Tullow’s C1 well, in a basin margin location in the east of the CB-ON-1 block, was spudded to a total depth of 1,916m. The main objective sands between approximately 650m and 750m were present as predicted but proved to be water-bearing based on petrophysical log evaluation and pressure gradient data.
Minor gas shows were encountered in a deeper claystone-siltstone sequence; however, the objective sand in this sequence was poorly developed and could not be logged as hole stability problems in the lower part of the well prevented the logging tools passing below 1,183m. Consequently, the precise extent and quality of this sand could not be determined.
This is the first well in a campaign which will comprise at least four wells, targeting multiple play types within the block. The John Energy 20 rig will now move to drill the G1 target, which will test a separate play area to the north of the block. Drilling on the G1 well is expected to commence by mid-August 2008 and has an anticipated duration of 30 days.
