I'm not convinced that there are large oil reserves in Somalia.  There's no oil in neighborhing Kenya, and the only oil exploration in Ethiopia is in Gambella province, over near the Sudanese border, where you'd expect it.  (Sudan's oil reserves are mostly in the south.)

Yemen, across the Gulf of Aden from Somalia, has modest oil reserves, and if Somalia has any oil it's likely to be in the same general area, e.g. coastal and/or offshore.  

But Yemen's proven reserves are only around three billion barrels or less.  Even if Somalia has another three billion barrels, that's not really enough to set the world on fire.

I'm sure the companies would like the chance to explore for oil in Somalia, but even they must not be terribly optimistic about finding the hidden stash that will save the world (or at least them) from Peak Oil.  It's just not likely that there's much there.

Of course, I'm not an oil analyst either.  Who knows.