Abstract The middle Eocene calcarenites from the Ku, Maloob and Zaap fields are formed by packstone-wackstone limestones of high porosity; 20%, permeability between 10 and 400 md and low shale content. They are formations with excellent petrophysical quality. The core data contains the following fossils groups: Globorotalia lenheri, Globorotalia spinulosa, Truncorotaloides rohri, Lepidocyclina antillea, Porticulasphaera Mexicana; wich all are representative of the Middle Eocene. There is also Wackestone and Mudstones textures and few illyte mineral precence. It presents a lowstand slope fan deposit. The area is limited by the ausence of the Calcarenite rocks and sismic interpretation, their vertical limit are the silicate rocks of the same age. The fields are pressure connected through a common aquifer. Within an open and connected system, with a normal hydraulic gradient, very close to 0.11 kg/cm2/m. The lower limits for the three fields are located at very close depth: 2720 TVDSS for Ku field, to 2710 TVDSS for Zaap field and 2750 TVDSS for Maloob.The oil production in the Middle Eocene Calcarenites reservoir (CCE) began in 1986 with the well Ku-10, which produces 17 ° API oil with viscosity of 8.5 cp. In previous studies The objective of the present study was to correctly identify the depth of the fluid contacts, which directly impacts on the reserves and increased the original volume of hydrocarbons; since the oil water contact was located about 200m deeper the original oil in place increased 200%. Also it rules out the possibility of compartments from previous studies.