Santan Delta Evolution and Its Implication to The Petroleum System in North of Kutei Basin

Abstract

The presence of delta between Mahakam Delta and Sangatta Delta has been discussed before by several authors in Kutei Basin. However, there is no detailed information of its location and stratigraphic successions. Our recent sequence stratigraphic studies, utilizing multi vintage seismic and well-based data in East Kalimantan & Attaka Working Area, provide new insights into the evolution of Santan Delta and its implication to the petroleum system in our working area. The Santan Delta might have been overlooked as a potential sediment source for reservoirs in the north of Mahakam Delta. Since the 1970’s, more than 50 MMBOE of hydrocarbons have been produced in this area from Late Miocene – Pliocene deltaic reservoirs. Santan Delta development started in early of Late Miocene which was indicated by fluvio-deltaic sedimentation prograde to the east. Kuching High to the west of the delta started to undergo uplift. Santan Delta development achieved peak sedimentation at the end of Late Miocene – Early Pliocene which was indicated by the presence of significant deltaic facies. It also pushed the carbonate sedimentation to the shelf margin area. Later in Late Pliocene, the presence of Santan Delta started to diminish which is shown by presence of shelfal carbonates that retrograde or backstep to younger shelf margin in this area. The stratigraphic succession of the Santan Delta deposited in Late Miocene – Pliocene became important to better understand source rock, reservoir, and seal distribution in its surrounding deltaic, shelf, slope, and deep-water environments.