OSH November Drilling Report

[Kaliboo]

The Antelope 7 appraisal well was spudded on 2 November. At the end of the month, the well was at a depth of 1,302 metres and is currently running 13-3/8” casing before drilling ahead in a 12-¼” hole to test for the presence of a carbonate reservoir in the western flank of the field.

Is there anything we can glean from the 13-3/8" casing size down to 1,300 meters? This pic from Wike show a 13-3/8" casing to 4,000 feet leading to a 14,000+ foot TD hole.  https://upload.wikimedia.org/wikipedia/commons/d/d8/Casing-Diagram.jpg

casing shoe depths are determined by pore pressure and frac pressure gradients in the earth.  They tend to increase as you drill deeper so that requires an increase in mud weight.  A wide variation from well to well is an indication of very different geology or encountering steeply dipping beds of the same stuff at different depths.

In laymen's terms, I believe Kaliboo has stated that we cannot infer planned TD of this well based on what size casing has been set at the stated depth.

. Correct.  Recall is poor but I think I recall that we hit top of pay ~50-100 feet higher than expected in a well in the last 2 years.  I don't recall whether the base also was shifted up by a similar amount, but if so, then you can imply that the reservoir is maintaining constant thickness and sloping and infer that dip angle in the direction of the slope.  Erosion, scouring and other depositional processes can change the thickness.  That's how they project the top and bottom depths in the next wells.   The further away from existing well control, the less certain.  Presence of faults changes the whole picture and can dramatically change the pore pressure gradient.