Abstract
Abstract
The reservoirs developed in this work, BRF-KS, are giants in size, complex, highly mature, carbonate reservoirs undergoing waterflood. Given the long history of production and waterflood into the reservoirs, a key focus in the development philosophy was to maximize oil recovery using existing wells. Prior to this initiative, BRF-KS had reached a recovery factor of 38% with an already very high watercut of 98%. Due to being almost watered-out, a breakthrough was of utmost importance to extend the field’s life. It was predicted that many of the existing wells still have significant low-hanging oil behind casing, especially in the attic zone.
The key to rejuvenating these dark-brown reservoirs was through the redevelopment of the attic zone by performing shift-up and change-layer workovers. The campaign was started with a successful saturation logging job that located the presence of attic oil in Well-188, resulting in a production rate of > 200 BOPD after the zone was opened. This milestone was followed by a comprehensive and structured geological, petrophysical, engineering, and well integrity review of hundreds of the existing wells. Overall, 28 primary candidates were identified and proposed. To date, twenty-six jobs have been conducted, yielding encouraging results.
In general, the project was able to locate and unlock the attic oil, resulting in exceptional oil gain. The most phenomenal gain was achieved in Well-222, which produced an initial oil gain of more than 1200 BOPD after unlocking the preserved attic oil. Another historic output was observed in Well-362, where the watercut reduced from 99% to ~0%, resulting in an oil gain of more than 200 BOPD. In other wells, production enhancement was achieved while maintaining a relatively constant watercut. Overall, the ongoing campaign has enabled a production improvement with a maximum gain of 1210 BOPD, average initial well-by-well gain of 63 BOPD, and a reserve addition of 3.81 MMSTB. The remaining candidates are expected to contribute to these figures.
This paper elaborates on the journey of the past two years of the attic oil redevelopment campaign conducted in BRF-KS. The fit-for-purpose approach reported is applicable to a wide range of reservoir conditions, especially in brownfields at a very high watercut stage and under a low-oil price environment.