Try reading up on petroleum geology. Fossil fuels are derived from the remains of ancient dead plant and animal life, that fell and was buried into sedementary deposits. Then compressed and heated under enormous pressures and tempertures over millions of years. As a result you would expect to find fossil fuels primarily only in areas that experienced geological sedementary processes.
The deep Pacific ocean is not a canidate for supplies of fossil fuel sources because it is not a sedementary basin. Almost all sedementary basins have been explored for oil. There are some exceptions where enviromental treaties have prohibted exploration, where costs are too high for exploration, or the geology or terrain is too difficult to traverse; ie dense tropical jungle.
A signifigant case of potential massive new reserves is Antarctica, where a very old treaty that has not been reviewed in any real sense for 50 years has prohibited all exploration. Antarctica, although now entirely frozen and desolate was once, because of continetal drift, situated in a southern hemisphreric temperate zone, where large areas may have developed sedementary basins. Antarctica is frought with exploration and development challenges even if the prohibition was removed. Extreme cold (equipment won't work), remote location (absolutely no infrastrure), ice overburden movement and removal (think of having to clear a 1 square kilometer drilling site of 10 million cubic meters of densely packed ice half a kilometer in thickness). There could also be signifigant offshore Antarctic sedementary basins from ancient river delta's that could be explored with equal difficulty. These, however, are pristine ecological zones and oil drilling would cause massive extinctions and ecological damage at any potential drill site.
There will always be some oil available somewhere -if you have enough resources (and the will) to extract it. However, peak oil has arrived- oil production volumes are now beginning terminal decline.