"Yet, even though we have these huge increases in search rate per year, we still keep finding fewer and fewer reservoirs on average per year."

You are right indeed. Situation, when exploration well spudding is based on sisemic data only exists for a long time. Today, as it was decades before, oil companies drill mostly dry exploration wells. Drilling success rate doesn’t overcome 25% on average. It means that three dry wells go to waste from each four drilled. It means also that discovery occurs too slowly today, but there is a highly productive exploration technology (Seismo-electromagnetic - SEM) for detection of hydrocarbon deposits. It provides a success rate close to 75%. In other words, 3 productive wells for each dry well. Obviously with the technology like this world oil industry could make three times more oil discoveries then using conventional technology, and this technology won't need more investment,time-frame and so on compare to a conventional one. It would significantly mitigate world energy problems.

Seismics---Prospects---Drilling---Discoveries: one in four
Funding --------project time-----------------------------------------
SEM--------Prospects---Drilling---Discoveries: three in four
www.binaryseismoem.weebly.com

You have changed the straw's diameter, not the size of the glass.

Further, to the extent that discovery means 'new,' the wells are still going to be concentrated where the oil is - the problem being, the area of the globe where the oil isn't is pretty well known at this point.

Right, and the point is that we have more and more efficient ways of analyzing the smaller and smaller places left to discover oil. This is an example of rapidly exploring diminishing returns. A double-whammy, so to speak.