The Tarapoa Block (previously City Block) contains over 20 fields. Annual production peaked at close to 60 000 b/d in 2004.The operator has discovered and brought online several small areas since 2011 and is still focused on exploration drilling. The producing reservoir in the Tarapoa Block is the Upper Cretaceous Napo formation. The Napo comprises three reservoir zones: the 'M1' sands which overlie the Upper and Lower 'U' sandstones which in turn overlie the 'T' sandstones. The 'M1' sand is the primary reservoir.