Abstract During 2006 we drilled 3 horizontal wells in Chuchupa field, a large gas offshore reservoir in the Colombian Caribbean Sea. The drilling campaign included drilling, logging, pressure testing, and coring a pilot vertical hole, which was key in improving our reservoir characterization. The reservoir thickness and petrophysical parameters found were better than expected and the new information reduced the uncertainty on the Original Gas In Place (OGIP). These wells increased the production potential for this field significantly. Current cumulative gas in Chuchupa is 2.5 Tscf, equivalent to 400 Million barrels of oil. The field has 7 horizontal, 7 slanted and 1 vertical production wells located on 2 production platforms. We formed a multidisciplinary team to design the optimal development plan for Chuchupa. The team included geoscientists; reservoir, production, drilling, completion, and facilities engineers; decision analysts; and commercial and planning professionals. We performed seismic re-interpretation, petrophyscial evaluation, geologic modeling, and integrated-reservoir-to-surface simulation. The study resulted in a set of static and dynamic models that were used to generate a phased development that consisted of 3 new horizontal wells and installation of a compression system. The 3 proposed horizontal wells were successfully drilled and completed and field production capacity increased by 250 MMscf/D. We have produced 203 Bscf from these wells after three years. We acquired 330 ft of core in the vertical pilot hole with 100% recovery. We found 60 ft of additional gas column, with average porosity and permeability of 30% and 6 Darcies respectively. Rigorous production- and pressure-history match supported the revaluation of OGIP range from 4.1-5.3 Tscf to 5.0-5.6 Tscf. Integration of various disciplines, detailed planning, good execution, and use of robust coupled reservoir-surface tools resulted in a successful development project that increased reserves and production potential significantly. The added capacity and additional reserves supported the implementation of compression installed in 2009. The obtained results allow Chuchupa to continue being an important player in supplying the gas demand in this north corner of South America.