A six-month halt to most Libyan oil production is degrading its quality and raising the likelihood of volumes never recovering to previous levels.
A permanent reduction in exports would be a blow for the Mediterranean tanker trade.
Five eastern terminals were shut down in January by forces loyal to rebel warlord Khalifa Haftar and his Libyan National Army (LNA).
State producer National Oil Corp (NOC) called this blockade "a historic crime against the people of Libya".
Chairman Mustafa Sanalla said some of the damage is permanent and will never be repaired.
"Producing oil reservoirs that are shut down suddenly undergo mechanical, structural, chemical and even microbiological changes," he said.
Death of oil wells?
In a statement, he explained these changes can result in the "death" of oil wells.
Reservoir fluids, including oil, condensate and water, that had previously rested in equilibrium, may mix and form thick emulsions that restrict further production of oil, he added.
NOC is already expecting water encroachment at the Sara oil field, as well as a decrease in well productivity. Some wells will have to be shut, it said.
"In some fields, we are concerned about bacterial growth which will change the characteristics of the oil. Libyan oil is valued for being low in sulphur. The bacteria will raise the sulphur content, making it less valuable," Sanalla said.
Billions needed for repairs
Maintenance is being held up due in part to a lack of cash as the nation has lost $6.5bn in lost production.
Work to between 160 and 260 wells will cost somewhere between $50m and $100m, it is estimated.
Pipeline maintenance covering 6,760 km will bring this into the billions, NOC said.
The company also called on all Libyan groupings to allow an unnamed tanker on standby at Es Sider port to start loading crude oil from storage.
NOC demanded that all "foreign mercenaries" and armed militias leave the terminal immediately.
Vessel tracking data for the port does not reveal a tanker there at present.
Sanalla said NOC produced an average of 1.22m barrels per day (bpd) at the start of the year.
The company hoped to raise production to 2.1m bpd by 2024.
Output to fall to 2022
"We now estimate production will decline to 650,000 bpd in 2022, in the absence of an immediate restart of oil production and because of the state’s failure to provide the requested budgets to address the many challenges resulting from the blockade," Sanalla added.
After the UN-recognised Government of National Accord's (GNA) victories against the LNA in recent weeks, NOC has issued instructions for the export terminals to be ready for a resumption of operations.
Besides Es Sider, the ports are Hariga, Brega, Zueitina and Ras Lanuf.
UN-supervised talks on restarting production are continuing between NOC, the GNA and neighbouring countries backing the blockade.
