Reservoirs C4 and C5 belong to the VLA-6/9/21 area of the Lagomar Segregation, and are located in the East Flank of the Block I, Lagunillas field, Lake of Maracaibo Basin, Western Venezuela. The C sands correspond to the Misoa formation of Eocene age. For the present study, 25 wells of the area were selected, 12 of which belong to a special Integral Field Laboratory, and have enough information that allowed the generation of a model that can be extrapolated to other wells in the field. Using all this information, certainty maps for each reservoir were constructed. Pore throat radius was estimated from porosity and permeability data from conventional core analysis, along with capillary pressure data. Winland’s equation, an empirical relationship between porosity, air permeability and pore throat radius corresponding to a mercury saturation of 35%, was used for reservoir C5. In 1992, Winland’s work was modified by Pittman, and for reservoir C4, the R45 Pittman equation was applied. Cementation and saturation exponents (m, n) for C4 and C5, were determined from core analyses. The resistivity of the formation water (Rw) was estimated from chemical analyses and by the SP curve method. Clay volume (Vsh) was obtained using Larionov’s tertiary rocks model, which correlated well with X-Ray difraction analyses. Once the key wells were evaluated using the Waxman-Smits water saturation model, which resulted in a good match between core and log data, the evaluation was extrapolated to the other new and old wells of the area. Five different rock types were identified: Mega, Macro, Meso, Micro, Nanno, and were used to construct cross-sections showing their lateral distribution. Flow units were identified using the Modified Lorenz Plot and the Vertical Flow and Storage Diagram. Rock type areal distribution maps were also constructed, and have an excellent agreement with the sedimentary facies maps obtained from the sedimentological study.