Stratigraphic core wells ENRECA-1, -2 and -3: Results of the Song Ba rift, Phu Quoc island and Bach Long vi island drilling campaigns

Abstract

The long-term research co-operation between Vietnam and Denmark within basin analyses has generated many significant results. These have been used intensively in many ways including assessments of the hydrocarbon potential of the offshore basins, as input for license rounds, for promotion campaigns to attract industrial interest and for the publication of numerous scientific papers and presentations, which have contributed to the international appreciation of the fascinating geology of Vietnam.
Beside an extensive capacity building programme, one of the main activities of the ENRECA-programme has been the drilling of three stratigraphic core wells that have provided the research team with continuous cores of excellent quality, which have been analysed for sedimentary facies, source rock potential, age, petrography and reservoir properties.
The ENRECA-1 core-well was placed in the continental Song Ba rift in central Vietnam and cored 478m of the Oligocene (?) - Miocene fill of the rift. The cores document the variable depositional environments of the rift-fill. The most significant finding is the presence of two excellent lacustrine source rock successions, which have bearings on the occurrence of potential source rocks in the offshore Phu Khanh basin and thus the hydrocarbon potential of the basin.
The ENRECA-2 well was placed on the Phu Quoc island, where it cored 500m of Lower Cretaceous strata. The cores demonstrate the dominance of fluvial sandstones which in places show fair reservoir properties. Interbedded variegated mudstones were mainly formed in oxygenated lakes and flood plains and contain mostly inert organic matter.
The drilling of the ENRECA-3 well fulfilled an early proposal of coring the promising source rock bearing succession exposed in the Neogene inversion structure that forms the Bach Long Vi island. The cores document the presence of a minimum of 233m of excellent, world class oil-prone Palaeogene lacustrine source rocks. The source rocks are interbedded with various density current flow deposits including turbidites, hybrites and debrites, which together with sandstone dykes form an effective drainage system for hydrocarbons that may be generated where this prolifi c succession is deeper buried and matured.
The three strategically placed ENRECA core wells thus provided signifi cant new insight that is discussed below. The signing of a new Memorandum of Understanding (MOU) between VPI and GEUS will give the opportunity to their joint ENRECA research team to continue providing reliable and “demand-driven” research services to the public and industry in the years to come.