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The Matoa field is a productive oil field located in the Salawati Basin. The field was discovered by the SEO-1X well in 1991 and reached peak oil production in 1994 with 9,752 BOPD. For over 30 years, the Matoa field has been explored to meet the hydrocarbon needs in the eastern region of Indonesia. The oil is produced from Intra Kais carbonate, which was deposited following the Sirga siliciclastic period. The latest study has identified two Intra Kais reservoir facies in this field, namely Intra Kais-I (middle Kais) which is associated with mound reefs, and Intra Kais-II (lower Kais) which is associated with pinnacle and mound reefs.

The primary oil is produced from the Intra Kais-I zone. The mound reefs of Intra Kais-I and -II are separated by a tight zone, as seen in the Matoa-2 well. However, in this well, Intra Kais-II is already a water zone. On the other hand, the pinnacle reef, as seen in the Matoa-29 well, shows that Intra Kais-I which is already producing oil overlaps onto the Intra Kais-II zone. Therefore, it can be inferred that the Intra Kais-II zone is likely to be a promising reservoir.

In our study, by generating seismic inversion using data from 20 wells, it has been possible to reveal the Intra Kais-I and Intra Kais-II reflectors more confidently than with conventional seismic amplitude techniques. Based on this understanding, a geological model has been constructed, which identified 12 million barrels of oil resources in the untapped Intra Kais-II zone.