Sequence Stratigraphy of Blocks 102 & 106, Song Hong Basin, Vietnam

Blocks 102 & 106 are located in the Song Hong Basin, offshore Northern Vietnam in a water depth of 25 to 30 meters (Figure 1). Petronas Carigali Oversea Sdn. Bhd. (PCOSB) is the operator with a 50% interest. Other partners are PIDC (20%), SPC (20%) and ATIP (10%). Two dry wells have been drilled in Block 102 by the previous operator. In 2003 PCOSB drilled Yen-Tu 1X well in Block 106 with minor oil and gas discoveries and second well drilled in middle 2006 turned out to be dry well. A working petroleum system is believed to be present in the basin with couple of minor discoveries have been made in Blocks 102 & 106 and surroundings. As proven by the discovery of Yen Tu 1X and B10-STB-1X, source rock potential has the least risk. The lacustrine shale<br>deposited in the Oligocene syn-rift setting is believed to be the main potential for oil prone source rock. In addition, the early Miocene shallow marine shale and coal shows a good potential in generating oil and gas. In April 2006 XTG/XBS, PCSB carry out<br>Sequence Stratigraphic Study of Blocks 102 & 106 with the objective to understand the tectonic setting, basin formation, depositional model and the petroleum system of the area. In addition, this study aimed to answer the issue of correlation between Pretertiary Carbonate penetrated by Yen Tu 1X well and the exposed carbonate hills in Ha Long Bay (Figure 2). The correlation is crucial to establish analogue to the subsurface carbonate reservoir in Blocks 102 & 106. Plate tectonic reconstruction and geodynamic evolution shows that the Song Hong basin is a rift basin that formed in the late Eocene/Oligocene time. The basin formation and evolution is very closely related to the strike slip movements of the Red River Fault Zone. The basin has undergone a series of compressional and inversions events that provides the main structural framework for hydrocarbon trapping mechanism in the area. The study has identified eight sequence boundaries that separated the depositional package into eight sequences (Figure 3). The first package in the early Oligocene sequence is believed to be deposited in the lacustrine setting that provides the main potential source rock in the area. Seismic data and mapping shows that quite widespread of lacustrine setting during the early stage of the rifting that sufficient enough to have big lakes with low energy environment to be conducive for the deposition of good source rocks. The sediment inputs for lacustrine setting interpreted to be sourced from a multiple directions. However, during the early to late Miocene the deposition was controlled by marginal to shallow marine environments with the main sediment supply comes from the Red River in the northwest.