Optimizing seismic attribute to unlock facies change at Eocene-Oligocene fluvial deltaic sandstones of Pematang formation: Case study the "m" field, Central Sumatera Basin

The "M" Field is in the Northern most of the Oil Prolific Central Sumatera Basin at Barumun sub-Basin. The field was originally discovered by drilling M-1 well. This well became the first well proving up the presence of hydrocarbon at Pematang Formation in this region. Pematang Formation is unique because it can serve as reservoir rock as well as source rock. The MX reservoir is part of the Pematang Formation. Based on the last drilling data in which it flows 200 barrels of oil. However, the sand of this reservoir disappeared at the other well, even though the location is not too far. This paper addresses the strategic approaches to interpret facies change using Acoustic Impedance (AI) Inversion. The facies change is detected using AI. It is challenging reservoir since its individual thickness is below seismic resolution. Geologically the MX reservoir was deposited under fluvial deltaic lacustrine environment. The result shows that M-2 is in the delta front facies while the M-1 is in the pro-delta facies. Even though only 1.6 km distance between M-2 and M-1 well cause significant facies change. Result of this study is useful for determining development drilling program in this field.