Reservoir Eocene C/VLG-3676 of Ceuta field, one of the major reservoirs in Maracaibo lake basin, is characterized by operational challenges that prevent its optimal production. Drilling is challenging and requires large mud-weights to reach target.

In order to optimize drilling and completion operations, a geomechanical study was launched to develop a Mechanical Earth Model (MEM) and use it to improve well trajectory, mud-weight programs, and perforation strategies. The methodology followed when developing this MEM was: data audit and well selection; tectonics and structural-setting analysis; drilling-event analysis; mechanical-stratigraphy definition; rock-property evaluation; pore-pressure estimation; in-situ stress determination; wellbore-stability evaluation; mud-weight window determination; and optimal well trajectory computation.

The three most interesting features of this paper are: the analysis of more than 200 tests performed in laboratory on Eocene “C” cores that shows a very high degree of damage of the cored material; a new in-situ stress field determination method based on tectonic deformation theory; and a stress regime that changes from normal in the Miocene at shallow depths (200–5000′), to strike-slip and reverse in the Eocene at depths greater than 10,000′. This last result is of great importance for producing reservoirs in this area, as it not only impacts the evaluation of optimum mud-weight windows, but also well trajectories and perforation strategies.