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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

Sequence Stratigraphic Approach to Identify Potential Stratigraphic Plays in Matured Blocks 01/02,Offshore Vietnam

Othman Ali Mahmud1; Irdawati Lokman1; Shamsudin Jirin1; Thang X. Tran1

(1) Exploration Division, PETRONAS, Kuala Lumpur, Malaysia.

Blocks 01&02 are located in the Cuu Long (Mekong) Basin, an early Tertiary rift basin offshore Southern Vietnam.

To date twenty-six (26) wells have been drilled which resulted in one producing oil field, three potentially commercial oil discoveries, one potentially commercial gas field and four dry wildcat wells. Hydrocarbons were found in the Pre-Tertiary basement and Miocene clastics intervals. In previous years, petroleum exploration in the Oligocene section of Blocks 01&02 was regarded as under-pursued after a series of drilling campaigns, which yielded no significant results due to poor reservoir quality.

With most of the structural traps tested by these wells, the blocks could be considered as mature. In pursuing further evaluation of the remaining potential of these blocks, a study based on a seismic sequence stratigraphic approach was carried out in 2008. The study was aimed at identifying potential stratigraphic plays and traps in Blocks 01&02 prior to relinquishment of the exploration Petroleum Sharing Contracts (PSC). At the same time, the study investigated hydrocarbon potential of Oligocene section in these blocks.

The study has identified six sequence boundaries which subdivide the sedimentary successions into five (5) sequences. The first three lower sequences are in the Oligocene interval while the other two in Miocene section. Biostratigraphic data suggests that the Oligocene sequences were deposited in the lacustrine setting while Early Miocene sequences deposited in the brackish to shallow marine environments. The potential source rock for petroleum system is believed from the lacustrine shales while the potential reservoirs for Oligocene sequences interpreted as fluvio deltaic sands in the lake setting and shallow lake sands. The Miocene sequences sharing similar potential source rock with Oligocene while the Miocene potential reservoirs spans from lacustrine to shallow marine sands.

Five potential stratigraphic plays were identified from the Oligocene interval in which out of five three are considered as in the moderate risk category in term of working petroleum system, while the other two are considered as in the high risk category.

This paper shall discuss the methodology and results of the study i.e., the identified stratigraphic plays and the hydrocarbon potential of the Oligocene section in Blocks 01&02, Cuu Long Basin, offshore Vietnam.