to be 4.6 billion barrels of oil (BBO), and the mean ranges from an F95 probability of 1 BBO to an F5 probability of 9 BBO. The mean volume of undiscovered gas is about 9.8 trillion cubic feet of gas (TCFG), and of this total, 8.6 TCFG is associated with oil fields, and about 1.2 TCFG is estimated to be gas in nonassociated gas fields in the North Cuba Foreland Basin AU.