I preface what I am about to write by noting that my undergraduate degree was in HISTORY, so my understanding of market dynamics maybe not be entirely accurate.
That said, as I understand it, the basic mechanism for falling prices is either: 1) level quantity of the commodity and a falling demand for the commodity, or 2) level demand with an increase in the amount of the commodity available. Either situation results in an oversupply of the commodity and downward pressure on the price.
Since 2) is approximately the current situation and OPEC is maintaining current production levels, where is the oversupply coming from? Non-OPEC oil producing states (principally the United States)?
As for the Saudis, I agree they do play the long game and can afford to protected as they are by their considerable sovereign wealth funds. Moreover, all of the Gulf States are very adroit in infiltrating and corrupting influential Western institutions (government, academic, and private). That's what makes them all so dangerous.
Combined with forcasted Global Demand to slow growth, while US/Canada production still forcast to grow.
EIA expects that global liquid fuels supply will continue to outpace consumption, resulting in an average stock build of 0.4 million bbl/d in 2015. Stock builds are expected to be concentrated in the first half of the year, averaging 0.7 million bbl/d during this period. EIA forecasts global liquid fuels supply to average 92.8 million bbl/d in 2015, 0.2 million bbl/d lower than in last month's STEO. The 2015 global demand forecast was also revised downward by 0.2 million bbl/d to an average of 92.3 million bbl/d, based on weaker global economic growth prospects for next year.