The drillship Stena Forth is drilling the well in 1,900 m (6,234 ft) of water.
According to the best estimate of NSAI’s report, the potential in GVN-1 is estimated at 235 MMbbl of oil with a 34% geological chance of success.
Preliminary drilling results are expected within 70 days, the company said.
Block 47 spans 2,350 sq km (907 sq mi).
Tullow is the operator and holds 50% of the rights in the block. Pluspetrol holds 30% and Ratio Petroleum holds 20% of the rights.