After much consideration these are my conclusions in respect of interval 2867-3167m:
1/. The JV has not explained why it took 5 days to advance from 2867 to 3167m.
2/. This interval of the hole would include the Tikorangi Formation.
3/. The Tikorangi strata is carbonate [limestone] and at Matuku is perhaps 100m thick.
4/. Any drilling break [speeding up of drilling rate] or mud losses in a carbonate formation is significant as each indicates the carbonate may be fractured.
5/. Fractured carbonate is a potential hydrocarbon reservoir.
6/. It is extremely difficult to detect hydrocarbon in the fractured carbonate reservoir.
7/. Once fractured carbonate is detected it would be best practice that the driller then begin coring the interval.
8/. The most likely explanation for taking 5 days through 2867-3167m is that there was a drilling break in the Tikorangi and the driller switched over to coring the remainder of the formation.
9/. Subsequent to completion of the coring, the inspection of cores and downhole logging may have confirmed the presence of hydrocarbon: