This thesis investigates a tight overpressured Cretaceous carbonate formation in Field A of Mexico. The Cretaceous carbonate was penetrated by well A1 and tested oil successfully during an open-hole test covering interval 5356 to 5515 m (MD) that produced oil of 33 degrees API. Initial pressure was 1050 kg/cm2 at 5,227 m (14,934.51 psi at 17,144 ft) that diminished gradually to 450 kg/cm2 (6,400.5 psi). Oil rates varied between 2,200 and 300 bopd. The observed production decline is not economical, given the depth of the reservoir. Field A has log data from 9 wells and 2 re-entered wells. Well logs have been used to investigate the Cretaceous carbonates using a methodology that includes the evaluation of matrix and fracture porosities with a petrophysical dual-porosity model, water saturation, permeability, capillary pressure, pore throat apertures and rock fabric number. Rock fabric evaluation focuses on determining grainstone, packstone and wackestone-mudstone rocks using a rock fabric number. Pattern recognition in Pickett plots is used as part of the analysis. Well A1 was production-tested. Unfortunately, there were some unplanned shut-ins, but it was observed that the original static pressure of the reservoir was not restored following short flow periods. Buildup periods were evaluated with a modified dual-porosity model with restricted interporosity flow due to partial secondary mineralization in the fractures. The evaluation permitted estimating several parameters of interest, including fracture transmissivity, storativity ratio, skin and the extrapolated pressure (p*). The testing suggests that although natural microfractures are present, they tend to close once the well goes on production. Fracture permeabilities (k2) from well testing are very low, in the order of 0.02 md and tend to decrease during subsequent tests; this indicates the carbonate reservoir is tight and stress-dependent. All the information is integrated for estimating Petroleum Initially in Place (PIIP) and reserves. It is concluded that there is oil potential in the Middle Cretaceous carbonate in Field A, which can be tested with horizontal wells and multi-stage hydraulic fracturing. These types of drilling and completion will be required, given that the results of the study indicate that the Middle Cretaceous carbonate is tight.