dr daz, page-18

DB,
It would be an absolute waste of your time and money to get to the exact why. This sort of thing happens regularly in the industry. The drilling risk is always there.
It starts with the casing program design and how conservative or cheap you want to go. Uncertainties about the exact target depth and mud weight then may cause a lost circulation event to occur.
I have been categorically told they will consult an experienced drilling consultant next time which is, in itself pathetic.
To have lost circulation twice is dramatic and the cost are a test to that.
Bad drilling program but the real killer was management of risk at board level; plenty of blame to go around.