Assessment of the areal and vertical sweep efficiency in cyclic carbonate reservoirs of the middle east - A case study from a mature field

Carbonate reservoirs contain almost half of the world's hydrocarbon proven reserves. Because of the horizontal and vertical heterogeneities present in cyclic carbonate reservoirs, more than 50% of the oil in these rocks is trapped or bypassed and yet to be recovered, even after water injection. This fact by itself motivated researchers to investigate ways to improve the recovery factors by implementing new recovery schemes coupled with advanced well designs and completions. This paper aims to analyze the value of adding ICDs (In Flow Control Devices) in horizontal wells to improve the areal and vertical sweep efficiency and the recovery factor. A high resolution mechanistic model was built for a large carbonate reservoir in X-Field, with the aim to capture the small scale sedimentary and diagenetic cycles, including the dense stylolitic intervals. Geostatistical algorithms were implemented to propagate the petrophysical properties within a sequence stratigraphic framework. The 3D static model was built based on real field data, using several wells. However, for the purpose of the simulation work done in this study, only a crestal oil producer and a downflank water injector in a line drive system with different completion strategies is analyzed. Different sensitivities were then studied in order to investigate the impact of various reservoir descriptions and multiple well completions, involving vertical wells, standard horizontal wells and horizontal wells with ICDs, on the overall sweep efficiency and recovery factor. This work showed that changing the fluid injection/production rates as well as completion intervals is not the only controls to achieve higher recovery factors. By implementing smart completions with ICDs and proper well placement, higher volumetric sweep efficiencies were achieved, resulting in an incremental gain of 9% recovery factor.