The 'unrisked' is the maximum recoverable volume you could possibly have in all prospects, assuming they are full of oil or gas. The 'risked' is calculated by multiplying that unrisked number by a 'chance of sucess' factor, which represents a geologist's view of the chance of finding that resource. Here the chance of sucess used seems to be about 25% which is fairly standard (at least historically for most Niger Delta exploration). The numbers are also calculated to reflect the company's share of the resource, so they represent the gross resource multiplied by the equity share the company has in the license.
However note the caveat emptor on the top of the slide which says these are the pre-drill estimates. The drilling has added new information which is not reflected here, so these numbers are not current and therefore not meaningful. What is meaningful are the post-drill estimates, not yet made available. The statement in slide 14 'biogenic methane gas discovered across all ERHC blocks' unfortunatley may lead one to the conclusion that post-drill there will be little oil and I would guess a few tcf dry gas in total for all blocks. So what went wrong? Why the disappointing results? Was 25% chance of sucess realistic? It is possible the results shouldnt be particularly surprising since deep water drilling for oil really requires more sediment than may be present in JDZ. The reason is that you need to reach a certain temperature to preserve oil, otherwise it becomes biodegraded (ie. microbes still survive at cooler temperatures and chew through the oil to turn it to gas), its a big risk in GOM for instance, so you tend to try to go as deep as possible. I suspect that Chevron, Exxon and Anadarko came to this conclusion so exited. Judging by the drill depths and details of target sands Addax tested all the prospective sand sequences in the tertiary for the wells. So the chance of success was probably overly optimistic at 25%. Quite interesting that the gas is described as biogenic. That means it was not generated thermally, suggesting no active petroleum system which is very problematic. It may be interpreted as meaning there is no evidence of mature source rock in this part of the basin.
Total's involvement is interesting, certainly just to the north in there is a working petroleum system: JDZ1 (Obo) and OML 130 (Akpo and Egina) are evidence of this. It is likley that Total took on JDZ1 from Chevron as a possible extension for Akpo, I would be surprised if it was a high value deal however. Total may creep towards the rest of JDZ eventually, but the apparent lack of liquids may not be attractive to them. There's plenty of gas in Akpo which is being re-injected or piped to Bonny. Total are in the Bonny LNG plant too so see value from that side of the business.
Regarding the delay in announcing the commencement of phase 2, it is possible that nobody wants to drill another well there given the disappointment of the first round of drilling. So why not just withdraw right away and write it off? Well ONGC did just that. But knowing the Chinese penchant for hanging on to stuff in W Africa it may be more a tactic to retain the licenses without having to spend any more money on a new well. I suspect if JDA demand they drill another well in phase 2 then they may bail out.
This turned out ot be a rather long reply with lots of speculation so apologies on that. All of the above just my interpretation of the situation.
