Development Challenges in a Heavy Oil Field, Subject to Water Production: A Case Study of Diamond Field in Central Africa

The Diamond field from onshore in Gabon was brought into production by Perenco in 2000, but its development has mainly focused on deep light oil reservoirs. This study reassesses the potential of the shallow Senonian and Turonian reservoirs, which have remained underexploited due to technical challenges, including the presence of heavy oil (18-22 API) and significant water production. The results of structural modelling and petrophysical analysis (CMR) estimate a total oil in place (STOIIP) volume of 48 Mmstbo for the base case, rising to 718 Mmstbo in the high scenario. The analysis identifies 12 potential productive intervals, including six (6) in the light oil zone and six (6) in the heavy oil zone. Although the current recovery factor for the EM1 and LC2 zone is only 5.5 percent, as illustrated by the RK-3 wells historical production of 500,000 barrels in July 2010, the study shows that recovery rates of up to 40 percent are possible. Confirmation of these volumes, representing possible contingent resources of 287 Mmstb, now requires a dedicated appraisal phase to reduce structural uncertainties.