Oil exploration company Soco says it has found a 117m net pay section in its Te Giac Trang field well in Vietnam.
However, higher pressure than predicted in the formation has increased the weight of mud the company faces.
“Consequently a liner will now be run over the Miocene and Oligocene reservoir horizons,” the company said.
The H5 fault block is SOCO’s first of four well drilling programmes this year on the Te Giac Trang field.
The drilling started on 20 June and was estimated to take up to 30 days.
Meanwhile the company has also spudded an exploration well in the Lower Congo basin.
The London-listed firm began work on the well at the weekend to test potential of a post-salt structure off Pointe Noire, near where oil shows were found in 2009.
Drilling is expected to take up to 35 days to reach target depth for the find, which is part of the Sendji formation.