The studied reservoir has one of the greatest heavy-oil reserves (OOIP about 12.2 MMMSTB) in the Maracaibo Lake basin. It has been largely developed except for one coastline area (385 km2), which includes both zones’ land and shallow water. Limited access of conventional drilling rigs in the area, coupled with low definition of the structural, stratigraphic, and petrophysical model have reduced drilling activities.
Plans have been made to increase production by 20% through drilling of wells in the coastline area. This plan requires the consideration of multiple variables, such as new surface facilities, drilling rigs for both geographical environments, rock heterogeneity, compartmentalized structure (6 blocks), low number of drilled wells (8 wells), and limited reservoir data, which will generate a large number of development scenarios.
This paper presents a probabilistic production forecasting of the coastline reserves through an innovative approach based on a systematic evaluation of risk and uncertainty of reservoir variables, and a maximization of net present value (NPV). The optimization of a large number of decision variables, such as the type of drilling rigs, type of wells completion, and seismic acquisition zone, was obtained. The optimal stochastic scenario showed a NPV with a 340% increase compared with the best deterministic scenario.
This approach triggered warnings about the current plans for seismic data acquisition, which proved to be uneconomical despite expected improvements in the geological and stratigraphic framework. Therefore, the drilling of stratigraphic wells becomes an alternative to partially substitute seismic survey.
Finally, the different operational scenarios showed that development should be done in stages and by geographical areas, starting with stratigraphic deviated wells into shallow water zone using conventional rigs, then vertical and slanted wells in shallow water zone using swamp rigs, and verticals and slanted wells in the ground region using land rigs.