Overproduction in Saudi Arabia is possible because there is oil recharge from underneath

Saudi Arabia deficit, low petroleum prices and the abiotic origin of hydrocarbons. 

"Saudi Arabia's budget deficit soared to $98bn (£65.7bn) this year as the world's biggest oil exporter counted the cost of falling crude prices. In the first budget under King Salman, the kingdom said revenues reached 608bn riyals (£108.7bn; $162bn), down 15% on official expectations. Spending for the year hit 975bn riyals, some 13% more than forecast. Oil prices have plunged from a five-year high of $125 a barrel in March 2012 to just $37.18 now. Saudi Arabia said that oil revenues, which make up 77% of the total revenue figure for 2015, are down 23% compared to last year." From BBC news, 28/12/15.

According to the abiotic oil hypothesis the available volumes of hydrocarbons, including oil and natural gas are practically unexhaustible. Throughout the Earth mantle and lower crust there are huge volumes of methane and other light hydrocarbons which gradually rise through fractures and accumulate when they reach impermeable layers. The abundance of petroleum means that the price will remain very low because of oversupply. The biotic theory, on the contrary, argues that petroleum is formed through the accumulation of organic matter (fossil fuel). Therefore prices will go upwards to a point in which other sources of energy will be necessary. Actual prices are in agreement with the abiotic theory. (D.Anton). 

http://www.bbc.com/news/business-35188807