Abstract The Cantarell field, discovered in 1976, is one of the largest oil fields in the world. It is located on the continental shelf in the southern part of the Gulf of Mexico, in the east-central part of the Campeche slope, 80 km from Ciudad del Carmen, Campeche, Mexico. This oil giant is a mature field that has produced approximately 7.861 billion bbl of oil during 22 years of exploitation. It is made up of four blocks: Akal, Nohoch, Chac, and Kutz. The most important one is Akal, which contains more than 90% of the oil reserves. A total of 223 wells produces both heavy oil and gas from Upper Cretaceous carbonate breccia, using primary and secondary recovery methods. The possibility of the existence of a prospective hydrocarbon trap located below the Cantarell field was recognized in 1990, but because of the quality of geologic and geophysical data and the structural complexity of the area, no exploratory drilling was carried out. The final exploratory results indicate that the new discovery, Sihil, surpasses all the expectations of the thrusted block, exceeding by far the quantities of oil reserves established by previous paradigms. This discovery allows Pemex Exploration and Production [PEP] to establish a strategic plan to add even more hydrocarbon reserves using data provided by investigation of other underlying blocks.