Increasing Natural Dump-Flood Rate from High Pressure Aquifer to Low-Pressure Reservoir to Boost Oil Production Through Economical Shockwave Stimulation Technique

Abstract In a natural dump-flood well that has been progressing for approximately six years, observations were made that only one of the two intended low-pressure oil reservoirs – B2 and B3 reservoirs – is receiving water from the high-pressure aquifer in the same source well. The B2 reservoir which has benefited from the natural dump-flood has seen increasing reservoir pressure over the years and the off-take well commenced production two years after the commencement of the dump-flood. On the other hand, the pressure in the B3 reservoir remained stagnant and the off-take well for this reservoir remained idle throughout the six years of dump-flooding, indicating that crossflow from the dump-flood did not go into the B3 reservoir. Due to these observations, well stimulation through wireline-conveyed shockwave pulsing was selected to stimulate the near wellbore area of the injecting and receiving reservoir to address the issue. Identifying the root cause of the formation damage in the B3 reservoir is crucial in selecting the ideal method for well stimulation. Based on the available mineralogy test of the field, the formation damage was caused by fines migration due to the substantial amount of migrating fines including Plagioclase, Feldspars, Illites and Kaolinites which makes shockwave pulsing the optimal stimulation method to rectify the issue. During the execution, the shockwave pulsing tool was run inside the well with wireline and placed immediately across the perforation intervals of both the injecting and receiving reservoir. The stimulation was performed with an average pulse density of 60 pulses/foot throughout the entire perforations to remove the near wellbore formation damage. Three years after the well stimulation was executed, the pressure in the B3 reservoir was observed to increase from 650 psi to approximately 930 psi – a positive indication of successful dump-flood into the B3 reservoir. A further increase of the reservoir pressure was observed to 1050 psi one year later and the off-take well was finally brought back to production with an initial production rate of 500 bopd after being idle for more than 10 years. Several months later, the oil production rate keeps on increasing up to 850 bopd likely attributed to increasing reservoir pressure in the B3 reservoir as a result of the ongoing dump-flood from the high-pressure aquifer. This initiative has succeeded in re-activating an idle well through cost-effective well stimulation and secondary recovery technique as opposed to the more expensive option of acid stimulation and conventional water injection. This paper seeks to present the overall dump-flood mechanism, well stimulation technique selection criteria and detailed operation of the well intervention activity including lessons learnt and improvement plans which would be valuable for similar operations in the future.