Maximising Oil Recovery and Reducing Water Cut in South Oman Fields: Results from Novel Organic Oil Recovery (OOR) Waterflooding Campaigns

Abstract This study includes the laboratory outcomes, process and the production results registered for two Organic Oil Recovery (OOR) waterflooding campaigns performed in two different fields. The aim of these treatments was to unlock residual oil, mobilise trapped/bypassed oil and to reduce water cut while maximising recovery in the waterflooded fields comprised by stacked clastic sandstone reservoirs located in South Oman. Reducing water cut is critical for extending the life for mature assets, as it helps to decrease OPEX associated with water disposal in addition to cutting emissions. OOR is a special tertiary oil recovery technique. This technology is based on the activation of targeted in-situ resident microbial ecology with the intent of increasing oil production. The mobility of trapped oil can be drastically increased by the microbial activation of specific species in the reservoir. The technique was implemented by pumping into the reservoir a custom-formulated nutrient mix directly to the injector wells, using typical pumping equipment. After the injection, the well is shut-in for a short incubation period and thereafter it can be returned to the normal injection schedule. Initial laboratory analysis in the producer wells demonstrated good ecology which confirmed the produced water had the required bacterial morphological traits to undergo the essential changes to become hydrophobic and facilitate oil movement. Field A was treated five times, one Pilot injection in a producer well and 4 waterflooding injections. The Pilot was performed in February 2021, with the first waterflooding injection in April 2022; and the 4th in March 2023. The two injections for Field B were completed in March and December of 2023 with both treatments having a significant impact in oil production. Field A had an increase in oil production of 15-25% after the Pilot. This field also presented a surge of ~60-75% in oil production, when compared to the average projected decline. For Field B an increase of ~19% in oil production was recorded after the first injection and ~50% rise after the second implementation. The biggest growth was seen in the well closest to the injector well in this case. A considerable reduction in water cut was also observed ranging between 6-15% decrease for some of the wells. Microbial activity was also noted, observing an ecology that recovered more rapidly and having a greater increase in the microbial count after the first implementations. These results proved that the application of this novel technology aided in the maximisation of the oil recovery for these fields in Oman by increasing microbial in-situ ecology suitable for release of trapped oil.